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THE EFFECT OF POST-STORAGE TEMPERATURES
AND
FREEZE/THAW CYCLES
ON REGROWTH PERFORMANCE OF
BARE-ROOT HERBACEOUS PERENNIALS

By
Ralph William Heiden

A THESIS

Submitted to
Michigan State University
in partial fulfillment of the requirements
for the degree of

MASTER OF SCIENCE

Department of Horticulture

1987

ABSTRACT
THE EFFECT OF POST-STORAGE TEMPERATURES
AND
FREEZE/THAW CYCLES

ON REGROWTH PERFORMANCE OF
BARE-ROOT HERBACEOUS PERENNIALS

By
Ralph William Heiden

Exposure of bare-root herbaceous perennials to
post-storage temperatures of 10°C for up to 3 weeks and
20°C for one week after 5 months’ storage at 0 or -2°C,
did not significantly affect the regrowth quality of
the 12 species tested compared to controls. Only four
of the species showed a significant decline in regrowth
quality following 2 or 3 weeks at 20°C. 0n the basis
of these results, it appears that bare-root perennials
may withstand limited exposure to elevated post-storage
temperatures provided that they are packaged properly
to prevent desiccation.

No significant loss in regrowth quality was
observed in 4 of 6 species of bare-root perennials
subjected to 6 freeze/thaw cycles with each cycle
consisting of one week at 1°C followed by one week at
—3°C. For the other two species, both considered
"difficult-to—store", exposure to more than one cycle
caused a significant decline in regrowth quality and

survival rate.

DEDICATION
To my wife, Margo, for her patience and support

as I take this detour in life.

11

ACKNOWLEDGMENTS

I would like to thank my major professor, Dr.
Arthur Cameron for his patience, guidance, support and
friendship throughout my graduate career.

Dr. Irvin Widders and Dr. Julian Lee also
deserve my appreciation for their input and comments on
my manuscript.

Anne Richards, Cindy Klobucher, Roy Lefevre,
Mohamad Maqbool, Sharon Pupkiewicz and Charles
Robinson all provided assistance in my research for
which I am truly grateful.

A special thank you to Jane Waldron for her
help with the final draft.

Finally, I would like to thank Mr. Dennis
Walters of Walters Gardens, Inc. of Zeeland, Michigan
for providing the plant material used in the research

and for his friendly support.

111

TABLE OF CONTENTS

Page
INTRODUCTION ..................................... 1
LITERATURE REVIEW ................................. 6

CHAPTER I
POST-STORAGE HANDLING OF BARE-ROOT HERBACEOUS

PERENNIALS
Introduction ................................ 22
Materials and Methods ...................... . 24
Results ..................................... 28
Discussion ............... .... ............... 65

CHAPTER II

IMPACT OF ALTERNATING CYCLES OF FREEZING AND
THAWING TEMPERATURES ON THE REGROWTH OF BARE-
ROOT HERBACEOUS PERENNIALS.

Introduction ................................ 73
Materials and Methods ...................... . 74
Results ..... ... ............................. 76
Discussion .................................. 82
BIBLIOGRAPHY ...................................... 85
APPENDIX .......................................... 89

iv

LIST OF TABLES

Table Page
CHAPTER I

1.1. Mean 4 week regrowth ratings of Aquilegia as
influenced by 3 days at various shipping
temperatures and averaged over all holding
temperatures and weeks....................... 31

1.2. Mean 4 week regrowth quality rating for
Dicentra as influenced by different holding
temperatureSOOOOO0.00.0.00.........OOOOOOOOOO 35

1.3. Mean 4 week regrowth ratings of Artemisia at
4 weeks as influenced by 1 to 3 weeks post-
storage duration averaged over shipping and
holding temperatures. The main effect was
significant at the .000 level and the 2—way
interaction was not significant.............. 57

1.4. Mean 4 week regrowth ratings of Artemisia
as averaged over weeks and shipping
temperatures. The main effect was significant
at the .000 level and the 2-way interaction
was not significant.......................... 58

1.5. Mean 4 week regrowth ratings of Salvia as
influenced by time over 0, 10 and 20°C holding
temperatures. The main effect was significant
at the .041 level and the interaction was not
significant.................................. 60

1.6. Mean 4 week regrowth ratings of Salvia as
influenced by temperatures averaged over 1, 2 and
3 weeks in holding. The main effect was
significant at the .013 level and the
interaction was not significant.............. 60

1.7. Mean percentage of bare-root plants exhibiting
etiolated growth upon visual inspection prior
to potting as effected by shipping temperatures
during Experiment 1 .......................... 62

Table Page

1.8. Mean percentage of bare—root plants exhibiting
etiolated growth upon visual inspection prior
to potting as effected by holding temperatures
during Experiment 1.. ...... .................. 62

1.9 Mean percentage of bare-roots exhibiting
etiolated growth upon visual inspection prior
to potting as affected by weeks in holding
temperatures during Experiment 1............. 63

1.10. Mean percentage of bare-roots exhibiting
etiolated growth upon visual inspection prior
to potting as effected by weeks in storage
during Experiment 2.......................... 63

1.11. Mean percentage of bare-roots exhibiting
etiolated growth upon visual inspection prior
to potting as effected by holding temperatures
during Experiment 2.......................... 64

1.12. Relative sensitivity of herbaceous perennials to
exposure to holding temperatures of 10 and 20° C
for 2- 3 weeks based on regrowth quality following
storage...................................... 67

1.13. Relative sensitivity of herbaceous perennials
to exposure to a holding temperature of 30° C for
1- 2 weeks based on regrowth following
storage ..................................... 68

CHAPTER _I_;

2.1. Mean 4 week regrowth ratings of surviving
plants of Coreopsis and Geum as influenced by
storage in alternating temperature cycles
consisting of one week at 1° C and one week at

-30 Cocoa00000000000000.00000000000000.0000... 77

vi

LIST OF FIGURES

Figure Page
CHAPTER I
1.1. Relationship between 4 week regrowth rating of

Aquilegia and length of exposure to different
holding temperatures averaged over 3 shipping
temperatures.... ........ ....... ..... .......... 30

1.2. Mean four week regrowth rating of Artemisia
following 3 days at different shipping
temperatures and 1 to 3 weeks at different holding
temperatures.... ..... ......................... 34

1.3. Four week regrowth rating of Asclepias
following 3 days at different shipping
temperatures and 1 to 3 weeks at different
holding temperatures .......................... 38

1.4a. Four week regrowth rating of surviving
plants of Asclepias following 3 days at different
shipping temperatures and 1 to 3 weeks at
different holding temperatures................ 40

1.4b. Percent survival of Asclepias following
3 days at different shipping temperatures and 1 to
3 weeks at different holding temperatures..... 40

1.5. Relationship between 4 week regrowth rating
and time in holding temperatures of Phlox
subulata averaged over the 3 shipping
temperatures....... ....... .................... 43

1.6a. Four week regrowth rating of Coreopsis
following 3 days at different shipping
temperatures and 1 to 3 weeks at different
holding temperatures.............. ........ .... 45

1.6b. Four week regrowth rating of surviving plants
of Coreopsis following 3 days at different
shipping temperatures and 1 to 3 weeks at
different holding temperatures ............ .... 45

1.7. Percent survival of Coreopsis following 3

days at different shipping temperatures and 1
to 3 weeks at different holding temperatures.. 47

vii

Figure Page

1.8a. Relationship between 4 week regrowth
rating and time in holding temperatures for
Achillea.. ..... ........ ........ ............... 51

1.8b. Relationship between 4 week regrowth rating
of surviving plants only and time in holding
temperatures for Achillea..................... 51

1.9a. Relationship between 4 week regrowth rating
and time in holding temperatures for Phlox
paniculata..0...OOOOOOOOOOOOOOOOOOO0.000...... 53

1.9b. Relationship between 4 week regrowth rating
of surviving plants only and time in holding
temperatures for Phlox paniculata............. 53

1.10a. Relationship between 4 week regrowth rating
and time in holding temperatures for Sedum.... 56

1.10b. Relationship between 4 week regrowth rating
of surviving plants only and time in holding
temperatures for Sedum .............. .......... 56

CHAPTER I;

2.1. Effect of exposure to freeze/thaw cycles

(1°C for one week: —3°C for one week) during

storage on the 4 week mean regrowth ratings of
Coreopsis, Geum, Hemerocallis, Hosta, Lupine

and Monarda ... ...... ... ...... ............... 79
2.2 Effect of exposure to Freeze/Thaw Cycles
(1°C for one week; -3°C for one week) on the

mean regrowth ratings and percent survival of
Coreopsis, Geum, Hemerocallis, Hosta, Lupine
and Monarda.. ...... ........ ..... ............. 81

viii

Introduction

Herbaceous perennials include a large number of
species and varieties of plants in which the foliage
generally dies back to the ground following a killing
frost in the fall. These plants are grown in the
garden as ornamentals for their flowers or foliage.
Commercially, herbaceous perennials are often field-
grown and harvested in the fall or spring. Spring
harvested plants may be sold and replanted immediately
while those lifted in the fall are placed in
refrigerated storage bare-root plants. From winter to
spring, the plants are removed from storage and
distributed to wholesale and retail outlets or directly
to the consumer. The bare-roots are then either potted
for sale or may be planted for establishment in garden
beds.

Each year, millions of bare-roots representing
thousands of species and varieties are successfully
handled by growers using traditional storage
techniques. However, growers still receive complaints
from customers who find that a significant percentage
of the stored material is in poor condition or does not
perform as expected in the garden (Walters Gardens,
Wayside Gardens, personal communications).

Several major problems manifest themselves

following long—term storage of herbaceous perennials.

The most visibly apparent of these is the poor physical
appearance of the bare-roots caused by severe
desiccation or the presence of molds and rots (personal
observations). Maqbool (28) identified desiccation as
a major factor in poor regrowth performance of stored
bare-roots. Depending on the degree of moisture loss,
plants may survive and regrow, but the negative initial
impression on the customer may be long lasting.

In some cases, the plants do not attain an
acceptable regrowth quality following potting or
planting in the garden. One difficult situation occurs
when bare-roots appear healthy upon visual inspection
but fail to regrow when planted. Undefined
physiological factors or internal pathological agents
may prevent the plants from becoming re-established.

Determining the cause(s) of these problems is
complicated by the fact that thousands of species and
varieties of herbaceous perennials are commonly
produced for the trade. As noted by Mahlstede and
Fletcher (26), ideal storage requirements vary from
species to species and may even be different for
varieties within a single species.

Very little systematic research has been done on
the storage and handling of herbaceous perennials.
Therefore, the exact cause and effect relationships
between storage conditions and regrowth potential and

ultimate plant quality remain largely undefined. In

1960, Mahlstede and Fletcher (26) outlined some basic
prerequisites for successful storage for many
herbaceous perennials. Key among these were the
employment of refrigerated storage to control
temperature fluctuations and the use of polyethylene
films for moisture retention. Among individual growers,
however, the degree to which these early
recommendations are followed varies greatly. Although
some growers have made specific refinements on these
techniques based on trial and error studies, the
results of their work are not generally available.

Maqbool (28) conducted experiments on long-term
storage of herbaceous perennials i.e. from the time the
bare-root plants are harvested in the fall until they
are removed for shipment to retail outlets. He found
that desiccation of the bare—roots was a key factor in
subsequent regrowth quality of the plants. Generally,
after plants lost 10-20% of their weight through
desiccation, regrowth ratings declined drastically.
Use of polyethylene films during storage greatly
reduced the occurrence of moisture loss. He also
determined that many perennials will store well under a
variety of temperatures ranging from -2 to 5°C
(26)(28).

Although it has been shown that maintenance of
low storage temperatures and the prevention of

desiccation by the use of polyethylene wraps will help

maintain quality of plants during the long-term storage
period, problems still occur when the plant reaches the
consumer. Low survival rates and poor regrowth quality
continue to occur in a certain percentage of the plants
marketed annually.

Additional research is needed to adequately
identify those factors or steps in the storage process
which may be contributing to a reduction in regrowth
quality of bare-root herbaceous perennials. One area
of concern is that period between removal from the
initial, generally long—term, storage and receipt by
the ultimate consumer. This "post-storage" phase often
includes long-distance shipping and a holding period
when the plants must await potting or retail sale.
During post-storage handling, the plants may be
subjected to a variety of temperatures and relative
humidities for up to 3 weeks or more. The bare-roots
may encounter stresses which could be detrimental to
subsequent survival and regrowth potential.

Another area for investigation is the impact of
temperature fluctuations during the storage process. Of
specific concern are temperature fluctuations during
storage involving below to above freezing temperature
exposures. During the months between harvest and
retail sale, plants may be shifted between storage
areas with differing temperature levels or may be

shipped in non-refrigerated conveyances and then

re-stored. It is not uncommon for bare-roots to be
exposed to one or more shifts between temperatures
below and above freezing as part of the storage
process.

In order to determine if temperature shifts might
account for the poor performance of certain perennials
as reported by growers, two sets of experiments were
conducted. Regrowth quality of several species and
varieties of herbaceous perennials was analyzed
following exposure to: 1) a number of post-storage
temperatures over varying periods of time: and 2)
several cycles of storage in temperatures above and
below 0°C. In each case, with the exception of
temperature level, the plants were stored in accordance
with generally accepted storage conditions.
Polyethylene films were used to prevent moisture loss,

a critical element in storage success (28).

Literature Review

Mahlstede and Fletcher (26) made one of the first
attempts to define proper handling and storage
procedures for bare—root herbaceous perennials. They
reported a 1953 study by Mr. George Rose of the Henry
Field Seed and Nursery Company which examined the
impact of several storage methods on the quality and
regrowth ability of a number of herbaceous perennials.
Bare-root plants were stored in polyethylene bags
(sealed or unsealed) at one of three temperature
regimes which included frozen storage at -2.2 to -1.1
°C, cold-room storage at 1.1 to 4.4°C and common
storage at 10 to 18.3°C.

Following storage, each plant was rated on
criteria such as keeping quality, appearance, presence
of molds, need for trimming and presence of etiolated
growth. The results showed a wide range of responses
over the individual species tested but certain trends
were delineated which applied to groups of species.
For instance, Ageratum L., Convallaria L. and
Platycodon DC had high ratings following storage in
sealed bags under all of the temperature treatments
while Coreopsis L., Chrysanthemum coccineum L. and
Aster L. received low ratings regardless of treatment.
The results, however, may have been influenced when the

bare-roots were removed from storage for the initial

rating and then were returned for additional storage
prior to the final rating. If, in fact, the tissue was
frozen, this may have allowed it to thaw before being
refrozen which may have contributed to the decline in
regrowth ratings for some species.

Mahlstede and Fletcher (26) developed a
classification system for storage of herbaceous
perennials based on groupings of plants with similar
physical structure i.e. root type, and uniformity of
response to handling and storage techniques. The
system, however, was supported by limited data and
included only a small percentage of the total number of
species and varieties commonly stored as bare-roots

(26).

Moisture Content gt Harvest

Mahlstede and Fletcher (26) stated that successful
storage of bare-root herbaceous perennials may be
associated with the condition of the plants at the time
of harvest. They reported that poor storage results
were obtained when strawberry runners were "excessively
succulent" at the time of packaging although this term
was not defined. It was suggested that maturity and
moisture content of the plants are key factors.
However, limited attempts at artificially drying stock
prior to storage were not successful (see 26). They

estimated that a reduction in moisture content of

8

between 12 and 54% did not reduce storage success
although no supportive data was given (26)(27).
Reduced moisture contents for stored woody
ornamentals may be achieved by cutting back on the
irrigation of the crop in the field during late summer
or early fall (10). This will presumably increase the
level of hardiness but care must be taken to avoid
stressing the plant (10). However, it seems unlikely
that this technique could be utilized for herbaceous
perennials grown under Michigan conditions where
difficulties often arise due to excessive fall

rainfall.

Physiological Status 33 Harvest

Several researchers have demonstrated that timing
of harvest can influence storage success of strawberry
(2), conifer seedlings (35) and deciduous plants (11).
In red—osier dogwood, Cornus sericea L., the earliest
harvestable stage of development has been defined as
vegetative maturity i.e. that point at which plants may
undergo chemical defoliation and still be expected to
survive winter storage (11). g. sericea plants placed
in cold-storage following this stage survived for long
periods without injury (11).

Starch content at the time of harvest has been
proposed as an indicator of physiological maturity for

pine seedlings (18), roses (48) and strawberry runners

(9). Freeman and Pepin (9) found that several varieties
of strawberry runners stored better when harvested
after mid-November in the Pacific Northwest. They
observed that the starch content of the root cortex was
generally low in early fall, increased by mid-November
and then declined throughout the winter.

Anderson and Gutteridge (3) found that mean
maximum daily temperatures of less than 10°C and
minimums of less than 5°C in the field 3 days prior to
lifting improved the survival of fall harvested
strawberry runners. They state that the later the
lifting date, the better the survival rate after
storage under climatic conditions in Great Britain.
Maqbool, Richards and Cameron (unpublished) found
similar results on herbaceous perennials grown in
Michigan.

Ritchie et a1 (35) reported that Pacific Northwest
nurserymen recognize a "window" during the fall harvest
period in which bare-root conifer seedlings attain
their optimum physiological condition for lifting and
storage. Determining the timing of this optimum harvest
period is complicated by the substantial physiological
heterogeneity among seedlings of various seed lots and
by climatic variations from year to year (35). They
found that certain conifer seedlings' ability to

withstand desiccation stress during storage appears to

10

be linked to the degree of dormancy attained at lifting
time (35).

To date, no reliable method has been developed to
enable growers to quickly determine the earliest
optimum date for lifting strawberry runners (2) or

herbaceous perennials.

Rate 9: Cooling

 

For many horticultural commodities including
strawberry runners (5), vegetables and fruits (49), the
rate at which the material is brought to the desired
storage temperature is an extremely important factor in
successful storage. The heat of respiration must be
removed by exposure to low temperatures and adequate
air circulation around storage crates during the
initial cooling period (22).

Mahlstede and Fletcher (26) harvested delphiniums
in early fall at 25°C and packed them in polyethylene
lined crates. Plants at the center of the crate took 14
hours to reach the storage temperature of 1.1°C while
those near the outer edges reached the desired
temperature in only 3 hours. Mahlstede (25) found
that rotting was more apparent at the center of the
crates of stored perennials which took 13-15 hours to
cool from 25°C to 1.1°C. Under Michigan conditions
where plants are often harvested from mid-October to

December, initial cooling requirements may not be so

11

great since soil temperatures are usually less than 5-

10°C (Richards, unpublished).

Storage Temperatures Levels

Few investigations have been published regarding
the ideal storage temperatures for bare-root herbaceous
perennials. Mahlstede and Fletcher (26) observed that
most perennials are held commercially in refrigerated
storage at a freezing temperature of -2.8 to -1.1°C
while some may be safely stored at refrigerated
temperatures between 0.6 to 4.4°C. Common storage at
10 to 18.3°C was successfully used for short periods of
time when plants were healed into sand or other
material (26).

Maqbool (28) found no significant difference in
regrowth quality of bare-root herbaceous perennials
following 6 months storage at -2 or 0°C. Many of the
perennials tested did equally well following 6 months
at -2, 2 and 5°C. All plants attained poor regrowth
quality following -5°C storage and none survived
storage at —10°C.

Some species such as Chrysanthemum maximum appear
to have quite specific temperature requirements. Bare-
root plants of this species achieved acceptable
regrowth quality only at the single temperature level
of 2°C. The current recommendation is to store bare-

root perennials at or near 0°C (28).

12

Low storage temperatures can minimize the rates of
respiration, metabolic activity, mold development and
other physiological reactions (28). Tree seedlings of
many species are commonly stored at a range of
temperatures between -2 and 2°C since , survivability
is reduced at —5°C (1)(8). Asparagus plants are stored
commercially at —2.2 to 0°C (47). Most of the
literature on storage of bare-root strawberry runners
indicate an optimum temperature range of between —1.1
and 0°C (2)(3)(5)(14)(44).

Rooted cuttings of the herbaceous perennial
Teucrium chamaedrys stored well in closed polyethylene
bags at 1.1°C for 167 days but were unsatisfactory in
terms of regrowth quality when stored at -0.6°C (38).
Worthington and Smith (47) found that no bud growth
occurred in asparagus plants stored for 10 weeks at
0°C. However, one week at 15.6°C following cold
storage resulted in bud growth on plants stored in
polyethylene although the amount of this etiolated

growth was not objectionable (47).

Temperature Fluctuations

Olien (31) found that winter killing of barley
plants in Michigan involves direct freezing injury i.e.
intracellular freezing. This occurred most commonly
during winters in which there had been a midwinter thaw

followed by a return to subfreezing temperatures.

13

Thomas and Lazenby (42) determined that repeated
freezing and thawing could be expected to increase
injury to Festuca arundinacea L. but only within a
critical temperature zone specific to the plant and its
physiological state. They determined that some grass
varieties seem to be more sensitive to repeated
freezing than were others.

Mader and Feldman (24) found that strawberry
runners subjected to alternating freezing and thawing
temperatures (-3 and 3°C) underwent a "physiological
weakening" as indicated by decreasing levels of sugars
and starches. These plants had a higher mortality rate
when planted in the field compared to plants held at a
constant storage temperature.

Gul and Allan (13) reported a higher survival rate
for plants subjected to gradual rather than a rapid

temperature change during freezing and thawing in

winter wheat.

Water Relations

Fretz and Smith (10) suggested that the control of
relative humidity is perhaps the single most important
factor in successful storage of woody ornamental plants
due to the difficulty in maintaining levels of 95-98%
in commercial storage units. Robinson, et a1 (36)
found that the reduction of temperature is the most

important factor to successful storage of vegetables

14

and soft fruits but it is followed closely by the need

to minimize evaporative losses.

Shrinkage losses of vegetables are almost entirely

due to evaporation from the surface (16). The amount
evaporation which can occur is limited by the amount
water which the air can hold. A reduction in water
loss can be achieved by decreasing the temperature
while maintaining a constant moisture content and/or
increasing the moisture in the environment at a
constant temperature (36).

Mahlstede (25) found, however, that desiccation
controlled drying out of plant material prior to
packaging for storage could improve the keeping
quality of bare-root herbaceous perennials. If field

conditions at harvest were excessively wet, allowing

of
of

by

by

the plants to lose some moisture prior to storage would

often result in improved field survival. This type of

prestorage curing is also commonly used with tulips and

other bulbs as recommended in the Holland Bulb Forcer's

Guide.

Mahlstede and Fletcher (26) could not correlate

moisture loss from fall harvested and stored bare-roots

of carnations, delphiniums, strawberries and hybrid tea

roses with their subsequent survival rate in the field.

Maqbool (28) found a highly significant inverse

linear relationship between regrowth quality and water

loss for a range of bare-root perennials. A

15

mathematical model based on transpiration rates was
developed by Cameron and Maqbool (6) which showed
that, for Phlox subulata, the regrowth grade would be
expected to drop to zero i.e. death, after 4 days of
exposure to 15°C with 50% relative humidity. It would
take 11 days for the plants to drop to a zero rating if
exposed to 0°C at that humidity level. However, plants
could be stored successfully for several months at 15°
C if the relative humidity were maintained at 98% or
higher. Maqbool (28) recommended the use of 4 mil
polyethylene films to provide a high relative humidity
to provide high regrowth quality of bare—root

herbaceous.

Free Moisture

Moistened packing materials such as shingletow,
sawdust, peat moss or excelsior are often used to
maintain the water content of stored bare-root plants
(27). Worthington and Scott (46) and Duffield and Eide
(8) found that if this material is excessively wet it
may promote the development of molds on bare-roots.

Mahlstede and Kirk (27) attributed poor storage
quality of strawberry runners to two factors: a)
excessively succulent plants containing an abundance of
moisture at the time of packaging; and b) a large
quantity of free moisture in the package (27). Stuart

(40) found that Easter lily bulbs stored in wet packing

16

media resulted in a nearly 40% decrease in salable

blooms compared to bulbs stored in dryer peat.

Polymeric Films

Anderson (2) stated that the use of polyethylene
was one of the most significant advances to facilitate
the cold storage of plant material. Polyethylene and
other plastic wraps are used to prevent moisture loss
in fruits and vegetables (15)(16)(17)(27), tree
seedlings (1)(19), strawberry runners (5) and
herbaceous perennials (28).

Polyethylene films are manufactured in thicknesses
ranging from .001 to .005 inch and have differing
permeabilities to water vapor, carbon dioxide, oxygen
and ethylene. Thus, commodities packed in plastic may
be subjected to conditions of higher humidity, higher
concentrations of carbon dioxide and ethylene and lower
concentrations of oxygen than those to which unpacked
commodities are exposed (15)(17)(27)(40)(41).

Condensation on the inside of polyethylene films
tends to encourage the development of molds on stored
bare—root plants (46). Factors which contribute to
condensation include high relative humidities caused by
transpiration, heat produced by the plant material and
inconsistent temperature control in the storage

facility (43)(47).

17

Mahlstede and Fletcher (26) recommended the use
of polyethylene bags for the storage of bare-root
perennials to retard moisture loss. Maqbool (28) found
that the beneficial effects of storing bare—root
herbaceous perennials in 4 mil polyethylene bags
exceeded any potentially negative effects from
condensation, modified atmosphere or impaired rate of
heat exchange.

Packing materials such as shingletow, peat moss,
excelsior or sawdust have a dual purpose: 1) to retard
moisture loss; and 2) to provide a cushioning effect to
prevent injury to the plants during transit (20).
Several studies have shown that sphagnum moss or
similar packaging materials are not necessary for the
storage of strawberry runners when poly bags are used
(2)(46). Including root packing materials such as peat,
hydromulch or sphagnum soaked in water provided no
improvement over bare-root storage of Fraser fir
seedlings (19). For Easter lilies, 20-30% moisture
(considered dry) in peat packing materials in poly
lined crates at -0.5°C resulted in longer storage life

(41).

Poly Bag Ventilation

Ryall and Werner (37) found that the presence of
a limited number of holes in a sealed polyethylene bag

would not allow air exchange to significantly decrease

18

the internal humidity level. However, oxygen and
carbon dioxide movement are greatly enhanced by the
presence of a relatively small number of perforations
(Shirazi, unpublished results).

Poly liners tend to retard heat exchange (26).
Tomato seedlings shipped in poly lined crates averaged
1.2-1.8 degrees C warmer enroute and on arrival than
did plants packed without film (29). Tomato seedlings
which have a high rate of respiration survived best
with ventilation holes in the poly liners while those
without ventilation experienced excessive heating and
poorer survival rates (29).

Mahlstede (25) stored several species of
herbaceous perennials in ventilated or sealed poly bags
and found that species varied in their response
depending on the storage temperature. Those stored at
subzero temperatures responded positively to sealed
bags while either ventilated or sealed bags could be
used in above—freezing storage. Sealed bags were
recommended for Alcea, Artemisia schmidtiana and
Platycodon which were prepackaged and stored at 4.4°C.

In later studies, Maqbool (28) recommended the
use of unsealed polyethylene bags or liners containing
a few perforations for the long-term storage of bare-
root herbaceous perennials. This allows for more rapid
initial cooling and reduces condensation while

maintaining a high humidity level inside the bag.

19
Pathogens

Fungal infections are a major cause of loss in
the storage of strawberry runners (2) and Lockhart (22)
found that rapid cooling to storage temperatures is
important in minimizing mold development. According to
Worthington and Scott (46), desiccated runners are more
susceptible to decay but factors such as dormancy, soil
on the plants and excessive moisture in packaging
materials are also conducive to decay development (46).

Temperature is often a factor in mold development
in conifer seedlings but Duffield and Eide (8) found
that storage at 0 to 1.7°C resulted in freedom from
molds. A storage temperature of —3°C inhibited mold
development on Fraser fir seedlings even when the
foliage was wet at the time of packing (19).

Maqbool (28) studied the effect of pre-storage
fungicide application on the regrowth quality of a
number of species of herbaceous perennials.
Applications of fungicides always reduced the extent of
mold coverage over 6 months of storage. However,
fungicides had either no effect or were detrimental to
the regrowth quality of the perennials tested. The
most susceptible plants to this phytotoxic effect were
those stored with green tops such as Iberis
sempervirens and Lavandula angustifolia. On the basis

of these experiments, he could not recommend the

20

general use of fungicides for the control of storage
molds.

Maqbool (28) also found that even when 50% of the
surface of the bare-root plants were covered with
surface molds, no direct impact on regrowth quality was
observed. A higher degree of coverage or the presence
of soft rotting molds, bacterial infections and,
perhaps, physiological breakdowns did have a level of
detrimental impact on cold-stored bare-root herbaceous

perennials.

CHAPTER l

Post-Storage Handling 2: Bare-Root

 

 

Herbaceous Perennials

21

 

w
E

Introduction

Herbaceous perennials are often field—grown,
harvested in the fall as bare-root plants and stored
for varying periods of time by commercial growers. As
orders are processed, the bare-root plants are removed
from storage and shipped to the retail outlet where
they are either held for future delivery or potted for
sale.

Millions of bare-root herbaceous plants
representing of thousands of species and varieties are
successfully stored each year. Still, growers,
wholesalers and retailers of herbaceous perennials
report that a significant percentage of the plants
harvested each fall lose quality before they reach the
consumer (Walters Gardens, Wayside Gardens, personal
communications).

It has been postulated that temperature
fluctuations during the "post-storage period" i.e.
between removal from long-term storage and delivery to
the customer, may prove detrimental to the regrowth
potential and ultimate quality of the plants.
Temperatures during this period may reach 30-35°C with
20°C exposure being fairly common. Bare-root plants are
also removed frequently from storage at -2°C, exposed
to high temperatures and then returned to -2°C for
additional storage or shipping (personal communications
Wayside Gardens and Walters Gardens).

22

 

1‘6

3C

23

It is well established that low temperatures can
minimize processes such as respiration rate, metabolic
activity, mold development and other physiological
reactions which contribute to successful storage (28).
Mahlstede and Fletcher (26) reported that bare-root
perennials were routinely stored at temperatures
ranging from —2.8 to 4.4°C depending on the types
involved. Maqbool (28) reported that -2 to 5°C storage
temperatures were optimum for many bare—root herbaceous
perennials. The effects of elevated storage
temperatures on this type of plant material have not
been studied.

Maqbool (28) also established the paramount
importance of the prevention of moisture loss during
the storage period although this factor was not always
considered in earlier storage temperature work. Bare-
root plants in the experiments discussed here were kept
in polyethylene films during storage in order to
minimize desiccation and to isolate the effect of the
temperature fluctuations independent of moisture loss.
The specific intent was to determine how quickly and to
what degree plant regrowth quality might decline in
response to being held at elevated temperatures up to

30°C during this post—storage period.

e]

1‘6

Materials and Methods

Experiment 1

One year old plants were harvested in late
November of 1984 and were stored through March, 1985.
Eight species of herbaceous perennials were used
including Aquilegia (Aquilegia ’McKana Hybrid)’,
Artemisia (Artemisia schmidtiana ’Silver Mound’),
Asclepias (Asclepias tuberosa), Coreopsis (Coreopsis
grandiflora ’Sunray’), Dicentra (Dicentra spectabilis),
Geum (Geum chiloense ’Lady Strathden’), Lavandula
(Lavandula angustifolia ’Hidcote Blue’) and Phlox
subulata (Phlox subulata ’Emerald Pink’). The plant
material was taken to the campus in East Lansing
following harvest and processing at Walters Gardens in
Zeeland, Michigan.

The bare-root plants were divided into treatment
units consisting of 6 plants from each of the eight
species and placed in bulk-packed 4 mil polyethylene
bags which were packed into wooden celery crates. The
plant material was then stored for 5 months at -2°C in
controlled environment rooms.

Upon removal from storage, 39 crates were divided
into 3 groups which were placed at 5, 10 or 20°C for 3
days. This was intended to simulate conditions
experienced during shipping from the wholesaler to the

retailer.

24

 

 

0(

25

After 3 days of exposure to higher temperatures,
one crate of plants from each temperature was planted
in the greenhouse. The remaining 36 crates were divided
equally between holding temperatures of -2, 5, 10 or
20°C. After 1, 2 or 3 weeks of simulated holding
period, one group of plants were removed from each
treatment combination for planting.

The plants in one crate were planted in the
greenhouse prior to the simulated shipping period.
Three other crates of bare-root plants were kept at the
long-term storage temperature (-2°C). These controls

were planted following 1, 2 and 3 week holding periods.

Experiment g

Six species of one year old, fall dug herbaceous
perennials including Achillea (Achillea filipendulina
’Coronation Gold’), Artemisia (Artemisia schmidtiana
’Silver Mound’), Phlox paniculata (Phlox paniculata
’Blue Boy’), Salvia (Salvia superba ’Blue Queen’) and
Sedum (Sedum spurium ’Dragon’s Blood’) were obtained
from Walters Gardens in Zeeland, Michigan on December
14, 1985 for use in this experiment.

The procedures used to process the plant material
was similar to that in Experiment 1 with the following
changes. In Experiment 2, each replicate contained 10
plants per species. Following 5 months of storage at

0°C, plant material was exposed to 0, 10, 20 or 30°C

(\1

1‘:
De
I‘e
ti

Ch.

f0]
FEE

Dot

26

for 1, 2 or 3 weeks to simulated a holding period prior
to marketing.

During both years, each root was inspected prior
to potting and was rated for mold coverage and
etiolation. Each plant was visually graded on the
following scale: 1-No observable mold; 2- up to 25%
coverage with molds; 3- 26-50% coverage; 4- 51-75%

coverage; and 5- 76-100% coverage.

Regrowth Analysis

As the bare-root plants were removed from the
treatments, they were planted with a peat-based,
soiless media in five inch clay pots. The greenhouse
was kept at a temperature of 10° C during the night and
21° C during the day. No supplemental lighting was
used and the plants were not fertilized during the 4
week regrowth period.

In the greenhouse, each plant was rated for
regrowth quality 4 weeks after planting. This time
period was determined to be an ideal time to evaluate
regrowth since treatment differences manifested at this

time were indicative of future growth and developmental
icharacteristics.

The rating was on a scale from 1 to 5 as
follows: 1- No regrowth observed; 2- up to 25% of the
regrowth potential expected; 3- 26-50% of the regrowth

potential: 4- 51-75% of the regrowth potential; and 5-

27

76-100% of the regrowth potential. Factors considered
in this subjective rating system included the number of
shoots, length of shoots and overall vigor of the new

growth.

Statistical Analysis

Experiment 1 - The analysis of variance was done
on a species by species basis. The three—way analysis
of variance consisted of 3 shipping temperatures x 4
holding temperatures x 3 holding periods with 6
replicates.

Experiment g - Shipping temperatures were not
tested so the two-way analysis of variance included 3
holding temperatures x 3 holding periods and was run on
a species by species basis. [Note: Data for week 3 at
30°C was not available so this temperature was not

included in the AOV.]

Results

Experiment 1

Aquilegia

Exposure of bare-root Aquilegia to a holding
temperature of 20°C for greater than one week reduced
the subsequent plant regrowth rating (Figure 1.1). No
significant differences in regrowth quality following
exposure to holding temperatures of -2, 5 and 10°C over
a 3 week period (Figure 1.1). Bare-root plants kept at
20°C for a three day simulated "shipping" period
exhibited a reduction in subsequent regrowth rating
independent of holding temperature or duration (Table
1.1). Overall, the regrowth quality of Aquilegia was
very high reflecting rapid shoot growth by the majority
of the treatment plants. The only exceptions were

those held 2 or 3 weeks at 20°C (Figure 1.1).

Artemisia

The 3-way interaction among shipping temperature,
holding temperature and holding time was significant at
the .008 level. Overall, regrowth ratings for this
species were very good with an average of 4.7 out of a

possible 5.0. Three weeks at 20°C following shipping

28

29

Figure 1.1. Relationship between the 4 week regrowth
rating of Aquilegia and length of exposure to
different holding temperatures averaged over 3
shipping temperatures.

Regrowth grades: 5 - 100% of regrowth potential; 4 -
75%; 3 - 50%; 2 - 25%; and 1 - No observable growth.

REGROWTH RATING

30

AQUILEGIA

 

 

 

 

“.3
I.
U)
C1
0
()1
ll

r—-1
0"

 

 

 

1 T I I
O I 2 3

HOLDING PERIOD
(Weeks)

31

 

Table 1.1. Mean 4 week regrowth ratingsy of Aquilegia
as influenced by 3 days at various shipping
temperatures and averaged over all holding
temperatures and holding period.

 

MeanRegrowth
Shipping Temperature

 

 

 

Rating
(°C)
5 4.5
10 4.7
20 4.1

 

LSD.05- 0.3

y: Regrowth grades: 5 - 100% of regrowth potential:
4- 75%; 3 - 50%: 2 - 25%; and 1 - No observable
growth.

32

temperatures of 5 and caused a decline in regrowth
quality for Artemisia (Figure 1.2). Plants held
continuously at 20°C through both the shipping and
holding periods did not decline significantly in 4 week
regrowth rating compared to other treatments. Regrowth
quality following holding times of 1, 2 or 3 weeks at -
2, 5 or 10°C showed no significant decline regardless

of shipping temperature (Figure 1.2).

Dicentra

Dicentra maintained an overall regrowth quality
average of 4.8 out of a possible 5.0 (Table 1.2). A
holding temperature of -2°C consistently resulted in a
statistically significant decline of 6% in regrowth
ratings compared to those plants held at 5, 10 and 20°C
in all other combinations. Neither shipping
temperatures nor weeks had a significant effect on

regrowth quality of Dicentra.

Asclepias

In contrast to other species tested, the regrowth
rating of Asclepias increased following three days at
10 and 20°C shipping temperatures and at one week in a
holding temperature of 20°C (Figure 1.3). The 3-way

interaction among shipping temperature, holding

33

Figure 1.2. Mean four week regrowth rating of
Artemisia following 3 days at different shipping
temperatures and 1 to 3 weeks at different holding
temperatures.

Regrowth grades: 5 - 100% of regrowth potential:
4 -75%; 3 - 50%; 2 - 25%; and 1 - No observable
growth.

REGROWTH RATING

R EGROWTH RATING

[:3

REGROWTH RADNG

34
ARTEMISIA

 

Shipping Tomponmn 50

 

LSD.OS =-

 

 

 

 

3 IO 17

24

 

Shipping Tanporom 1°C

LSD.OS -

 

 

 

 

3 IO 17

24

 

Shipping Tompmhn 2°C

 

LS0.0S =-

 

  

 

 

3 IO 1.7

HOLDING PEP-IOU
(Days)

1111

35

 

Table 1.2. Mean 4 week regrowth quality ratingy for
Dicentra as influenced by different holding
temperatures.

 

Regrowth Rating of Dicentra

Holding Regrowth

 

Temp. Rating
(00)
-2 4.5
5 4.9
10 4 9
22 4.8
Avg. 4.8

 

LSD.05 - 0.3

y: Regrowth grades: 5 - 100% of regrowth potential:
4 - 75%; 3 - 50%: 2 - 25%; and 1 - No observable
growth.

 

36

temperature and time was significant at the .000 level.
The results following exposure to other shipping and
holding temperatures were variable.

The mean survival percentage of Asclepias was
76.7% but was 90% for plants held at 20°C. No plants
survived following a shipping temperature of 5°C and
one week at -2°C (Figure 1.3b). When the 5°C shipping
temperature was followed by a holding temperature of
20°C, all plants survived in all three weeks (Figure
1.3b).

Phlox subulata

Shipping temperature did not significantly effect
the subsequent regrowth of Phlox subulata. The 2-way
interaction between holding temperature and weeks was
significant at the .000 level. Following 2 or 3 weeks
at a holding temperature of 20°C, there was a
significant decline in regrowth quality (Figure 1.5).
All plants died after 2 and 3 weeks at 20°C following a
shipping temperature of 20°C and after 3 weeks at 20°C
following shipping at 10°C. Holding temperatures of -2
and 5°C showed no decline in regrowth quality but there
was a significant decline after 3 weeks at 10°C (Figure

1.5).

Coreopsis
The 3-way interaction among shipping temperature,

holding temperature and time was significant at

37

Figure 1.3. Four week regrowth rating of Asclepias
following 3 days at different shipping temperatures
and 1 to 3 weeks at different holding temperatures.

Regrowth grades: 5 - 100% of regrowth potential;
4 - 75%; 3 - 50%; 2 - 25%; and 1 - No observable
growth.

REGROWTH RATING REGROWTH RADNG

REGROWTH RATING

38
ASCLEPIAS

 

Shipping Tompnmhn 50

LSD.05 I

 

 

 

 

Shipping Tempura" 1°C

...... \<

L

 

 

 

Shipping Tatum 200

 

LSD.05 :-

 

 

 

3 IO 17 24

HOLDING PERIOD
Days)

1111

10
20

39

Figure 1.4a. Four week regrowth rating of surviving
plants of Asclepias following 3 days at different
shipping temperatures and 1 to 3 weeks at different
holding temperatures.

Regrowth grades: 5 - 100% of regrowth potential;
4 - 75%: 3 - 50%; 2 - 25%: and 1 - No observable
growth.

Figure 1.4b. Percent survival of Asclepias following 3
days at different shipping temperatures and 1 to 3
weeks at different holding temperatures.

40

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A933
GOEum 925.51

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ON:

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9mm: Hmoaoaa

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41

the .001 level. Bare-root plants of Coreopsis held at
20°C had an average regrowth rating of only 1.9 out of
5.0 as averaged over all 3 weeks (Data not shown).
Coreopsis had an overall survival rate of 57.3%
and no plants survived 2 or 3 weeks at 20°C shipping
and holding temperatures (Figure 1.7). The survival
pattern of this species was erratic and the only
obvious trend was the observed loss in plant viability
after 2 and 3 weeks at 20°C. The regrowth ratings
of the surviving plants, however, were nearly all above
3.5 (Figure 1.6b). The exceptions were those plants
stored in the 20°C holding temperature for 3 weeks
following shipping at 5 and 10°C although 10°C was not

consistently detrimental. (Figure 1.6b).

92m

The overall average regrowth rating was very low
(2.0) and the ratings exhibited a high level of
variability throughout. No trends were noted in the
results (Data not shown). The 3-way interaction for
regrowth quality among shipping temperature, holding
temperature and time was significant at the .000 level.

Survival rate for Geum overall was 34.9% and this
data was also highly variable among treatments. No

clear trends could be delineated in the data or in

regrowth ratings of surviving plants which had an

42

Figure 1.5. Relationship between 4 week regrowth
rating and time in holding temperatures of Phlox
subulata averaged over the 3 shipping temperatures.

Regrowth grades: 5 - 100% of regrowth potential;
4 - 75%; 3 - 50%; 2 - 25%; and 1 - No observable
growth.

Regrowth Rating

43

PHLOX SUBULATA

 

 

 

LSD.05

 

10
on

by

 

H

o—o

e—o

H

K\

I E 3
HOLDING PERILID

We eke S)

 

44

Figure 1.6a. Four week regrowth rating of Coreopsis
following 3 days at different shipping temperatures
and 1 to 3 weeks at different holding temperatures.

Regrowth grades: 5 - 100% of regrowth potential;

4 - 75%: 3 - 50%; 2 - 25%; and 1 - No observable
growth.

Figure 1.6b. Four week regrowth rating of surviving
plants of Coreopsis following 3 days at different

shipping temperatures and 1 to 3 weeks at different
holding temperatures.

Regrowth grades: 5 - 100% of regrowth potential;

4 - 75%; 3 = 50%; 2 - 25%; and 1 - No observable
growth.

45

8E .... 02.0.51

933$

00.1 a 02.0.5:

00.1 n. 02.0.51

 

 

r3 6: -
swam fiuwuns)

V

fi—r t I
it)

 

 

 

 

 

 

 

  

8. 23.1....» 32......

-l") (a '—

é
ONILVU HMOUOBH

I0

 

 

mfimoumou

03938

ONILVB HIM

(

46

Figure 1.7. Percent survival of Coreopsis following 3
days at different shipping temperatures and 1 to 3
weeks at different holding temperatures.

1g3
33

PERCENT SURVIVAL

PERCENT SURVIVAL

ENT SURVIVAL

"
J

PER(

 

47

COREOPSIS

' Shipping Ternperoiue 5C
100« /A\
/

75- \ \

251

 

 

 

 

I Shipping Tampa-om 1°C

 

 

 

 

 

a—a -2
H 5
o—c 10
0 ~._ 1 H 20
3 10 H7 ‘24

HOLDING PERIOD
IDOyS;

avera
consi

other

spec:
not :
for :
shipj
cons
show
amon

time

48

average rating of 3.0. Even exposure to 20°C did not
consistently reduce regrowth quality compared to the

other temperatures (Data not shown).

Lavandula

Lavandula had an overall average regrowth rating
of only 2.0 and only 45% of the plants survived. The
data for regrowth ratings and survival rate for this
species exhibited a high degree of variability (Data
not shown). Exposure to the 20°C holding temperature
for 3 weeks resulted in 100% mortality after all
shipping temperatures, however, there were no
consistent detrimental effects at 10°C (Data not
shown). The 3-way interaction for regrowth quality
among shipping temperature, holding temperature and

time was significant at the .000 level.

cons
regr

was

the

am
ev
10
at
We
We

hi

49

Experiment 2

Achillea

The regrowth data for Achillea was displayed a
high degree of variability (Figure 1.8a). Regrowth
quality at 10 and 20°C declined after two weeks but
then increased after week 3. This effect, however, was
not so evident when only surviving plants were
considered (Figure 1.8b). The 2-way interaction for
regrowth quality between holding temperature and weeks
was significant at the .000 level.

Nearly one-third of the plants did not survive
(Data not shown). All plants were dead after 2 weeks at

the holding temperature of 30° (Figure 1.8).

Phlox paniculata

Overall, this species did very well with an
average regrowth rating of 4.3. There were no problems
evident at holding or shipping temperatures of 0 and
10°C. Ratings declined significantly following 2 weeks
at 20°C but returned to high levels after the third
week. At 30°C, the regrowth ratings decline after 2
weeks (Figure 1.9). The 2-way interaction between
holding temperature and weeks was significant at

the .005 level.

50

Figure 1.8a. Relationship between 4 week regrowth
rating and time in holding temperatures for Achillea.

Regrowth grades: 5 - 100% of regrowth potential;
4 - 75%; 3 - 50%; 2 - 25%; and 1 - No observable
growth.

Figure 1.8b. Relationship between 4 week regrowth
rating of surviving only and time in holding
temperatures for Achillea.

Regrowth grades: 5 - 100% of regrowth potential;
4 - 75%; 3 - 50%: 2 - 25%; and 1 - No observable
growth.

51

ID

 

 

 

 

02:39. ngomowm

 

ERIOD

Weeks)

HOLD(ING F’

 

 

 

 

 

d —

3 64

”wflcoi 052233
2.5.x Igomoma

O

HOLDING PERIOD
(Weeks)

52

Figure 1.9a. Relationship between 4 week regrowth
rating and time in holding temperatures of for
Phlox paniculata.

Regrowth grades: 5 - 100% of regrowth potential;
4 - 75%; 3 - 50%; 2 - 25%; and 1 - No observable
growth.

Figure 1.9b. Relationship between 4 week regrowth
rating of surviving only and time in holding
temperatures for Phlox paniculata.

Regrowth grades: 5 - 100% of regrowth potential;
4 - 75%; 3 - 50%: 2 - 25%; and 1 - No observable
growth.

REGROWTH RATING

RATING

Surviving Plants]

REGROWTH

I

N
1
O

53

PHLOX PANICUIATA

 

  

A

 

  

 

 

 

 

LSD.05 - H 0
H 10
0—0 20
1 r I H 3
o 1 2 3'
HOLDING PERIOD
(Weeks)
A

 

A

(A
l

1 O
20
30

 

 

IIII

 

o i i 3'
HOLDING PERIOD
(Weeks)

I'n

regTO‘
(LSD.
signi

were

temp

leve

Sig:
ave:

The

54

Sedum

Overall, Sedum did very well with an average
regrowth rating of 4.1 and a range of 3.4 to 4.7
(LSD.05-1.0). Even 2 weeks at 30°C did not cause
significant problems. No trends in treatment response
were obvious in the data although some slight
statistical differences occurred after the first week
(Figure 1.7). The 2-way interaction between holding
temperature and weeks was significant at the .027

level.

Artemisia

The regrowth ratings for Artemisia declined
significantly over the three weeks in storage when
averaged over all holding temperatures (Table 1.3).
The results for holding temperature were also
significant, with 10°C resulting in a significantly
higher average regrowth rating than either 0 or 20°C
(Table 1.4). The 2-way interaction was not

significant.

55

Figure 1.10a. Relationship between 4 week regrowth
rating and time in holding temperatures for Sedum.

Regrowth grades: 5 - 100% of regrowth potential;
4 - 75%; 3 - 50%; 2 - 25%; and 1 - No observable
growth.

Figure 1.10b. Relationship between 4 week regrowth
rating of surviving plants only and time in holding
temperatures for Sedum.

Regrowth grades: 5 - 100% of regrowth potential;
4 - 75%; 3 - 50%: 2 - 25%; and 1 - No observable
growth.

REGROWTH RATING

REGROWTH RATIN
[Surviving Plants

56

SEDUM

 

 

 

 

 

 

IIIII

 

 

 

 

 

IIII

 

 

2‘ LSD.05 '
1 . . .
O I 2 3
HOLDING PERIOD
(Weeks)
5.
A:
4- fl
3..
2..
I r I .
O I 2 3

HOLDING PERIOD
(Weeks)

Tab

aamz

57

 

Table 1.3. Mean 4 week regrowth ratingsy of Artemisia
as influenced by 1 to 3 weeks post-storage duration
averaged over shipping and holding temperatures. The
main effect was significant at the .000 level and the
2-way interaction was not significant.

 

Holding Regrowth

 

Period Rating
(Weeks)
1 4.6
2 3.7
3 3.3

 

LSD.05 - 0.2

 

y: Regrowth grades: 5 - 100% of regrowth potential;
4- 75%; 3 - 50%; 2 - 25%; and 1 - No observable
growth.

 

58

 

Table 1.4. Mean 4 week regrowth ratingsy of Artemisia
as averaged over weeks and shipping temperatures. The
main effect was significant at the .000 level and the
2-way interaction was not significant.

 

 

Holding Regrowth
Temperature Rating
(°C)
0 3.5
10 4.4
20 3.7

 

LSD.05 - 0.2

 

y: Regrowth grades: 5 - 100% of regrowth potential;
4- 75%; 3 - 50%; 2 - 25%; and 1 - No observable
growth.

 

_s_g

53
only 2.
for the
Rgnif
{Table
result
signii
tempe

was II

59

Salvia

Salvia had an average overall regrowth rating of
only 2.4 and a survival rate of 64%. Regrowth ratings
for the third week of holding prior to planting were
significantly lower than those in the first two weeks
(Table 1.5). The 20°C holding temperature, which
resulted in an overall mean rating of only 1.9, was
significantly lower than the other treatment
temperatures tested (Table 1.6). The 2-way interaction

was not significant.

60

 

Table 1.5. Mean 4 week regrowth ratingsy of Salvia as
influenced by time over 0, 10 and 20 C holding
temperatures. The main effect was significant at the
.041 level and the interaction was not significant.

 

Holding Regrowth

 

Period Rating
(Weeks)
1 2.9
2 2.4
3 2.1

 

LSD.05 - 0.6

y: Regrowth grades: 5 - 100% of regrowth potential;

4- 75%; 3 - 50%; 2 - 25%; and 1 - No observable
growth.

 

 

Table 1.6. Mean 4 week regrowth ratingsy of Salvia as
influenced by temperatures averaged over 1, 2 and 3
weeks in holding. The main effect was significant at
the .013 level and the interaction was not significant.

 

 

 

Holding Regrowth
Temperature Rating
(°C)
0 2.6
10 2.8
20 1.9
LSD.05 - 0.6

y: Regrowth grades: 5 - 100% of regrowth potential;
4- 75%; 3 - 50%; 2 - 25%; and 1 - No observable
growth.

 

evider
root I
etiol:
1.7 a
shove
ITabl
in tr
grovi
ship]

and

temp
inCr
inCI

POQ'

an
DeI
th.

in

61

Etiolation

Prior to potting, each bare-root was examined for
evidence of etiolated growth. Over 72% of the bare—
root Achillea, Aquilegia and Phlox paniculata exhibited
etiolated growth of 2.5 to 5 cm in length (see Table
1.7 and 1.10). Artemisia, Salvia, Sedum and Lavandula
showed little or no etiolated growth prior to potting
(Tables 1.7 and 1.9). Generally, there was an increase
in the percentage of bare-root plants with etiolated
growth as the temperature increased in both the
shipping and holding phases of Experiment 1 (Tables 1.7
and 1.8).

Following 3 days in the different shipping
temperatures, Asclepias and Coreopsis showed an
increase in etiolation percentage as temperatures
increased. At 10 and 20°C, all or nearly all the bare-
roots of Aquilegia showed signs of etiolated growth
(Table 1.7).

Over the 4 holding temperatures, Coreopsis showed
a definite trend toward an increase in etiolation with
an increase in temperature while Aquilegia had a high
percentage of etiolated bare-root plants throughout all
the holding temperatures. Geum and Dicentra showed an
increase in etiolation as temperatures increased from -

2 to 10°C but then declined after 20°C (Table 1.8).

62

 

Table 1.7. Mean percentage of bare-root plants
exhibiting etiolated growth upon visual inspection
prior to potting as effected by shipping
temperatures during Experiment 1.

 

Plants Exhibiting Etiolated Growth (%)

 

Shipping Temperature
(°C)
2 12 .22
SPECIES:
Aquilegia 65.3 100.0 95.8
Artemisia 0.0 0.0 8.3
Asclepias 5.6 11.0 25.0
Coreopsis 19.5 38.9 69.4
Dicentra 52.7 45.8 54.1
Geum 22.2 18.0 29.1
Lavandula 0.0 0.0 0.0
Phlox sub. 19.4 5. 13.8
AVG. 23.1 27.4 36.9

 

 

Table 1.8. Mean percentage of bare—root plants
exhibiting etiolated growth upon visual inspection
prior to potting as affected by holding
temperatures during Experiment 1.

 

Plants Exhibiting Etiolated Growth (%)

Holding Temperatures

 

(°C)
-_2. E _1_0 fl
SPECIES:

Aquilegia 72.2 83.3 96.3 96.3
Artemisia 0.0 0.0 11.1 0.0
Asclepias 0.0 0.0 14.8 40.8
Coreopsis 22.2 35.2 51.9 61.1
Dicentra 27.8 50.0 77.8 48.1
Geum 5.6 31.6 37.0 18.6
Lavandula 0.0 0.0 0 0 0.0
Phlox sub. 3.7 0.0 9.2 38.9
AVG. 16.4 25.0 37.3 38.0

 

63

 

Table 1.9. Mean percentage of bare—roots exhibiting
etiolated growth upon visual inspection prior to
potting as affected by weeks in holding temperatures
during Experiment 1.

 

Plants Exhibiting Etiolated Growth (%)

Duration of Holding Period

 

 

(Weeks)
1 g 3 AVG.
SPECIES:

Aquilegia 76.4 91.7 93.1 87.0
Artemisia 8.3 0.0 0.0 2.8
Asclepias 0.0 8.3 33.3 13.9
Coreopsis 40.3 48.6 39.0 42.6
Dicentra 41.7 62.5 48.6 50.9
Geum 22.3 25.0 22.3 23.2
Lavandula 0.0 0.0 0.0 0.0
Phlox sub. 0.0 31.9 6.9 12.9
Avg. 23.6 33.5 30.4 29.2

 

 

Table 1.10. Mean percentage of bare-roots exhibiting
etiolated growth upon visual inspection prior to
potting as effected by weeks in storage during
Experiment 2.

 

Plants Exhibiting Etiolated Growth (%)

Duration of Holding Period

(Weeks)
i a 2
SPECIES:
Achillea 87.5 75.0 87.0
Artemisia 2.5 12.5 20.0
Phlox paniculata 60.0 70.0 100.0
Salvia 0.0 0.0 0.0
Sedum 0.0 0.0 0.0
AVG. 30.0 31.5 41.4

 

64

Table 1.11. Mean percentage of bare-roots exhibiting
etiolated growth upon visual inspection prior to
potting as effected by holding temperatures during
Experiment 2.

 

Plants Exhibiting Etiolated Growth (%)

Holding Temperatures

(°C)
2 a a). 22.
SPECIES:
Achillea 63.3 73.3 100.0 100.0
Artemisia 0.0 10.0 16.7 20.0
Phlox paniculata 46.7 93.3 83.3 75.0
Salvia 0.0 0.0 0.0 0.0
Sedum 0.0 0.0 0.0 0.0
AVG. 22.1 35.3 37.3 35.3

 

Mold Ratings

Each bare-root plant was visually inspected prior
to potting and was given a rating based upon the
percentage of the surface area covered by molds. All
species in both experiments had a mean rating of less
than 2.0, i.e. 1-25% coverage by molds, except
Coreopsis, Lavandula and Geum which had averages of
2.9, 2.4 and 2.3, respectively.

There were no obvious effects of the treatments
on the amount of mold coverage with the exception of
Phlox subulata which tended to have increased levels of
mold in 5, 10 and 20°C as compared to -2° (results not
shown). In addition, no correlation could be made
between the presence of mold coverage and the 4 week
regrowth rating of the bare-root plants (results not

shown).

Discussion

Following long-term storage, bare-root
herbaceous perennials are often subjected to elevated
temperatures during shipment and again as they await
potting or delivery to the retail markets. Based on
typical responses of many horticultural crops to high
temperatures following harvest, it would seem likely
that exposure to non-refrigerated conditions for
extended periods would cause a decline in regrowth
quality or survival of bare-root plants.

In the experiments reported here, which were
conducted over a 2 year period, 12 species of bare-root
herbaceous perennials were remarkably tolerant of post—
storage exposure to elevated temperatures. It should
be noted that the 12 species used are considered to be
average to poor in their ability to survive storage
(Wayside Gardens, personal communications).

Post—storage exposure to 20°C for 2 and/or 3
weeks caused a significant decline in regrowth quality
for only 4 of the 12 species tested (Table 1.12). One
of these, Salvia, showed a negative response to all
temperatures including 0°C. No species showed a
significant decline in regrowth after 1 week at 20°C or
up to 3 weeks at 10°C. In fact, all species survived
one week at 30°C although 3 of the 5 species tested had
a moderate decline in regrowth quality (Table 1.13).
Sedum did well following 2 weeks at 30° and Phlox

65

66

paniculata had only a moderate decline in regrowth
quality. Three of the 5 species exposed to 30°C for 2
weeks did experience an extreme decline in regrowth
quality.

Asclepias actually appeared to show some positive
effects from a brief exposure to elevated temperatures
following long-term storage. This plant is known as a
late emerging species in the garden (39) which may
indicate a need for exposure to elevated soil
temperatures before it resumes active growth in the
spring. A third experiment had been designed to test
this response under a wider range of temperatures.
Unfortunately, the bare-root plants to be used molded
severely during storage and failed to survive. Further
study of this phenomenon might prove valuable in

defining proper post-storage handling for this species.

67

 

Table 1.12. Relative sensitivity of herbaceous

perennials to exposure to holding temperatures
of 10 and 20°C for 2-3 weeksX based on regrowth
quality following storage.

 

 

Degree of Holding Temperature
Impact o_n Regrowth 1329 2_o£_g
Slight or None Achillea Aquilegia“
Aquilegia“ Dicentra“
Artemisia Phlox pan.
Asclepias Sedum
Coreopsis“
Dicentra

Phlox paniculata
Phlox subulata

 

 

 

Sedum
Moderate. Artemisia
Extreme Salvia Achillea
Coreopsis“
Phlox sub“
Salvia+
Inconsistent and/or Geum“ Asclepias“
Inconclusive Lavandula Geum
Lavandula

 

There was no effect following one week at these
temperatures in most cases.

Species sensitive to promotion of etiolated growth
at elevated temperatures.

Species responded negatively to all temperatures
over time.

 

68

 

Table 1.13. Relative sensitivity of herbaceous
perennials to exposure to holding temperatures of
30°C for 1-2 weeks based on regrowth following
storage.

 

 

 

Degree of Weeks
Impact 1 g
Slight or None Phlox paniculata
Sedum Sedum
Moderate Achillea Phlox pan.
Artemisia
Salvia
Extreme Achillea
Artemisia
Salvia

 

Extreme - Overall average rating of 1-2;
Moderate -2-3; Slight or None - 3-5.

 

Geum, Coreopsis and Lavandula exhibited variable
responses to the treatments with regrowth ratings
failing to show any definite trends due in part to
erratic plant survival rates. Coreopsis generally
achieved a good regrowth rating in almost all cases
where growth occurred but its main problem was in
surviving the storage treatment. All 3 of these
species are considered difficult-to—store and are
frequently the subject of consumer complaints (Wayside
Gardens, Inc. and Walters Gardens, Inc. personal
communications). These species also require additional

study to define the factors responsible for their

69

unreliability as stored bare-root herbaceous
perennials.

In Experiment 1, there was an attempt made to test
the effect of a simulated shipping temperature over a 3
day period. Artemisia, Coreopsis, Dicentra and Phlox
subulata were not significantly effected by shipping
temperatures. Significant negative effects of the
three day shipping period were found for Aquilegia at
20°C, Asclepias at 5°C, Geum at both 5 and 20°C, and
Lavandula at both 10 and 20°C. No single, clear trend
could be delineated. This factor was not tested the
second year because of this lack of an apparent trend
during the holding period and since even 1 week at 10
or 20°C did not cause a significant decline in regrowth
quality for any of the species.

Maqbool (28) found that storage temperatures of
2°C or higher tended to encourage etiolated growth on
stored bare-root herbaceous perennials. In Experiment
1, the percentage of bare-root plants which exhibited
etiolated growth after post-storage holding tended to
increase as the shipping temperature increased.
However, there did not appear to be a direct
correlation between the presence of etiolated growth
and subsequent regrowth quality. For instance, over
72% of the Aquilegia plants had etiolated growth prior
to potting but they maintained an overall regrowth

rating of 4.3 of a possible 5.0.

70

It should be noted that the experimental plants
were planted in potting media, watered regularly and
grown in a climate controlled greenhouse set for cool
daytime temperatures. If the tender, etiolated growth
found on these bare-root plants were subjected to
harsher conditions often encountered in the garden, the
results may be less favorable.

The objective of this study was to determine the
impact of elevated post-storage temperatures on the
regrowth quality of bare-root herbaceous perennials.
Therefore, efforts were made to minimize other
potential stresses such as desiccation by storing all
plants inside bulk-packed polyethylene bags. The bags
were loosely sealed to facilitate the exchange of
oxygen and carbon dioxide while minimizing moisture
loss. Also, the plants were not tightly packed into
the crates which allows for air circulation and the
avoidance of heat build-up.

The practical implications of these results are
that bare-root herbaceous perennials which are wrapped
properly to avoid desiccation and to allow gas and heat
exchange, can withstand at least temporary exposures to
elevated temperatures. Generally, most bare—root
herbaceous perennials should be able to withstand as
much as 2 to 3 weeks at 10°C or one week at 20°C

without significant loss of regrowth quality. Some

71

species, especially those generally considered easy-to—
store, may even withstand prolonged periods at 20°.
Storage at these elevated temperatures certainly
cannot be generally advocated but, if unavoidable
conditions force such exposure, the probability is good

that most of the plants will survive.

CHAPTER 11

Influence 31 Successive Freeze/Thaw Cycles
9g Regrowth Performance 21 Bare-Root

Herbaceous Perennials

72

Introduction

Herbaceous perennials are often field—grown,
harvested in the fall as bare-roots and stored for
varying periods of time by commercial growers. As
orders are processed, the bare-root plants are removed
from storage and shipped to the retail outlet where
they are either held for future delivery or potted for
sale. It is recommended that most bare-root
herbaceous perennials be stored at a constant
temperature in the range of 0 to -2°C (26)(28). At
times, mechanical malfunctions in refrigeration systems
or temporary interruptions in storage during shipping
and handling may allow temperatures to fluctuate.
Frozen bare—roots may temporarily thaw when
temperatures rise and unfrozen material may freeze if
temperatures drop too low.

At present there is no published information
available to help growers and retailers identify those
species which will not tolerate such fluctuations. This
experiment was designed to test the effects of
successive cycles of temperatures of -3°C and 1°C on 6
bare-root herbaceous perennial species which had been
been packaged and stored. Plant response was monitored
by evaluating subsequent regrowth potential following

exposure to one or more cycles.

73

Materials and Methods

Six species of one year old herbaceous perennials
of were used: Coreopsis (Coreopsis gpandiflora
’Sunray’),Geum (figgm chiloense ’Lady
Strathden’),Hemerocallis (Hemerocallis fulva ’Tawny’),
Hosta (Hosta ’Honeybells’), Lupine (Lupinus ’Russell
Hybrids’) and Monarda (Monarda didyma ’Croftway Pink’).
The plant material was taken directly from processing
at Walters Gardens in Zeeland, Michigan on November 8,
1984, to the campus in East Lansing. Five plants of
each of the 6 species were placed into a 4 mil
polyethylene bag. Each bag represented one replicate
and two bags were placed inside a wooden celery crate
prior to storage. The bags were folded over but not
completely sealed.

The crates were placed in a controlled environment
storage room at 1°C for one week followed by a week at
-3°C in a second room. Following exposure to the
subzero temperature, the crates were shifted back to
the 1°C room to start another cycle. Thermocouples were
placed in the crates during the exposure to -3°C to
determine the rate of equilibration with the
surrounding air temperature. After one day to allow the
plants to thaw, one crate of plants was removed for
potting and regrowth analysis in the greenhouse. Six

cycles were completed during the experiment.

74

75

The plants in the greenhouse were evaluated each
week for 4 weeks following planting and were rated
individually for regrowth quality. The rating was on a
scale of 1 to 5 as follows: 1- No regrowth observed; 2—
up to 25% of the regrowth potential expected after 4
weeks in the greenhouse; 3- 26-50% of the regrowth
potential; 4- 51-75% of the regrowth potential: 5—76-
100% of the regrowth potential.

Factors considered in this subjective rating
system included the number of shoots, length of shoots
and overall growth rate. After observing the different
growth rates attained by varieties used in this and
other experiments (Klobucher and Cameron, unpublished),
it was determined that the 4 week rating was most
indicative of a plant’s regrowth potential.

The data were analyzed as a completely randomized,

1-way design with 2 replicates and 5 observations per

replicate.

Results

All plants of Hemerocallis, Hosta and Monarda
survived each of the 6 freeze/thaw cycles and Lupine
was only slightly affected, losing one plant in each of
the final 3 cycles (Figure 2.2).

Hemerocallis, Hosta, Lupine and Monarda had very
high regrowth ratings throughout the experiment with
overall averages of 4.0 or greater (Figure 2.1).
Monarda’s regrowth ratings were, however, somewhat
variable but generally improved over the 6 cycles.

Lupine attained a high regrowth rating following
each of the first 3 cycles before experiencing a slight
but statistically significant decline after each of the
final 3 cycles (Figure 2.1) Much of the decline could
be attributed to the death of 10% of the plants during
that period since the surviving plants continued to
achieve a very high rating (data not shown).

Following the first cycle, only one of the bare-
root Coreopsis plants died while all of the Geum
survived (Figure 2.2). After subsequent cycles, the
survival rates for these two species were somewhat
variable, however. The trend was for a decline in
survival as the number of cycles increased. Overall,
only 55% of the Coreopsis and 36.7% of the Geum
survived six freeze/thaw cycles (data not shown).

When considering only those plants which survived,
Geum maintained an average regrowth rating of 3.9. The

76

77

surviving plants of Coreopsis maintained an average
rating of 4.9 after the first 4 cycles but then
declined to 2.8 and 2.0 respectively during the final

two cycles (Table 2.1).

 

Table 2.1. Mean 4 week regrowth ratingsy of surviving
Coreopsis and Geum as influenced by storage in
alternating temperature cycles consisting of one
week at 1°C and one week at -3°C.

 

REGROWTH RATINGS

 

CYCLES
SPECIES: 1 g g 1 g g
COREOPSIS 5.0 4.8 4.8 5.0 2.8 2.0
GEUM 4.0 4.0 -—- 3.5 4.0 4.0

 

y: Regrowth grades: 5 - 100% of regrowth potential;
4- 75%: 3 - 50%; 2 - 25%: and 1 - No observable
growth.

 

The regrowth ratings for Coreopsis were variable
but generally, declined over time. After each of the
final two cycles, the ratings dropped to very low
levels of 1.7 and 1.1 respectively (Figure 2.1).

The regrowth rating of the Geum was high (4.0)
following the first cycle but declined significantly
over the following cycles with an overall average of
only 2.1 (Figure 2.1). All plants died after the third

cycle (Figure 2.2).

78

Figure 2.1. Effect of exposure to freeze/thaw cycles
(1°C for one week; -3°C for one week) during storage
on the 4 week mean regrowth ratingsy of Coreopsis,
Geum, Hemerocallis, Hosta, Lupine and Monarda.

Regrowth grades: 5 - 100% of regrowth potential;
4 -75%: 3 - 50%; 2 - 25%; and 1 - No observable
growth.

REGROWTH RATING REGROWTH RATING

REGROWTH RATING

79

 

 

 

 

 

 

 

 

 

5‘ COREOPSIS GEUM
\.
4-4 f\ 1‘
/ \ \
3‘ i \\
\
2‘ . \\ A
m a .I \ \/‘
1 - v v “I.” -I \
HEM EROGALLIS HOSTA ‘—

 

 

iflv

 

 

...-1

 

 

 

 

MONARDA

. ‘M
/

 

 

 

‘4
a I
21
Ln.”‘1 ts..°§ .1
1 . . . . - . . T L ,
‘I 2 3 4 5 6 ‘I 2 3 4 5 6

FREEZE/"HAW CYCLES

FREEZE/"THAVI’ CYCLES

80

Figure 2.2 Effect of exposure to Freeze/Thaw Cycles
(1°C for one week; -3°C for one week) on the mean
regrowth ratingsy and percent survival of Coreopsis,
Geum, Hemerocallis, Hosta, Lupine and Monarda.

Regrowth grades: 5 - 100% of regrowth potential;
4 -75%; 3 - 50%; 2 - 25%; and 1 - No observable
growth.

81

Regrowth Rating (Bl—i!)

mmvmwp

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wmvnmp

28880

3.96 zaz<m~mo¢
m m e n N m n v n w—

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{Mg/Ling lanJad

(udwe we)

Discussion

The control of desiccation during the storage
period has been shown to be a the primary factor in
storage success (28), however, the maintenance of a
steady temperature level in the storage environment is
also of great importance (26)(28). In the garden, a
natural phenomenon referred to as a "mid-winter thaw"
occurs when winter temperatures rise and allow the soil
to thaw into the root zone for a brief period before a
return to subfreezing temperatures. A similar
situation occurs for stored bare-root plants when they
are moved from one storage area to another or when
temperature levels are allowed to fluctuate in the
refrigeration unit.

According to Levitt (21), most plant tissues
freeze at temperatures in the range of -1 to —2°C.
However, no evidence was gathered in this experiment to
confirm that the tissue froze during the exposure to
the —3°C storage temperature. Free water within the
polyethylene bag was observed to have frozen during the
week in -3°C.

Mader and Feldman (24) found that alternate
freezing and thawing of strawberry runners resulted in
a condition termed "physiological exhaustion". They
exposed strawberry runners to temperatures alternating
between 3 and -3°C. Following 24 days, roots of plants
treated in this manner had 9% less starch while the

82

83

tops had 15% less total sugars as compared to plants
held at a constant 3°C. Also, 50% of the plants
exposed to alternating temperatures died during
greenhouse regrowth but only 10% of the plants stored
at 3°C failed to survive. Seventy percent of plants
from the constant temperature were described as
"vigorous" compared to 10% of the plants from the
alternating group.

Alternating freezing and thawing temperatures did
not negatively effect all species tested in this
experiment. In fact, Hemerocallis, Hosta, Lupine and
Monarda showed little if any decline in regrowth rating
or survival following such treatments. The results for
Coreopsis and Geum were variable although the trend was
for a decline in both survival and regrowth rating.
When considering only those plants which survived,
Coreopsis showed a trend toward a declining regrowth
rate as the number of cycles increased and the
surviving plants of Geum maintained an acceptable level
of regrowth quality (data not shown).

The practical implications of the results of this
experiment are that some species of bare-root
herbaceous perennials appear to be able to withstand
exposure to variable temperatures with little effect on
either survival or regrowth quality. Other species,

however, may be effected but the response may be highly

84

variable due to an interaction or influence of other
environmental or physiological factors.

Coreopsis and Geum are generally considered to be
difficult-to-store under even ideal conditions (Wayside
Gardens and Walters Gardens, personal communications).
However, they would usually be expected to survive 12
weeks of storage as in this experiment if they are not
stressed by alternating temperatures. Ultimately, more
research is needed to determine if exposure to
alternating periods of freezing and non-freezing
temperatures is a problem for other bare-root

herbaceous perennials.

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88

39. Still, S. 1982. Herbaceous Ornamental Plants.
2nd Ed. Stipes Publishing Co., Champaign, ILL. p.25

40. Stuart, N.W. 1954. Moisture content of packing
medium, temperature and duration of storage as factors
in forcing lily bulbs. Am. Soc. Hort. Sci. 488-494.

41. Stuart, N.W., C.J. Gould and D.L. Gill. 1955.
Effect of temperature and other storage conditions on
forcing behavior of Easter lilies, bulbous iris and
tulips. 173-187.

42. Thomas, W.D. and Lazenby, A. 1968. Growth
cabinet studies into cold-tolerance of Festuca
arundinacea populations. II. Response to pretreatment
conditioning and to number and deviation of low
temperature periods. J. Agr. Sci. 30:347-353

43. Tomkins, R.G. 1962. The conditions produced in
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Bact. 25(2): 290-307.

44. Truter, A.B. and C.W. J. Bester. 1982.
Packing and cooling of strawberry runner plants.
Deciduous Fruit Grower. 32(11):485-489.

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Agriculture. Marketing Research Report. No. 196 pp.
32.

46. Worthington, J.T. and D.H. Scott. 1957.
Strawberry plant storage using polyethylene liners.
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of root trimming and storage containers on field
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Refrigeration 6(2):97—99.

Experiment 1

APPENDIX
Table 1.9

Analysis of Variance

 

 

 

 

 

 

89

Aquilegia
Deg. of Sum of Mean F
Source Freedom Squares Sgpare Value
Ship Temp. 2 13.0 6.5 7.83
Hold Temp. 3 31.2 10.4 12.52
HT x ST 6 7.9 1.3 1.59
Weeks 2 14.0 7.0 8.48
HT x WKS 6 23.6 3.9 4.74
ST x WKS 4 7.4 1.9 2.23
HT x ST x WK 12 14.8 1.2 1.49
ERROR 180 149.5 0.8
Artemisia
Deg. of Sum of Mean F
Source Freedom Squares Square Value
Ship Temp. 2 1.2 0.6 0.94
Hold Temp. 3 16.9 5.6 9.23
HT x ST 6 5.1 0.9 1.40
Weeks 2 9.8 4.9 8.07
HT x WKS 6 13.9 2.3 3.79
ST x WKS 4 1.7 0.4 0.71
HT x ST x WK 12 17.0 1.4 2.32
ERROR 180 109.8 0.6
Asclepias
Deg. of Sum of Mean F
Source Freedom Squares Sguare Value
Ship Temp. 2 41.7 13.9 9.19
Hold Temp. 3 36.6 18.3 12.08
HT x ST 6 41.8 7.0 4.60
Weeks 2 42.5 21.3 14.04
HT x WKS 6 25.3 4.2 2.78
ST x WKS 4 43.2 10.8 7.13
HT x ST x WK 12 66.2 5.5 3.63
ERROR 180 272.7 1.5

Prob.

0.000
0.000
0.148
0.000
0.000
0.065
0.124

Prob.

W

0.000
0.213
0.000
0.001
0.999
0.008

0.000
0.000
0.000
0.000
0.012
0.000
0.000

LSD.05
0.3

0‘93“

0.
O.
00

LSD.05

Prob. LSD.05

Coreopsis

 

 

 

 

 

 

Deg. of Sum of Mean F
Source Freedom Squares Sguare Value Prob.
Ship Temp. 2 101.4 33.8 13.66 0.000
Hold Temp. 3 2.9 1.4 0.58 0.999
HT x ST 6 9.2 1.5 0.62 0.999
Weeks 2 31.0 15.5 6.26 0.002
HT x WKS 6 57.4 9.6 3.87 0.001
ST x WKS 4 21.2 5.3 2.14 0.075
HT x ST x WK 12 82.9 6.9 2.79 0.001
ERROR 180 445.3 2.5

Dicentra

Deg. of Sum of Mean F
Source Freedom Squares Square Value Prob.
Ship Temp. 2 8.0 2.7 4.09 0.007
Hold Temp. 3 1.0 0.5 0.76 0.999
HT x ST 6 6.9 1.1 1.74 0.110
Weeks 2 3.4 1.7 2.63 0.073
HT x WKS 6 2.7 0.5 0.70 0.999
ST x WKS 4 1.9 0.5 0.72 0.999
HT x ST x WK 12 9.4 0.8 1.19 0.281
ERROR 180 118.0 0.7

Geum

Deg. of Sum of Mean F
Source Freedom Squares Sguare Value Prob.
Ship Temp. 2 42.0 14.0 8.73 0.000
Hold Temp. 3 22.5 11.2 6.98 0.001
HT x ST 6 29.3 4.9 3.04 0.007
Weeks 2 17.1 8.5 5.31 0.005
HT x WKS 6 19.9 3.3 2.07 0.057
ST x WKS 4 8.3 2.1 1.30 0.271
HT x ST x WK 12 104.2 8.7 5.40 0.000
ERROR 180 289.5 1.6

LSD.O

HCDHCDHCDO
moomomom

LSD.05

0099690

01010103010303

LSD.05

puma-00001

HODOOOD

Lavandula

 

Deg. of
Source Freedom
Ship Temp. 2
Hold Temp. 3
HT x ST 6
Weeks 2
HT x WKS 6
ST x WKS 4
HT x ST x WK 12
ERROR 180

Deg. of
Source Freedom
Ship Temp. 2
Hold Temp. 3
HT x ST 6
Weeks 2
HT x WKS 6
ST x WKS 4

HT x ST x WK 12
ERROR . 180

Sum of Mean
Squares Square
21.8 10.9
29.1 9.7
36.4 6.1
5.6 2.8
53.2 8.9
10.3 2.6
62.6 5.2
235.0 1.3

Phlox subulata

 

Sum of Mean
Squares Square
1.1 0.5
186.1 62.0
9.0 1.5
60.8 30.4
77.2 12.9
5.0 1.2
11.1 0.9
137.7 0.8

F

Value

8.34
7.43
4.65
2.13
6.79
1.97
4.00

Value

0.71
81.11
1.96
39.70
16.82
1.63
1.21

Prob.

0.000
0.000
0.000
0.120
0.000
0.098
0.000

Prob.

0.999
0.000
0.071
0.000
0.000
0.166
0.271

LL

LSD.0

HDODODO
w-amw>m#>pcn

o o o o

OUIO‘CDO‘ODCOUI

HODCOOO

HOLDING TIME

HOLDING TIME

HOLDING TIME

92

Experiment 2

Analysis of Variance

 

HOLDING TEMPERATURE 2 8.01 5.12
HOLDING TIME

 

HOLDING TEMPERATURE 2 6.93 4.76
HOLDING TIME

Achillea
DEG. OF MEAN F
FREEDOM SQUARE VALUE
2 16.94 10.83
TEMPERATURE 4 9.53 6.09
81 1.56
Artemisia
DEG. OF MEAN F
FREEDOM SQUARE VALUE
2 12.03 8.26
TIME X TEMPERATURE 4 2.12 1.45

81 1.46

Phlox paniculata

DEG. OF MEAN F
FREEDOM SQUARE VALUE
HOLDING TEMPERATURE 2 1.01 1.54
2 0.21 0.32
TIME X TEMPERATURE 4 2.58 3.92
81 0.66
Salvia
DEG. OF MEAN F
FREEDOM SQUARE VALUE
HOLDING TEMPERATURE 2 6.70 4.54
2 4.90 3.32
TIME X TEMPERATURE 4 2.35 1.59
81 1.48
Sedum
DEG. OF MEAN F
FREEDOM SQUARE VALUE
HOLDING TEMPERATURE 2 2.50 2.23
2 0.70 0.62
TIME X TEMPERATURE 4 3.25 2.89

81 1.12

PROB. LSD.05

0.008
0.000
0.000

O
0
1

.7
7

PROB. LSD.05
0.2
0.2

0.011
0.000
0.224

0.221
0.999
0.005

0.013
0.041
0.184

PROB. LSD.05

0.114
0.999
0.027

0.

7

PROB. LSD.05

0.6
0.6

1

PROB. LSD.05

1.

0

Source
Total
Treatment
Error

Source
Total

Treatment-

Error

Source
Total
Treatment
Error

Source
Total
Treatment
Error

Source
Total
Treatment
Error

Source
Total
Treatment
Error

93

Freeze/Thaw Experiments

Coreopsis

 

 

 

 

 

 

 

 

 

Deg. of Sum of Mean F
Freedom Squares Square Value
59 213.4
5 95.8 19.2 8.73
54 117.6 2.2
Geum
Deg. of Sum of Mean F
Freedom Squares Sguare Value
59 142.8
5 59.7 11.9 7.73
54 83.1 1.5
Hemerocallis
Deg. of Sum of Mean F
Freedom Squares Sguare Value
59 13.0
5 1.3 0.3 1.18
54 11.7 0.2
Hosta
Deg. of Sum of Mean F
Freedom Squares Sguare Value
59 37.0
5 8.7 1.7 34
54 28.3 0.5
Lupine
Deg. of Sum of Mean F
Freedom Squares Square Value
59 61.3
5 5.1 1.0 0.9
54 56.2 1.0
Monarda
Deg. of Sum of Mean F
Freedom Squgres Sguare Value
59 57.9
5 20.3 4.1 5.8
54 37.6 0.7

Prob. LSD.05

0.015 1.7

Prob. LSD.05

0.015 1.6

Prob. LSD.05

0.999

Prob. LSD.05

0.075

Prob. LSD.05
0.999

Prob. LSD.05

0.030 0.3

94

 

Table 1.11. Overall mean 4 week regrowth ratingsy,
percentage survival and error mean square for species

of bare-root herbaceous perennials used in Experiments
1 and 2.

 

Average Overall
Regrowth Percent

 

 

Species: Rating Survival
Experiment 1
Aquilegia 4.5 94.2
Artemisia 4.7 96.5
Asclepias 3.3 76.7
Coreopsis 2.9 57.3
Dicentra 4.8 96.1
Geum 2.0 34.9
Lavandula 2.0 45.0
Phlox sub. 4.0 88.3

 

Experiment 2

Achillea 2.9 67.1
Artemisia 3.9 87.9
Phlox pan. 4.3 94.2
Salvia 2.4 64.2

 

y: Regrowth grades: 5 - 100% of regrowth potential:

4- 75%; 3 - 50%; 2 25%; and 1 - No observable
growth.

 

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HIGRN STATE UNIV.

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