A STUDY OF THE
EFFECTS OF HARDENING BF
CHRYSANTHEMUM PLANTS

THESIS FOB, THE DEGREE U? M‘ S.

George W’. Woodbury
1931

 

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A Study of the Effects of Hardening
Of Chrysanthemum.Plants

Thesis

Presented to the Faculty of
Michigan State College of Agriculture
And Applied Science As Partial
Fulfillment of the Requirements
For the Degree
of
Easter of Science

by
w. I d
George a '123_pury

1931

(:2 ,0 Wy/é/~/73/

1.

INTRODUCTION

Since the end of the 19th century the Chrysanthemum
has been improved, grown extensively, exhibited and ad-
mired until today it stands among the foremost cut flowers
raised by florists as well as amateurs. Its wide range
of color, form, size and shape, together with the com-
parative ease of culture have placed it toward the top
of the list of herbaceous ornamentals. It responds
readily to prOpagation by cuttings, and offers many
interesting variations when propagated by seed.

Under ordinary greenhouse conditions chrysanthemums
are propagated by cuttings. Such cuttings are taken from
the old plants, beginning, in some instances, as early
as December and continuing through Kay. Unless one is
growing plants for exhibition or specimens, March or
April is suitably early for taking cuttings. When so
handled, and after rooting in from three to four weeks
time, they may be immediately potted and will be ready
to bench as good sized plants during the early part of
June or later. Cuttings which are taken during the
latter part of April or early May are usually the last
ones to be benched. Plenty of first quality Chrysanthemums
are grown from plants benched in late June, and with the

smaller sorts -- pompoms, anemones, and singles, suitable

2.

flowers are produced from plants benched in July.

However, it is the general opinion of most florists

that, whatever the benching time may be, the plants

should be in first class condition when benched; not
necessarily large plants, but good healthy plants which
have been kept growing and which show no signs of having I
been checked in any way.

The months of April, May and early June are the
busiest in the year for the florists. The greenhouses
are filled to capacity. Bedding plants, snap-dragons
and other annuals grown by the average flarist must be
disposed of or put in the field before chrysanthemums'
may be benched. As a consequence, it frequently happens
that the young chrysanthemum stock is neglected. Plants
in small pots soon grow too large for the pots and dry
out rapidly, unless given very careful attention. Cut-
tings taken late are sometimes not potted, being allowed
to remain in the sand long after they become rooted.
Room will not always permit putting the plants in pots
large enough for proper growth, even if the time were
available. Plants so handled will soon become hard.
Lower leaves fall off in extreme cases and the stem
has an appearance of woodiness. Concensus of opinion
among men of the trade holds that such hardening, caused
by one factor or another, is never completely overcome
by the plants during the growing season, and that the

subseqnent crop is affected.

3.

The purposes of this investigation were :

(1) to determine to what degree the plants are
affected by hardening, and (2) to devise some treat-
ment by which the effects (if any) of such hardening
can be reduced to a minimum.

It should be borne in mind that ehrysanthemums,
unlike the cabbage, tomato and other vegetable plants,
are not purposely hardened, inasmuch as there is no
reason for doing so in view of the almost ideal con-
ditions under which they are transplanted. Hardening
in chrysanthemums exists as a result of improper
cultural conditions and is purely unintentional
on the part of the grower. However, when the plants
once become hard, efforts are usually made to overcome

effects of this condition as soon as possible.

REVIEW OF LITERATURE

Regardless of the fact that the ehrysanthemum.
has been in cultivation for some time,very few accurate
studies have been made on ultimate results of hardening.
Wiggin (ll) conducted a series of experiments on the
culture of greenhouse chrysanthemums and Laurie (5) has
obtained some interesting facts in regard to fertilizers best
suited to them. However, neither of these men, except
in a passing way, mentions effects of hardening processes
on final results.

A survey of some of the gardening periodicals,

in which chrysanthemnm growing is mentioned more as a

garden art than as a commercial undertaking, leads
one to believe that there is a distinct prejudice
against allowing plants to become checked at any
time during the growing season. Two anonymous (1)
(2) articles read in part as follows: "The shifting
of plants in the earlier part of summer should be
well attended to. If this is neglected, no good
after management will save them from losing their
leaves and looking badly in autumn and winter"; and
"---place them in small pots, keeping them at a
temperature of not less than 50° Fahrenheit. Shift
as needed." One can find a considerable number of
similar articles, all of which enunciatc the same
principle; namely, that the plants should not be
allowed to become checked at any period during their
growth. Except in the general manner quoted above,
no one states explicitly the degree or exact nature
of damage resulting from.such a check. It seems I
evident that no one has determined quantitatively
the ultimate effects of such a treatment.

Studies on the hardening process -- its cause
and effects -- have been made with the cabbage,
tomato and various other vegetable plants. Important
among these are the works of Rosa (9) (10) and Harvey
(4). Lott (7) in working with brambles made chemical
studies to determine composition in relation to

hardiness. Maximov (8) has made an extensive study

5.

of the internal factors which bring about both frost
and drought resistance in plants. He makes note of
the fact that cacti and certain other xerophytic
plants are able to withstand extreme conditions of
drought, but are easily injured by low temperatures.

The above citations include work somewhat
different from that explained in this paper. The
chief aim.of these workers was to determine the
changes of conditions induced by the hardening
processes, and also the relation of such changed
conditions t. hardiness of plants - either to
withstand low temperatures, water loss by trans-
piration, or desiccation by drying winds.

Crist (3) working with indoor tomatoes,
studied the ultimate effects of hardening processes
as regards earlincss of crop and quantity of marketable
fruits. He concluded that "When tomato plants were
hardened and then forced in the greenhouse their early
yield of marketable fruits was greatly diminished and
their total yield not materially increased.” 'He
states further that "The application of nutrient salts
to the hardened plants prior to setting them.in beds
and forcing them did not relieve the check suffered
in the hardening process."

6.

MATERIALS AND METHODS

The plants used in this experiment were good
quality rooted cuttings, all of which were taken from
Woodburyis greenhouse at St. Johns, Michigan, with the
exception of the Nellie T. Ross which were supplied
by Elmer D. Smith of Adrian, Michigan. Except in a
few cases indicated in a letter paragraph, the plants
were approximately the same age. meat of the cuttings
were taken during the early part of April.

Previous to the hardening process, a larger
number of plants in each variety were chosen than was
needed in the actual experiment so that a choice could
be made to secure uniformity of plants and degree of
hardening. Ninety-six of each variety were used,
and from 110 to 125 plants were potted when the work
was started.

0n may 5, 63 plants of Pink Chieftain were potted
in 8% inch pots and an equal number in 3 inch pets. The
letter plants were shifted from.the smaller pets to the
3's, and the former were allowed to remain in the 2% inch
pets for further hardening treatment. Plants of this
particular variety had been started during February
and consequently were somewhat larger than those which
had been started in April. Also on may 5, an equal
number of variety Gladys Pearson were potted in 2}
,pots, one half in a soil of four—fifths compost and
one-fifth peat; the other half in clean, dry sand.

7.

The latter were to be hardened at a later date.

The remaining four varieties -- Dr. Enguehard, Eager,
Nellie T. Ross and Major Bonnaffon - were potted up
in four-fifths compost and one-fifth past in a; inch
pots. Half of each variety were taken later to be

hardened.
THE HARDENING PROCESS

Inasmuch as the main object of this experiment
was to overcome, if possible, the effects of harden-
ing caused by neglect, it was thought better not to
subject the plants to conditions which would bring,
about the maximum.hardened condition. With this in
mind the following hardening was done.

On May 30, one half of the plants of each
variety were placed aside to be hardened. It will be
remembered that the hardening process had really
begun on varieties Pink Chieftain and Gladys Pearson,
the former by allowing them.to_become root bound in
the smaller pots and the latter by potting them in
the infertile sand.

The hardening process consisted only of with-
holding water from the plants. It so happened that
considerable cloudy weather prevailed during this
time with the result that the plants did not suffer
so much as they would have otherwise. For the most
,part, however, the treated plants were kept continually
dry, with only an infrequent light sprinkling with a rose

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Dr. Enguehard

Plants at Benching Time.

Unhardened plants on Left; Hardened
plants on Right.

1.2.

sprayer. Meanwhile, the remaining (unhardened) plants
were kept at as near optimum.moisture conditions as was
possible by frequent waterings and syringings.

The accompanying photographs show the comparative
size and condition of the plants at the time of benching.
In all cases there was a marked.difference in the growth
of the plants. From.the standpoint of the problem.it
should be borne in mind that this check in the plant
growth is of greater importance than the difference in
size.

All of the plants used in the experiment were
benched June 24, as is shown in Fig. 1. It will be seen
that the hardened and unhardensd plants were checked
against each other in cash plot, and that each plot
could be checked against any or all of the remaining
plots. This made possible a large number of comparisons.

Inasmuch as the houses in which the plants were
grown run north and south, it was not thought important
to change the location of the varieties from one plot
to another or from one bench to another. For the sake
of convenience and to avoid confusion in later
determinations, each variety maintained its same position
with respect to the bench throughout the entire three
benches and twelve plots.

Three benches were used, each 22 feet long and

4} feet wide. One such bench accommodated four plots,

13.

each with 48 plants, 8 of each of the six varieties
running lengthwise of the plot. Two pine boards one
inch apart separated one plot from another. A glance
at the accompanying diagram affords a definite idea of
how the plots were arranged. Each plot represents an
area of 24.75 square feet.

311 standard varieties of chrysanthemums were
used. These represent a period of bloom.of about a
month, the latest one, Nellie T. Ross, a rather late
mid-season bloomer maturing about November 31 and the
earliest, Pink Chieftain, maturing its first blooms on
October 23. It will be noted that neither the early
nor late extreme of the season was represented. The
varieties at hand, however, show enough difference
in time of blooming to be representative. Pompous,
anemones and singles were not included in this experi~
ment and owing to the difference in growth of various
sorts, experimental data at hand might not be representa-
tive of all sorts as a whole. However, these varieties
are all good commercial sorts that are regularly in-
cluded in varietal lists by florists who raise chrysanthe-
mums for profit.

Twelve different treatments given on the twelve
respective plots were as follows:

1. One pound 2-isea commercial fertilizer in-
corporated in the soil at benching tune, followed by'a

one inch German peat mulch one week later.

14

,8. One pound bone meal worked into the compost
at benching time, with a one inch manure mulch applied
one week after benching.

3. One pound 2-16-3 commercial fertilizer mixed
into compost at benching time. In this plot the hard .
plants were notched with a sharp knife at a point above
the hardest portion of the plant.

4. One pound of *Vigoro" was incorporated into
the compost at benching time.

5. One pound 2-16-2 commercial fertilizer was
mixed-with the compost at benching time.

6. One half pound of ammonium sulphate was worked
into the compost at benching time, followed on July 17
by two ounces of ammonium sulphate in solution and applied
at the time of watering.

7. This plot contained half German imported pest
and half soil by volume, mixed together. The hard
plants in this plot were set deep so that the hardest
portion was below the surface.

8. Half pest and half soil were mixed together
in this plot.

9. No treatment was given except that the hardened
plants were injured as in plot three.

10. No soil treatment was used, but the hardened
plants were set deep as in plot seven.

ll. All plants in this plot were pinched back two
or three nodes one week following benching.

15.

12. No treatment was given either soil or plants
in this plot.

The compost used in the beaches was taken from
the compost pile at the greenhouse, and was made up of
stable manure and sod, and was of a loamy nature. It
should not be understood that the above treatments re-
present ordinary commercial methods of soil treatment
for chrysanthemums. In years past, and also at the
present time, mulching with manure has been a common
practice among many growers of ohrysanthemums. Such
mulching, however, is rarely done until after the bud
is taken and is often substituted for or supplemented
by regular feedings with manure water until color shows
in the buds. Manure mulch used in plot 2 would not
serveto "feed" the plot, but more as merely a mulch
that supplied some additional plant food. Edmonds and
Laurie (5) from rather extensive experiments with
chrysanthemums report that a peat mulch promotes a
marked increase in growth over those plants where no
application is made. They go further to state that
past supplies desired acidity suitable for chrysanthe-
mnms. They also state that super-phosphate applied at
benching time is very useful in starting growth and
inducing earliness. Bone meal was found by them.to be

of little value for such a short season crop.

16.

The mechanical treatments resorted to in this
experiment were with the idea in mind to dispose, as
far as is possible, of the hard wood. It was thought
that roots might develop on the stems at the point of
inJurY. If this occurred, resulting growth would be
unhardened. Where no injuring was done, the idea was
to dispose of the hardened tissue by submerging it.

Practically the same thing is true in the case
of the pinched plants, except that the new "breaks" re-
sulting from.the pinching process would be unhardened,
the resulting difference, if any, would be in the time
required for such "breaks" to appear and develop.

The check plot (no. 12) represents treatment usually
given to plants at benching time. In commercial work,
however, feeding would follow'after the bud had been
isken. In none of the twelve plots was feeding done. It
seems probable that larger blooms of perhaps better quality
might have resulted if feeding had been done, but there is
no reason to believe that comparative results would have
been altered by such treatment.

A study of the pH values was made in each plot.
Results are shown in table 1. In the peat plots the pH
is somewhat lower. In these two plots the early growth
seemed more succulent and a lighter green in color. Wiggin

(11) reported 6.5 as the pH at which chrysanthemums do

17.

best. Wildcn‘ reports a somewhat lower pH of 5.6

as being best suited.

Table l.- Showing pH of soil in each plot. Determinations
were made several weeks after the plants had become
established.

Plot No. pH
1 7.2
2 7.8
s 7.5
4 7.5
s 7.4.
e 7.6
7 6.8
s 6.8
9 7.3

10 7.4.
ll 7.3
is 7.s

I'Unpublished data obtained from.eXperiments at Rhode
Island State Agricultural College.

18

EXPERIMENTAL RESULTS

Data were obtained on rate of growth, quality
of bloom, date of maturity and final height of hardened
plants as compared with the unhardened plants. Quality
of bloom depends on size, color, substance, form, keeping
quality, foliage and length of stem. Of these, size of
bloom.and length of stem are most conveniently measured.
Color, form, keeping quality and substance were observed

and suitable notes made.
EFFECT OF HARDENING UPON LENGTH OF STEM

Table 2 shows the average length of stems of all
hardened and unhardened plants in each plot, irrespective
of variety, at the beginning of the experiment. Similar
averages are shown for the same plants at its end. In
general the figures are representative of those for any
one of the six varieties used.

It will be seen from these data and the accompany-
ing photographs that the unhardened plants had a distinct
advantage in height over the hardened plants. It was
important in this experiment to note the rate and total
increase in growth, as well as weekly increment, to de-
termine whether or not the hardened plants overcame this
check in growth, and if so, at what time during their

season of growth. If, on certain plots, the difference

19

between.the hardened and unhardened plants soon becomes
less, then that particular treatment obviously was bene-
ficial, as compared with any plot where this difference
persisted throughout the experiment. The figures in
Table-8 show that in only one case, plot 5, did the
average of the hardened plants come up to or exceed the
average for the soft plants. In the variety Gladys
Pearson the hardened plants had caught up with the

soft plants on August 82, and growth proceeded at about
the same rate from then on. In Chieftain, where there
was mmre difference to start with, the hardened plants
were practicallyequal to the soft plants at the end of
the season. major Bonnaffon plants were on a parity by
September 8. Dr. Enguehard, where difference was slight
at the beginning of the experiment, showed the hard plants
catching up early -- about the end of July. In Nellie
T; Ross and Charles Roger, growth in the hard and soft
plants was at about the same rate pretty much throughout

the entire season.

20.

Table 2.- Showing Average Height of Hardened and Unhardened
Plants on each plot at benching time and at
maturity. At the right is shown average size
of bloom of these plants.

 

 

 

Ave.Height Ave.Ht. at end 'Ave. diam.
at beginning; of experiment of bloom.
Unhardened Hardened 'Unhardened Eard- Unhard- Hard-
inches inches ened. ened ened
ZPlot No. inches inches inches
1 8.67 5.04 47.8 45.9 5.22 5.07
2 7.56 4.78 44.88 42.00 4.81 4.61
3 7.71 3.50 42.00 41.23 5.01 4.63
4 9.07 4.58 44.00 41.50 3.28 5.10
5 8.20 5.60 40.79 41.37 4.89 4.75
6 9.06 . 5.22 43.25 40.33 5.19 4.85
7 8.96 4.21 44.52 42.79 4.80 4.88
8 9.38 5.41 45.62 42.17 4.97 4.83
9 8.86 4.69 47.37 41.16 5.19 4.88
10 7.86 7.59 41.37 39.54 4.97 4.82
11 6.31 4.32 37.41 34.00 4.94 5.15
12 9.21 6.95 42.50 39.17 5.06 4.95

21.

As previously stated, no other plot showed
average height of the hardened plants exceeding that
of the unhardened plants in the course of the growing
season. In a few instances, i.e., with certain varieties
in certain plots this took place, but not consistently
enough to change the order for the plot.

Growth, percentage of growth, and weekly increments
were plotted for each variety so as to show the averages
for all the individuals of both hardened and unhardened
plants in each plot. The resulting curves show graphically
what happened to all lots during the experimental period.
The curves are consistent. Percentage of growth was
calculated by dividing the weekly increment, averaged
from the four unhardened and four hardened plants of
each variety in each plot, by the previous weekly
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other words, as the plants became more nearly equal in
height, rate of growth was more uniform. Weekly increment
varied with the greenhouse conditions prevailing throughout
the week, with little difference being apparent between

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51

The important feature brought out by the
figures is that, though in general the hardened plants
did not catch up with the soft plants in height,
there was none of them without stem of sufficient
(and in many cases more than sufficient) length
for first class marketable‘filooms. Furthermore,
though no exact correlation coefficients between
length of stem.and size of bloom were calculated,
there would be little reason for assuming that such
a correlation existed. Wiggin (12) in experimenting
with cultural methods for chrysanthemums on varieties
William Turner and Yellow Turner, found that no corrdb
ation existed between length of stem and size of bloom.
”In only 3 out of 30 plots was the coefficient of
correlation equal to four times the probable error."
He states further that any stem beyond what is good

commercial length has no advantage.
EFFECTS OF HARDENING UPON SIZE OF BLDOMS.

Terminal buds were taken on all of the plants
in all plots. With all other things being equal, this
should bring about a uniformity of bloom as regards
date of maturity, size, color and quality.

The only measurement made of the blooms was the

diameter. A square piece of card board, graduated with

32.

different sized concentric circles, with a slit on

one side for the insertion of the stem, provided the
most convenient method for making these measurements.
Diameter alone should not be used as a criterion for
determining size, as depth and fullness are also
important factors. However, in making measurements,
where extreme cases were in evidence, some consideration
was accorded these other factors, and the figures as

recorded were comparable.

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54

Table 2 shows average size of bloom.from
unhardened and hardened plants in each plot, regard-
less of variety.' Table 3 shows size prevailing in
varieties regardless of plot, and table 4 gives
average size of bloom from hardened and unhardened
plants irrespective of plots. Where buds had been
injured by one agency or another, necessitating the
taking of a lateral bud, the blooms from such buds
were discarded and not used in computation of results.
Consequently, in almost every-instance, the number of
unhardened plants producing blooms was not the same as
the number of hardened plants producing blooms. Total
number of blooms used is recorded in each instance.
From these data a slight tendency toward larger blooms
among the soft plants is apparent. As is natural,
size varied to a considerable degree from one variety
to another. In all instances, however, these differences,
apparently brought about by treatment, are too slight to

be significant to the commercial producers.

 

I - ‘I .W' -.—..— w—w r
=——— .__ _

 

35

Table 4.» Showing average size of blooms from
Unhardened and Hardened plants in each
_fivariety covering all twelvegplots.

Average size of Bloom

 

 

Inches

Unhardened Hardened
Variety gplants ,plants
Major Bonnaffon 5.03 4.80
Dr. Enguehard 4.29 4.08
Charles Rager 4.82 4.63
Chieftain 4.96 4.67
Nellie T. Ross 5.68 5.71
Gladys Pearson 5.36 5.38

 

f

56.

EFFECT OF HARDENING UPON TIME OF
MATURITY OF BLOOM

From a study of Table 3 it will be seen that the
earliest variety, Pink Chieftain, showed a wider variation
between the two treatments than did any of the others.
Nellie T. Rose and Gladys Pearson, among the last varieties
to bloom, showed the least difference in size of bloom
from one treatment to another. It would seem.natural
to expect this to be the case. The earlier plants had
reached a greater degree of maturity at time of harden-
ing than had the late plants, hence the check would be
more lasting in effect. Loomis (6) found that injury
from transplanting increased with maturity; If one
considers transplanting itself as a hardening process
to some extent, the above results would seem.in order.

All blooms were measured at a time when they were
apparently at their maximum as regards size, and at the
time they would have been out for commercial use as
first class flowers. With such a standard as a basis,
all blooms were measured at a time when they had
attained the same degree of maturity. Table 5 shows
number of blooms of both hardened and unhardened plants
cut on the dates given. Here, as with size of bloom,
the greatest differences are noted in the Pink Chieftain,
which covered a blooming period_of about twenty days,
as against Nellie T. Ross, all blooms of which had

reached the same degree of maturity on a single day.

 

 

 

Table 5.- Time of maturity of blooms in each variety from Unhardened and Hardened plan.

 

lO - 30

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Date 10 — 23 lO - 24 10 - 27 10 - 28 ll - 3 ll - 5 11 - 11
Unhard- Hard- Unhard- Hard- Unhard- Hard- Unhard- Ward— Unhard- Hard- Unhard- Hard- Unhard- Hard— Unhard- Hard-
Treatment ened ened ened ened ened ened ened ened. ened ened ened ened ened ened ened
Gladys Pearson
Dr. Enguehard “
True fta in 2 0 -..._. 3 ”-2 9 9 e 6 n4 9_ 4 5 3 5 a
Bonnaffon z__ 1 5 3 3 15
Nellie T. Ross .4
Charles Rager 3 1, 32:. 30
Date 11 - 15 ll - 16 ll - 17 ll - 18 11 - 21
Unhard- Hard? Unhard- Hard- Unhard- Hard- Unhard- Hard- Unhard- Hard-
Treatment ened ened ened ened ened ened ened ened. ened ened
Gladys Pearson 3 31 26 _, 8 14
Dr. Engue‘hard F2. - 40 159 2 :3
Chieftain l 3
Bonnaffon 15 15 2 5 l 5 PP
Nellie T. Ross 43* _§$
Charles Rager 6 ll

 

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38.

In Gladys Pearson, unhardened plants came into bloom
earlier, but several plants of this variety were lost

and the results, therefore, are not so reliable.
EFFECT OF HARDENING 0N QUALITY’OF BLOOMS.

The commercial grower desires flowers of fairly
good size, uniform throughout, with a strong stem, good
substance and color of both foliage and flower. Conditions
A which favor production of such chrysanthemums are the con-
ditions the florist seeks to establish.

Fig. 5 shows eight blooms of Nellie T. Ross from
plot 8. Stem lengths and size of.blooms are given. To
facilitate photographing, a portion of the stems was re-
moved previous to taking the picture. Certainly, if
these four blooms from hardened plants were mixed with
the accompanying four blooms from.soft plants, no expert
on chrysanthemums would be able to distinguish one from
the other. In quality of foliage, flower and stem there
is no discernible difference. Fig. 6 shows blooms of
Gladys Pearson from Plot 7, but their identity had been
lost before photographing. Stems were cut off here as is
explained above. These varieties were chosen for photo-
graphing only because the flowers mstured at the same time.
In view of the figures at hand, and in light of observations
made, it is safe to say that the same results would have

been obtained from any other variety in any other plot,

except for the irregularity inreaching maturity.

39.

 

 

 

 

 

Variety Nellie T. Ross Plot 8
Left: Blooms from Hardened Plants.
Right: Blooms from Unhardened Plants.

 

 

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. '1‘“ t "‘ "I

 

 

 

Variety Gladys Pearson Plot 7
Identity of Blooms‘Unknown.

40.

EXTREME HABDENING.

Shortly after September 15, a few plants of
varieties Gladys Pearson and Major Bonnaffon were taken
from the propagating bench in the greenhouse. These
were surplus stock which had not been used, and there
being no use for the propagating bench during the summer,
the cuttings were allowed to remain in the sand after
they had rooted. The only water that they had received
was that which had splashed on them.when nearby plants
had been watered. As a result, these plants had reached
an extreme state as regards hardness. To supplement the
data being obtained by experimental treatments, 50 or 75
of these plants were potted in 3 inch pots in fertile
compost with some sodium nitrate added. No data were
taken, but the plants showed but few signs of recovery,
sent out a terminal bud, and bloomed when about one foot
high. The blooms were small and inferior. This shows
that when hardening has reached an advanced stage, re-

covery cannot be expected.

DISCUSSION OF RESULTS.

From data obtained in this work and from a care-
ful study of the various features involred, it can be
said that chrysanthemum plants whch were hardened by
one process or another produce marketable blooms of as

good quality as do plants which have been given the best

of treatment. The differences between them are too small

41.

to be significant. At least this holds true for such
degrees of hardening as were obtained in this experi-
ment. There are, however, a few reservations which
should be made. In growing chrysanthemums, there are
several important features which are very likely to
have a bearing upon the crop. Important among these
is the time of benching. This usually has a direct
bearing upon the conditions of the plants when benched
as regards maturity, hardening, and size. It seems
reasonable to believe that, as time goes on, plants
left in pots will become harder than if placed in the
bench at the preper time. June 24, the date on which
the plants of this eXperiment were benched is not late
----neither is it very early. It represents a time at
which many florists are starting to bench, some of the most pro-
gressive, perhaps, have benching almost completed, and
a lagging few have not yet started preparations.

The writer has had opportunity to observe, on
several occasions plants benched late that had become
very much hardened by remaining too long in the small
pets. Such plants lose most of their lower leaves,
have every appearance of being checked in growth, and
finally produce small blooms and poor quality stems
and foliage. This took place where no treatment was
given to invigorate the hard plants and benching was

done from two to four weeks after June 24.

42

SUFUDIARY

1. This experiment was carried out to observe
effects of hardening on chrysanthemums. Various treat-
ments were used to reduce other differences to a minimum.

2. Six mid-season varieties were used which
blossomed over a period of about a month. Twelve
different treatments were given; in each plot half of
the plants had been hardened and half well grown.

3. The hardening process, which consisted
primarily of withholding water, brought about a distinct
check in growth, as indicated by comparative size of
hard and soft plants.

4. Only one plot, No. 5, where 2-16-2 commercial
fertilizer was applied at benching time, showed an
average height of the hardened plants greater than the
average of the soft plants. The difference was not
great enough to be considered significant.

5. Hardening of plants had no significant effect
upon time of flowering, size, nor quality of bloom.

All stems were of more than sufficient length for
marketable blooms.

6. It is possible that a longer period of harden-
ing, followed by later benching, would have produced
different results, although no data are available to

substantiate such a statement.

43.

Acknowledgments.

The writer wishes to express appreciation
for assistance given him in the pursuance of this
problem. Especially is he indebted to Professors
V. R. Gardner and C. E. Wildon for help in organiz-
ing and planning the work and assembling and criticiz-
ing the manuscript; and to Dr. J. W. Crist for his
suggestions in interpreting and presenting the

data.

1.
2.

5.

4.

5.

6.

7.

8.

9.
10.
ll.

12.

44.

LITERATURE CITED.

Anonymous. Chrysanthemum Culture. Gardeners'
Chronicle. 2: 5277. 1842.

Anonymous. Chrysanthemum Forcing. Gardener's
Chronicle. 3: 229. 1843.

Crist, J. W. The ultimate effect of hardening
tomato plants. Mich. Agr. Exp. Sta. Tech. Bull.
89. 1928.

IHervey, R. B. Hardening processes in plants and
deveIOpments from frost injury. Jour. Agr. Res.
15’ NO. 20 19180

Laurie, Alex and J. B. Edmond. Fertilizers For
Greenhouse and Garden Crops. A. T. De La Mare 00.,
Inc., New York. 1929.

Loomis, W. E. Studies in the transplanting of
vegetable plants. Cornell‘Univ. Exp. Sta. Mem.
8?. 19250 ‘

Lott, R. V. Correlation of Chemical Composition
with Hardiness in Brambles. Mo. Agr. Exp. Sta.
Res. Bull. 95. 1926.

Maximov, N. A. Internal Factors of Frost and
Drought Resistance in Plants. Protoplasma.
VII: No. 2. 1929.

Ross, J. T. Pentosan Content in Relation to Hardiness
of Vegetable Plants. Amer. Soc. Hort. Sci. Proc. 1920.

Rosa, J. T. Investigations on the hardening process
in vegetable plants. Mo. Agr. Exp. Sta. Bull. 48. 1921

Wiggin, W. W. Studies on the reaction of greenhouse
soils. Amer. Soc. Hort. Sci. Proc. 1928.

The Culture of Greenhouse Chrysanthemums.

 

Ohio Agr. Exp. Sta. Bull. 439. 1929.

 

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