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DEVELOPMENT OF THE FRUIT BUDS '

OF THE PEACH IN RELATION TO
WINTER INJURY

THESIS FOR THE DEGREE OF M S
L. R. Stanley
. 1931

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DeveloPment of the Fruit Buds of the
Peach in Relation to Winter
Injury.

Thesis

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

by

L. R. Stanley

m

1931

W M 470/

/% 6M [4.

l.

EVELOPMENT OF THE FRUIT BUDS OF THE PEACH
IN RELATION TO WINTER INJURY.

L. R. Stanley.

The tenderness of the blossom buds has rather
constantly and effectively limited the areas in which
commercial peach production is attempted and has thus
made peach growing more profitable in the favored
regions than it would have been otherwise. Within the
favored areas, however, bud tenderness becomes a costly
factor all too frequently. In so far as Michigan
orchards are concerned, bud killing in winter is far
more important than it is during the spring. The say-
ing rather common among peach growers "if the buds
reach March 15th, undamaged, a crop is assured," is
not far from the truth. Consequently, any study directed
toward diminution of bud killing in this state should
consider principally winter conditions.

There has been a rather general opinion, based
on analogy and observation, that the stage of develop-
ment attained by peach buds is a factor in winter hardi-
ness; specifically, that the more advanced a bud is,
the more tender it is. In the sour cherry, for example,
under Wisconsin conditions (26) the buds which are
differentiated first and are more advanced in develop-
ment at the beginning of winter are more tender. Under
Missouri conditions (7), advancement of buds during mild
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2.

weather in the winter makes them more tender to rather
ordinary winter weather.

In Michigan there have beenfrequent observations
to the effect that unusually warm weather in October
and November develops peach buds to a point which makes
them unusually tender during the ensuing winter (5).

In Kassachusetts (2) abundant sunshine, rather than
high temperatures during this period, seems to cause
tenderness to winter freezing.

These various reports might be interpreted,
though not necessarily, as indicating that the stage
of development is the decisive factor in determining
hardiness of buds. If these reports are true, then
it is a matter of considerable practical importance,
because evidence secured in Iowa (21) in connection
with apples, and in Fisconsin (25) with sour cherries,
indicates that the time of bud differentiation and the
development attained before cold weather sets in may
be influenced to some degree by cultural practices.

The study reported in this paper was aimed to
determine:(1)whether recognized varietal differences in
bud hardiness of the peach are related to differences
in the stage of development at a given time, and
(2) whether shoots of different types of vigor show
differences in the stage of deveIOpment of the blossom
'buds. To establish these points it was necessary first

to determine what might be termed normal progress in

5.

bud development.

REVIEW OF LITERATURE.

Duhamel du Monceau (15) in 1758, reported that
flowers with calyx, petals, stamens and pistil can be
distinguished in the peach bud in February. In break-
ing the tips of the anthers in February he observed
that Juice and grains of dust issued from the interior
of the anther. The seed could not be seen.

Geleznoff (15) working at Mescow during the
winter of 1847-1848, made some very careful observations
on the winter rest period of blossom buds of the elm
and other hardy perennials. As reported by Askenaay,
he supposes from the results of his experiments, that
the standstill in the development of buds during the
winter is only apparent. All buds which he studied
made progress during January, February and March.

The cold decreased very rapidly towards spring and
thawing weather occurred frequently; yet Geleznoff

did not believe that progress occurs only during the
latter period, since he observed a progress in the
formation of the buds in the 67 days from December 23
to February 8. During this period the temperature
never rose above freezing. He observed new formations,
as of pollen in the larch and integument in the elm,
during the uninterrupted freezing period.

Askenasy (1) working in the western part of

 

4..

Germany, reported in 1877 that the development of the
blossom buds of the sweet cherry divides itself into
two periods separated by a period of rest or very slight
growth. The two periods fall in different years; the
rest period extends from the end of October to the
beginning of February; or approximately three and a
half months. From his results, he concluded that it
was clear that the blossom buds of the cherry undergo,
between the end of October and the end of January, a
change in their nature which is to be recognized, not
in an increase in weight or size of the parts, but only
in changed reactions to higher temperatures. It is
easy to suppose that this change is of a chemical
nature. One can, for example, suppose that during

this time in the growth-capable parts of the bud, a
material similar to diastase is formed, which spreads
out into the other tissues of the stem and there brings
into solution the starches and other reserve materials
which are stored in certain cell complexes, especially
in the pith rays of the wood. It may be possible that
in these cells themselves, without influence on the part
of the buds, a chemical change takes place.

Goff (16) apparently conducted the earliest in-
vestigations in the United States on fruit bud development
and some phases of the problem of winter killing of fruit
buds and the factors which influence hardiness. Samples

of buds were taken weekly from a Bokara peach tree that

5.

had been planted in the spring of 1898. After passing
through the severe winter of 1898-1899 with little
injury, the tree made very thrifty growth, and the bud
samples were taken, beginning on July 5, 1899. The
side buds, each destined to become a flower had it been
permitted to remain on the tree, showed at this time no
evidence of the forthcoming flower. In samples taken
on September 14 the crown showed a decided thickening
as compared with side buds of the previous samples.
This was, undoubtedly, an indication that the flower
was soon to appear. Other samples taken a week later
showed unquestionable indications of flowers. Three
weeks later, on October 4, the flowers appeared much
more advanced; the calyx, petals, stamens and pistil
were clearly discernible. It appears therefore, that
in this variety of peach, the flowers began to form about
the middle of September.

Tufts and Morrow (26) have summarized the in-
formation obtained from different parts of the country

on the time of initial differentiation of peach fruit buds:

Georgia June 14
California June 30
Virginia July 7
Wisconsin Sept.21

Tester (27) found in Nebraska that by September
14 two whorls of stamens had been formed in the fruit
buds of the peach.

Wiggans (28) during the progress of his work in

California, reported differentiation occurring at

approximately the same time in all sections of the state
in which his studies were conducted. He found environ-
mental conditions during winter producing no checking in-
fluence on fruit bud development of the pear or apricot
under California conditions.

Bradford (3) studying fruit bud differentiation
of the apple under conditions obtained in Oregon, found
that there was a rather uniform stage for all varieties
studied as they went into winter condition. There was
considerable range in the time of differentiation of buds
in different positions on the tree, but all apple
blossom buds go into winter in practically the same
stage of development.

Bradford (4) later found in Missouri that there
was considerable difference in the stage of development
of apple buds going into winter, and that there was
marked difference in the way these buds developed during
the winter. On the basis of his analysis of the Mikesell
records from Wauseon, Ohio, he concluded that accumulations
of heat in November and December have some influence in
the forwarding<t Late Crawford peach blossoms toward
opening. There is a tendency, though not very strong,
towards an association between lower temperatures in
October and low summation between November 1 and blossom-
ing in the peach. This may be associated with some effect
of the high October temperatures in prolonging, or of the

low temperatures in breaking, the rest period in the peach.

7.

Morgan (23) found in New York that the blossom
buds of the apple started to develop earlier in the
spring than those of the peach, but that the peach rapidly
overtook it.

Drinkard (11) reported from Virginia that the
peach is more responsive than the apple to higher
temperatures during the winter.

Chandler (7) in Kissouri found hardiness of peach
buds, when in a fully dormant condition, to be greatly
increased by continuous low temperature preceding the
date at which the temperature goes low enough to kill.
Some varieties of peaches have a longer rest period than
others and are, therefore, started into growth more
slowly by warm periods in winter. Trees making a late
vigorous growth (as cut back trees do) are later in
finishing their resting period and are therefore in less
danger from injury by cold following warm periods in
December and January. The hardiest buds are those at
the base of fairly strong whips.

Lazenby (22) reported, in Ohio, "the most vigorous
peach buds are not at the end of the shoot, but on the
part first formed or lower half."

In regard to the winterrest period of buds,
Howard (19) found all forms of rest to be caused by un-
favorable external conditions, and these conditions
determine both the time of occurrence and the degree

of intensity of the period of rest.

8.

He found the peach to have a resting period of about
six weeks (in Missouri), and that when peach buds are
killed it is because of their habit of premature growth
during warm days in late winter. Every fruit grower
knows that there is no danger of growth taking place in
early winter because trees are then in the midst of the
rest period. Thus it seems that the rest period of the
peach is a very important factor in determining the

hardiness of the fruit.

Coville (lO), commenting on the effect of cold
in stimulating subsequent plant growth, says "the period
of chilling required for the peach is so short that, in
Georgia, unusually warm weather in December sometimes
brings the trees into bloom and the crop of fruit is
destroyed by the freezes that follow." This occurrence
of premature blooming has also been observed in Texas
by Brison (6).

Roberts (25) working with sour cherries in Wisconsin
found that the primary killing in the buds seems to be
confined to those cellsvvhich have a large central
vacuole and that the vacuolated condition of the cytoplasm
of cells in the region affected renders them more
susceptible. The appearance of a large central vacuole
is taken as evidence of the approach of maturity of the
cells. The rate of maturing would be materially affected
by the nutritional and growth conditions of the trees."

This fact gives promise of success in attempts to re-

duce the injury through cultural means.

9.

Johnson (20) secured results which suggest a
definite relationship between air temperature and the
rate of increase in the moisture content of peach fruit
buds. There can be little doubt, however, that other
conditioning influences operative before January 1
determine the manner in which these buds respond to
temperature. The rate of increase in the moisture
index after January 1 was found to vary, in five
different years, as the sum of the effective daily

mean temperatures above 43°F.

METHOD OF PROCEDURE.

For the purposes of this study, fruit buds
samples were collected in two localities, the Michigan
State College orchards at East Lansing, and The
Corporation Farm Orchards at South Haven (three miles
east of Lake Michigan).

The South Haven section is generally conceded
to be one of the best peach growing sections in the
state because of its proximity to Lake Michigan and
its numerous desirable orchard sites. East Lansing,
on the other hand, is in a general farming section
that is not favorable to fruit growing, especially
peaches. It derives less benefit from the moderating
influences of large bodies of water. The college orchard
stands on a site which gives practically no protection

from low temperatures during winter or early spring.

10.

In fact, because of low winter temperatures, good crops
of peaches have been secured in only four of the past
eight years.

Samples were taken from hearing trees in moderate
vigor, previously handled according to the usual orchard
practice in Michigan which consists of cultivation and
cover crepping.

Buds were taken from the same trees at each
collection, and as far as possible, they were taken from
the south side of the trees. Two classes or types of
buds were preserved:

(l) buds on spurs of 2 inches or less in length.

(2) buds on vigorous growth over 12 inches in length.

To secure a comprehensive picture of the cycle of
bud development, samples were taken at intervals of two
weeks from July 30 to April 15, except that monthly
collections were made during mid-winter.

This schedule was followed closely in the collection
of material at South Haven. The sampling at East Lansing
was more or less irregular, to fit unusual weather periods,
but comprehensive enough to give a fair comparison. The
buds used in this work were collected at South Haven
during 1926 and 1927, while at East Lansing the samples
represented a range of seven years from 1922 to 1928.

This gave a basis for comparing bud development during

different years when weather conditions varied.

ll.

HANDLING OF BUD SAMPLES.

After the buds were removed from the tree, the
scales were cut away on two sides of the bud to
facilitate the entrance of the killing fluid and later
to aid in subsequent infiltration. The cutting away
of the bud scales was done in the orchard and the buds
were placed immediately in Bilson's killing fluid.

The buds were infiltrated with colloidin, sectioned with
a sliding microtome to a thickness of 25-40 microns,

and stained with Delafield's Haematoxylin. This stain,
as reported by Roberts (25), does not stain dead tissue
and in buds that had beensdightly injured by low tem-
peratures it was possible to differentiaéz:fiegd afldiving
tissue. The dead cells could be distinguished by their

brown color, while the live tissue took the purple stain

of the haematoxylin.

VARIETIES OF PEACHES STUDIED.

Hill's Chili, a variety once popular because of
its winter hardiness, was selected for study as offering
rather extreme contrast with those varieties that are more
tender in bud. Elberta was selected because of its
commercial importance and the fact that under Michigan
conditions it is rather tender in bud. Other varieties
were used for comparison with the hardy Hill's Chili and

tender Elberta. The list of varieties from which bud

12.

samples were taken and their classification on the basis
of hardiness as suggested by Chandler (8), Hedrick (18),

Johnston (21) and others follows:

 

Very Hardy Hardy Tender
Hills Chili Kalamazoo Elberta
Gold Drop South Haven Late Crawford
Fitzgerald J. H. Hale

With the help of a micro-projector drawings were
made, all on the same scale so that bud advancement and
increase in size could be accurately compared. Use of a
Micro-Teaser lens“ enlarged the field sufficiently to
include groups of three collateral buds where that was
deemed necessary to the proper interpretation of the re-
sults. Microphotographs were taken of several bud
sections to show more detail than could be shown with a

micro-projector drawing.

PRESENTATION OF RESULTS.
Differentiation of Fruit Buds of the Peach.

 

Sections of prospective blossom buds of the Hill's
Chili, Elberta and South Haven varieties, from material
gathered July 50, August 15 and August 30, 1926, at East
Lansing and South Haven, showed no evidence of blossom bud
differentiation. This is illustrated by Plates 1(A,B),
Plate IV(A,B,C), Plate VII(A,B,C), Plate X(A), and Plate
XXII(A,D). Samples gathered on September 15, however,

show a relatively advanced stage of differentiation, with

13.

singular uniformity among varieties, between different
locations, and between buds taken from spurs and vigorous
wood. This early stage of differentiation is illustrated
by Plates 1 (c), IV (d), VII (d), X(B), and XXII (B,E).

Fruit Bud Advancement During the Autumn.

 

From September 15 to December 18 the buds advanced
rapidly, as shown by comparison of Plates 1 (E,F), II (A),
VII (E,F), VIII (A,B,C), X (C,D,E,F), XI (A,B), XXII (C,F).
XXIII (B,D). This development is extremely rapid during
the latter part of September and October and slower during
November and early December. There is a striking uniformity
in the rate of advancement in buds of Hill's Chili, Blberta,
South Haven and J. H. Hale, and there seems to be little,
if any, difference in the stage of develOpment attained by
fruit buds on spur and vigorous wood growth during this
period.

Under conditions prevailing in Michigan during the
fall of 1926, all fruit buds of the peach varieties studied
went into winter in practically the same stage of develop—
ment. Consequently, any varietal differences in hardiness
as shown by resistance to winter cold, could not be attri-

buted to unequal fruit bud deveIOpment previous to December 15.

E rly Winter Development and the Rest Period.

 

Between November 15, 1926, and January 1, 1927,
buds changed but little except for a slight increase in

size; this increase seems to have continued also during the

14.

latter part of December. (See Plates II (A), V (C),
VIII (C), XI (B), an XXVI (B,C,D). This point cannot
be asserted positively in the absence of exact measure-
ments on a large number of buds; nevertheless, it was
rather consistent in the material examined. he period
between mid November and the first of January is the
one of least activity in bud development during the
entire progression from differentiation to blossoming
and it would correspond closely to the rest period as
defined physiologically.

At Just what time the rest period begins and
closes, it is impossible to state, but during the years
under consideration in this study, it is probable that
the sub zero temperatures occurring during the latter
part of November and early December were instrumental
in breaking the rest period. Evidence of this was
obtained in examination of bud sections taken in January

which showed some development over those of December 18.

Late Winter and SpringDevelqpment.

 

Between January 15 and April 15, bud advancement
was naturally slow at first, becoming more rapid in late
march. This is represented by Plates II (C,D,E,F),
III (A), V (E,F), VI (A,B,C), VIII (D,E,F), IX (A.B),
XI (D,E,F), XII (A,B,C), XXII (I), XXIII (E) and XXIV (D).
During February and march there was rapid develOpment of
the pollen. In February the microspores were differentiated

from.the pollen mother cells and in March the tetrad stage

15.

was prominent.

By late March or early in April the pollen grains
were practically mature. No significant difference in
the rate of bud advancement could be detected in buds
of different varieties, or from buds taken from either
spur or vigorous wood growth. Plate XXXIV (A) shows a
longitudinal section through an anther of Elberta bud
collected on April 15. This drawing was made with a
higher magnification than that used for the other plate
drawings. In several sections from material gathered
on February 28, ovules could be clearly distinguished.
They had not appeared in material gathered before this
date. (See Plate V (F).

Comparison of the Rate of Fruit Bud DeveIOpment in Different
'Varieties of Peaches. V‘ VI

 

Plates XIII (A,B,C,D,E,F), and XIV (A,B,C,D,E,F)
present a comparative study of the rate of advancement in
spur fruit buds of the Hill's Chili and Elberta varieties.
Plates XV, XVI and XVII show a similar comparison of fruit
buds from vigorous growth of the same varieties. Study
of these plates again reveals the uniformity in develop-
ment of the fruit buds of these two varieties on the same
dates throughout the entire period of bud formation.

Plate XVIII gives a comparison of the stage of development
attained by Elberta spur buds on approximately the same
dates at both South Haven ani East Lansing. There is no \E

apparent difference in the stage of advancement on the

same dates for this variety. Plate XIX presents a

16.

comparison of Elberta spur buds on approximately the same
dates, but from samples taken in different years. There
is, apparently, a close correspondence between bud
development attained on given dates during 1923, 1926

and 1928.

It is of interest to note that microphotographs
of peach buds made by Munn (2;) in 1912 when he was
studying the relation of cover cropping to fruit bud
development show practically the same stage of advance-
ment as those for equivalent dates in the years covered
by this present study. Hunn's bud samples were taken
from the Barden Orchard near South Haven.

Plate XX (A,B) indicates that Gold DrOp fruit
buds had attained the same stage of deve10pment on
December 9, 1925, as buds of the same variety on December
16, 1926. Plate XX (C,D,E) is a comparison of Elberta
spur buds on slightly different dates in December for
the years 1922, 1923 and 1926. There is very little
difference in the gross deve10pment of these buds.

Fruit buds of five varieties, Late Crawford, Fitzgerald,
Kalamazoo, Elberta and Gold Drop had reached practically
the same stage of development on December 16, 1926, in
the college orchard at East Lansing. These buds are
shown on Plate XXI (A,B,C,D,E). These comparative
studies seem to indicate that fruit buds of several
varieties of peaches, produced on different types of

wood growth, advance rather uniformly in Michigan under

climatic conditions comparable to those of 1926 and 1927.

17.

Winter Injury to Fruit Buds of the Peach.
Samples gathered on and after December 18, 1926,
contained specimens showing various degreesof injury
from low temperatures. On the morning of December 18
the minimum temperature at South Haven was -10°F. On
two occasions in January, temperatures below zero occurred;
-7°F. marked a cold wave on January 15 and 16, and -9°F.
a similar cold wave on January 26 and 27. Several buds
showed injury in the meristematic tissue and pith at the
tip of the woody cylinder and in the peduncle below the
floral parts, which were themselves uninjured. As
observed under the microscope the xylem was discolored
in these specimens, sometimes well down the cylinder or
up into the blossom. Whether this was direct injury or
merely due to diffusion from the injured area cannot be
affirmed. This type of injury is apparently the same as
that described by Chandler (9) for the peach in New York,
and involves essentially the same region of the bud as
that noted by Roberts {Eggefor the sour cherry in Wisconsin.
Many buds thus injured by cold temperature, doubtless,
ultimately produce peaches, as in the case reported by
Chandler, though one injured as much as that shown by
Plate XXXI (0) would probably develop no further.
Comparison of Figures 8 and C in Plate XXXI shows
either (1) if the killing were recent, which is improbable,
the less advanced of the two buds was affected, or (2)

if the killing occurred on December 18, which is probable,

the buds had developed in size between mid December and

18.

mid February. The same inference may be drawn from
Figure (A) of the same plate which shows the killing
of one blossom at a node while the other survived. The
injury below the floral parts seems to be the first
stage of injury, and a slightly lower temperature brings
about killing of the floral parts as well. This is
illustrated by the specimens gathered at East Lansing
on December 24, 1926, which had been exposed to -l4°F.
or four degrees lower than the minimum temperature recorded
at South Haven. Though injured specimens were not
numerous enough in the material examined to warrant
definite conclusions, their appearance suggests that
the tender point may shift from the base of the bud to
the bldssom itself during the course of the winter;
in other words, the blossom may become more tender.
However, this point is far from being established by
this study.

Plate XXXI (A) shows a node of three collateral
buds taken from vigorous wood growth on February 28.
The bud on the left side of the figure is dead while
that on the right is alive. The dead bud was killed
probably on December 18. The size of the dead bud is
assumed to be a fair measure of the size of the bud at
the time of killing. If that be true, there is conclusive
evidence that there was bud advancement between the date

of killing and February 28 when the sample was collected.

19.

The results here presented would seem to indicate that
supposed differences in bud advancement offer no clues
as to the susceptibility of peach buds to winter injury
and killing by low temperatures. It is more probable, as
suggested by Chandler (8) and Askenasy (1) that the
difference in hardiness between buds of different varieties,
buds on the same tree or buds of the same collateral, may
lie in the chemical composition of the buds or in the
density of cell sap in parts of the bud which are most «
susceptible.

Plates XXXII (A,B), and XXXIII (A) show other
instances of killed buds compared with live buds taken
on the same or approximately the same dates. There was
some bud killing on January 15, 1927, at both South Haven
and East Lansing, when the temperature dropped to ~70F.
and ~10°F., respectively. This fact was indicated in the
sectioned material by the karger size of the killed buds

when compared with buds killed in mid-December.

LMPERATURE RECORDS.

For the purposes of this study, temperature records
were secured for both South Haven and East Lansing. These
records were furnished by the United States Weather Bureau
station at East Lansing. Table 1 gives the minimum, maximum,
and monthly mean temperatures at South Haven from.ray l,

1926 to May 1, 1927. Table II presents similar data for

East Lansing. Table III shows the daily maximum temperatures

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23.

DISCUSSION.

This investigation has shown that buds of peach
varieties generally reputed hardy under Michigan con-
ditions are in the same state of advancement at any
given time in autumn, and during the coldest part of
the winter, when bud killing is most frequent in this
state, as the buds of varieties shown by experience to
be tender.

No difference has been found in advancement at
a given time during this same period as between buds on
vigorous shoots and those on spurs.

No attempt was made to determine the degree of
vacuolization suggested by Roberts (25) as a factor in
winter killing of buds. It is conceivable that differences
of this kind could occur, with bud advancement as deter-
mined by size of floral parts, etc., identical. Ex-
planation of varietal differences must lie rather in the
physiology than in the grosser anatomy of the bud.
Certainly, degree of advancement is not a criterion
of varietal differences in hardiness during the period
when bud killing is most common in Michigan; the degree
of advancement apparently is not correlated with
differences in hardiness of buds occupying different
positions on the tree.

Under Michigan conditions, rest period differences

seem of questionable importance. There is little or no

24.

indication that buds withstand freezing better in mid-
December than they do in January. Since freezing is a
recognized means of breaking the rest period, this
period should end in early winter. In fact, experimental
work by Dutton (12) indicates that the rest period ends
by the latter part of December in Michigan. That buds
do not ordinarily advance more rapidly during January
and February is due to the general absence of high
temperatures. The development reported here from
November 15, 1926 to February 15, 1927, at South Haven,
was made with temperature accumuhations (on the day-
degree maximum above 43°F. basis) of 31 in November, 6
in December, 0 in January, and l in February.

There have been reports (5) of changes in relative
varietal hardiness in early spring, Elberta becoming
more hardy with reference to many other varieties, or,
more accurately, it loses hardiness less rapidly. This
fact leads to the inference that spring development of
peach buds in Michigan may be independent alike of stage
of advancement and of rest period influences. Bud killing
in the spring is, however, of less practical importance
because it is less common in this state.

The study here reported, than, affords no indication
that ordinary cultural practices affect the stage of

development of peach buds. It does not prove that

25.

hardiness may not be affected. Counts of dead buds on
shoots and spurs of varying degrees of vigor are not
altogether consistent. Data reported by Gardner,
Marshall and Hootman (14) are rather inconclusive
inasmuch as trees which were pruned in the previous
winter had higher percentages of bud killing than those
which were both pruned and fertilized. It should be
stated, however, that trees which were merely pruned
had greater average shoot length than the others. If
any generalization is to be made, bud injury was
greatest on trees making the most vigorous growth.

On the other hand, an unpublished study of growth
in an Elberta orchard, made by Bradford at Benzonia,
Michigan, showed 51.45 per cent of killed buds on un-
fertilized trees, and 50.05 per cent on fertilized
trees; in other words, there was no difference. Solitary
blossom buds on all kinds of growth averaged 60 per cent
dead (out of 1510); of 717 single buds coupled with leaf
buds (one of each at a node) 46 per cent were dead; and
of 1150 blossom buds which occurred in pairs with a leaf
bud to each pair, 49 per cent were dead. Stated in
another way, the percentages of blossom buds killed on

shoots of different lengths were as follows:

26.

1.0- 9.9 cm. 46.55 % dead.
10.0‘1909 N 54065 ('76 "
20.0-29.9 " 45.78 % "
50.0-39.9 " 47.57 % "
40.0-49.9 " 49.44 % "
50.0-59.9 " 66.95 % w
60.0-69.9 " 47.47 % "

If any difference is indicated by these percentages,
it is in favor of somewhat greater hardiness in buds
on more vigorous growth. It is quite conceivable that
the difference between the results shown by the two
studies may be accounted for as varietal differences,
or as due to freezing at different periods of the
winter. ' I

This study, therefore, should not discourage
further investigation of the possibility of influenc—
ing bud hardiness by cultural practices. It does show
rather definitely that criteria other than the stage
of deve10pment must be used in appraising these
practices, and that cultural practices designed to
affect hardiness through influencing the rest period
offer little promise under Kichigan conditions. Further-
more, since so far as presented to data, these practices
hinge upon delqying the beginning of the rest period
through prolonged autumnal growth, they are likely to make

the tree itself subject to injury from low winter temperature

 

27.

Siflfiflflflf.

1. Fruit bud differentiation in the several
peach varieties studied begins, under Michigan conditions
similar to those of 1926, during the first two weeks in
September.

5 2. Fruit buds of the peach develop rapidly during
the autumn and go into winter in a relatively advanced
stage in which all of the floral parts are well developed.

5. Among the varieties studied, differentiation
occurred at approximately the same time in September;
development was uniform.during the autumn; buds went
into winter in practically the same stage of develOpment,
and developed uniformly during the winter and early
spring until shortly before the blooming period..

4. There is perceptible advancement in peach
buds during the winter months, despite the occurrence
of few daily maximum temperatures above 45°F., which has
been accepted by many investigators as the critical
temperature marking the growth response of plants.

5. Winter hardiness of the fruit buds in the
peach varieties studied is not, apparently, correlated
with grosser development of the buds.

6. When peach buds are injured by low temperatures,
the entire bud may not be killed. In early winter stamens
and pistils are relatively more hardy than the meristematic

and vascular tissue immediately below the pistil.

28.

7. The rest period in fruit buds of the peach,
as grown under Michigan conditions, is very short.

In the material studied, it apparently began after
November 15 and was probably broken by the sub zero
temperatures of December 17 and 18, 1926.

8. Because of the short rest period of peach
buds in Michigan, no practical importance can be
attached to it as influencing orchard practice, other
than its possible relation to fall spraying.

9. Differences in latitude, rainfall, temperature
and other climatic conditions, though small, between
East Lansing and South Haven, seemed to exert no
significant influence on fruit bud development in the
peach.

10. Cultural practices may yet be found to affect
hardiness of peach buds, but the criteria of this effect

must be other than the stage of develOpment of the buds.

‘ ACKNOWLEDGMENTS
The writer wishes to make acknowledgment to all
those who gave assistance during the progress of this
investigation. Particularly is he indebted to Professor
F. 0. Bradford, under whose guidance the work was conducted,

for help and suggestions, translation of literature, and

29.

interpretation of results; to Professor t. C. Dutton
for microphotographs; to Dr. John Crist for help with
the laboratory technique; to Professor V. R. Gardner
and R. E. Harshall for criticising the manuscript;

to B. G. Sitton for collecting bud samples from the
College Orchard; to the Corporation Fruit Farm at
South Haven for the privilege of collecting samples
from their trees; and to D. A. Seeley of the United
States Weather Bureau Station at East Lansing for the

use of temperature records.

lo-

20"

30"

40"

5.-

6.-

80"

90"

100‘

110'.

120“

130‘”

30.

LITERATURE CITED.

Askenasy, E. Ueber die Jahrliche Periode der Knospen.
(1877)

Bailey, I. 3. Autumn Development of Peach Fruit Buds.
Proc. Am. Soc. Hort. Sc. pp. 50-55. (1924)

Bradford, F.C. Fruit Bud Development of the Apple.
Oreg. Agr. Exp. Sta. Bul. 129.(l915)

Bradford, F. C. The Relation of Temperature to
Blossoming in the Apple and the Peach.
Mo. Agr. Exp. Sta. Res. Bul. 53. (1922)

Bradford, F. C. and Cardinell, H. A. Eighty Winters
in Michigan Orchards. Mich. hgr. Exp. Sta. Sp. Bul.
149. (1926)

Brison, F. R. (Verbal report)
Texas A. & M. College.

Chandler, W. H. The Winter Killing of Peach Buds
as Influenced by Previous Treatment. Mo. Agr. Exp.
Sta. Bul. 74. (1907)

Chandler, W. H. The Killing of Plant Tissue by Low
Temperature. no. Agr. EXP. Sta. Res. Bul. 8. (1913)

Chandler, W. H. Some Peculiar Forms of Winter Injury
in New York State During the Winter of 1914-15.
Proc. Am. Soc. Hort. Sc. pp. 18-24. (1919)

Coville, F. V. The Influence of Cold in Stimulating
the Growth of Plants. Journ. Agr. Res. Vol. 20.
pp. 151-160. (1920)

Drinkard, A. W. Fruit Bud Formation and Development.
An. Rept. Va. Agr. Exp. Sta. 1909-10. pp. 159-205.

Dutton, W. C. The Effect of Some Spraying Materials
Upon the Rest Period of Fruit Trees.
Proc. Am. Soc. Hort. Sc. pp. 176-178. (1924)

Duhamel du Monceau, H. L. Physique des Arbres I.
pp. 199-202. Paris (1758)

140‘

150-
160‘

170-

18.-

19.-

200-

210'“

22.-

230-

240'-

25.-

260'.

27.-

280‘

31.

Gardner, V. R., Marshall, B. E. and Hootman, H. D.
Size of Peaches and Size of Crop. Mich. Agr. Exp.
Sta. Sp. Bul. 184. (1928)

Geleznoff (Cited by Askenasy) Moscow. (1851)

Goff, E. 8. Investigation of Flower Buds.
17th An. Rept. his. Agr. Exp. Sta. pp. 275-276. (1900)

Hedrick, U. P. Peaches of New York.
N. Y. Agr. Exp. Ste. (1917)

Howard, W. L. An Experimental Study of the Rest
Period in Plants. Mo. Agr. Exp. Sta. Res. Bul. I. (1910

Johnson, E. S. Moisture Relations of Peach Buds
During Minter and Spring. Ed. Agr. Exp. Sta.
Bul. 255. (1925)

Johnston, S. An Analysis of the Peach Variety
Question in Michigan. Mich. Agr. Exp. Sta. Sp.
Bul. 126. (1924)

Kirby, R. S. and Martin, J. N. A Study of the For-
mation and Development of the Flower Buds of Jonathan
and Crimes Golden in Relation to Different Types of
Soil Management. Proc. Iowa Acad. Sc. 25. pp. 265-89.
(1918)

Lazenby, W. R. The Development of the Buds in Some
of Our Common Orchard Fruits. Proc. Am. Pom. Soc.
(26th Session) (1899)

Morgan, T. M. Studies in the Development of Fruit
Buds. (Unpublished thesis) Cornell Univ. (1902)
Cited by Drinkard.

Munn, M. T. Fruit Bud Formation. (Unpublished thesis)
Each. State College (1912)

Roberts, R. H. The Development and Winter Injury of
Cherry Blossom Buds. Univ. of his. Agr. EXp. Sta.
Res. Bul. 52 (1922)

Tufts, W. P. and Horrow, E. B. Fruit Bud Differentiation
in Deciduous Fruits. Hilgardia I, No. I. (1925)

Weaver, J. E. A Study of the Peach. (Unpublished
thesis) Univ. of Heb. (1910)

Uiggans, C. B. The Influence of Certain Environmental
and Cultural Conditions on Fruit Bud Formation of the
Pear and Apricot. Journ. Agr. Res. Vol. 51, No. 9.
pp. 865-885. (1925)

32

J

g / i
K / (“:3
f x 43.

\/ 2

 

Plate I.

Upper left- Hill's Chili spur, Aug. 16,1926 (South Haven)
Upper right- Hill's Chili spur, Aug. 51, I926 (South Haven)
Center left- Hill' 8 Chili spur, Sept. 15,1926 (South Haven)
Center right- Hill' a Chili spur, Sept. 30,1926 (South Haven)
Lower left- Hill's Chili spur, Oct. 30,1926 (South Haven)
Lower right- Hill' 3 Chilispur, Nov. 15, 1926 (South Haven)

 

 

Plato II.

Upper left- Hill's Chili spur,'Dec. 18,1926 (South Haven)
Upper right- Hill's Chili spur, Jan. 15,1927 (South Haven)
Center left- Hill's Chili spur, Feb. 15, 1927 (South Haven)
Center right- Hill‘s Chili spur, Feb. 28,1927 (South Haven)
Lower left- Hill's Chili epur,Har. 15, 1927 (South Haven)
Lower right- Hill's Chili spur, Mar. 50,1927 (South Haven)

 

Plate III.
Hill's Chili spur, April 15, 1927.

3‘!

SS

 

 

Plate IV .

Hill's Chili vigorous, July 50,1926 (Upper left) (South Haven)
Upper right- Hill's Chili, Aug. 16,1926 (South Haven)

Center left- Hill's Chili, Aug. 61, 1926 (SOuth Haven)

Center right- Hill's Chili, Sept. 15,1926 (SOuth Haven)

Lower left- Hill's Chili, Sept.60,1926 (South Haven)

Lower right- Hill's Chili, Oct. 60,1926 (South Haven)

 

vi
//,4
, :5.)
”sf: (L
. DA V
\ /
\ /

 

Plate VI.

Upper left- Hill's Chili vigorous Her. 16 1927 (South Haven
Upper right- Hill's Chili vigoroug, lar. 30, 1927 (South Havgn)
Lower left- Hill a Chili vigorous, April 15,1927 (South Haven)

39

 

1‘"?
404

Plate VII .
Upper left- Elberta spur, July 50,1926 (South anen)
Upper right- Elberta spur, Aug. 16,1926 (South Haven)
Center left- Elberta spur, Aug. 51,1926 (South Haven)
Center right- Elberta spur, Sept. 15,1926 (South Haven)
Lover left- Elberta spur, Sept. 50,1926 (South Haven)
Lover right- Elberta spur, Oct. 15,1926 (South Haven)

 

 

   

Plate VIII.

Upper left- Elberta spur, Oct. 50, 1926 (South Haven)
Upper right- Elberta spur, Nov. 50, 1926 (South Haven)
center left- Elberta spur, Dec. 18, 1926 (South Haven)
Centerlefghtfilbbettaappur, Feb. 15,1927 (South Haven)
Lower left- Elberta spur, Feb. 28, 1927 (South Haven)
Lover right- Elberta spur, Mar. 15, 1927 (South Haven)

3

\
b r

99'

Plate Ix.
Upper left- Elberta spur, Har. 50 1927 (South Haven)
Upper right- Elberta spur, April 15, 1927 (South Haven)

  
   

[it

‘(l

 

(

W

 

Plato Xe

Upper left- Elberta vigorous, July 50,1926 (South Haven)
Upper right- Elberta vigorous, Sept. 15, 1926 (South Haven)
Center left- Elberta vigorous, Sept. 50,1926 (South Haven)
Center right- Elberta vigorous, Oct. 15, 1926 (South Haven)
Lower left- Elberta vigorous, Oct. 50, 1926 (South Haven)
Lover right- Elberta vigorous, lav. 15, 1926 (South Haven)

HZ

 

 

Plato XI 0

Upper left- Elberta vigorous, Hev. 50, 1926 (South Haven)

Upper right- Elberta vigorous, Dec. 18,1926 (South Haven)
Center left- Elberta vigorous, Jan. 15, 1927 (South Haven)
Center right- Elberta vigorous, Feb. 15, 1927 (South Haven)[hmd
Lower left- Elberta vigorous. Feb. 28, 1927 (South Haven)

Lower right- Elberta vigorous, Feb.28, 1927 (South Haven)

 

Pl‘te XII. ‘

Upper left- Elberta vigorous, Har. 15, 1927 (South Haven)
Lover left- Elberta vigorous, lar. 50, 1927 (South Haven)
Lever right- Elberta vigorous, April 15, 1927 (South Haven)

“Q

 

A (9

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u
c:
a!"

 

\

 

Plate XIII.
Upper left- Hill's Chili spur, Sept. 15, 1926 (South Haven)

Upper right- Elberta spur, Sept. 15, 1926 (South Haven)
Center left- Hill's Chili spur, Oct. 50, 1926 (South Haven)
Center right- Elberta spur, Oct. 50, 1926 (South Haven)
Lower left- Hill's Chili spur, Feb. 15, 1927 (South Haven)
Lower right- Elberta spur, Feb. 15, 1927 (South Haven)

Q5

@3\

J
(its

1 I
(Ev/I / \ €19)»

 

Plate XIV.

Upper left- Hill's Chili spur, Feb. 28, 1927 (South Haven)
Upper right- Elberta spur, Feb. 28, 1927 (South Haven)
Center left- Hill’s Chili spur, Iar. 15, 1927 (South Haven)
Center right- Elberta spur, Her. 15, 1927 (South Haven)
Lover left- Hill's Chili spur, April 15, 1927 (South Haven)
Lover right- Elberta spur, April 15,.1927 (South Haven)

Ht

   

/\

1

Plate XV.

Upper left- 3111'. 011111 vigorous, Sept. 15, 1925 (South Haven)
Upper right- hinlberthili vigorous, Sept. 15, 1926 (South Haven)
Center left- Hill's Chili vigorous, Sept. 50, 1926 (South Haven)
Center right-Elberta vigorous, Sept. 50, 1926 (South Haven)
Lower left- Hill's Chili vigorous. lov. 50, 1926 (South Haven)
Lever right- Elberta vigorous. lov. SO, 1926 (South Haven)

tn

 

Plata XVI.

Upper left- Hill' s Chili vigorous, Jan. 15, 1927 (South Haven)
Upper right- Elberta vigorous, Jan. 15, 1927 (South Haven)
Center left- Hill's Chili vigorous, Feb. 28,1927 (South Haven)
Center right- Elberta vigorous, Feb. 28, 1927 (South Haven)
Lower left- Hill's Chili vigorous, Mar. 50, 1927 (South Haven)
Lower right- Elberta vigorous, Mar. 50, 1927 (South Haven)

(‘0.
H '1

 

Plate XVII. '
Upper left- Hill's Chili vigorous, April 15, 1927 (South Haven)
Upper right- Elberta vigorous, April 15, 1927 (South Haven)

 

Plate XVIII.

Comparison of Development on the Same Dates at South Haven and
East Lansing.

Upper left- Elberta spur, Oct. 15, 1926 (South Haven)

Upper right- Elberta spur, Oct. 15, 1926 (East Lansin )

Center left- Elberta spur, Dec. 18, 1926 (South Haven?

Center right- Elberta spur, Dec. 16, 1926 (East Lansing)

Lower left- Elberta spur, Feb. 15, 1927 (South Haven)

Lower right- Elberta spur, Feb. 24, 1927 (East Lansing)

SQ

\1 7

19A
_ o
\

\

Plate XIX.

Elberta spur buds on Approximately the Same Date in Different
Years.

Upper left- Elberta spur, Dec. 16, 1926 (East Lansing)

Center left- Elberta spur, Dec. 24, 1925 (East Lansing)
Center right- Elberta spur, Dec. 24, 1926 (East Lansing)
Lower left- Elberta spur, Feb. 17, 1925 (East Lansing)

Lover right- Elberta spur, Feb. 24, 1928 (East Lansing)

9)

 

Plate XX.

Varieties at Approximately the Same Date in Different Years.
Upper left- Gold DrOp-vigorous, Dec. 9, 1925 (East Lansing)
Upper right- Gold Drop spur, Dec. 16, 1926 (East Lansing)
Center left- Elberta spur, Dec. 2, 1922 (East Lansing)
Center right- Elberta spur, Dec. 24, 1925 (East Lansing)
Lower left- Elberta spur, Dec. 16, 1926 (East Lansing)

 

Plate XXI.

Five Varieties on the Same Date.

Upper left- Crawford spur, Dec. 16, 1926 (East Lansing)
Upper right, Fitzgerald spur, Dec. 16, 1926 (East Lanai )
Center left- Kalamazoo spur, Dec. 16, 1926 (East Lansin
Center right- Elberta spur, Dec. 16, 1926 (East Lansing?
Lower left- Cold DrOp spur, Dec. 16, 1926 (East Lansing)

(.5

 

 

‘

r My

(Pb
an

 

Plato XXII.

Upper left- South Haven vigorous, Aug. 16,1926 (South Haven)
Upper rov(center)-South Haven vig.,Sept.15,1926 (South Haven)
Upper right- South Haven vigorous, Sept. 50, 1926 (South Haven)
Center left-South Haven spur, Aug. 16,1926 (South Haven)

Center rov(center)-South Haven spur,Sept. 15,1926(South Haven)
Center row(right)- South Haven spur,Hov. 15,1926(South Haven)
Lower left- South Haven spur, Jan. 15, 1927 (South Haven)

Lever rev(center) South Haven spur(dead),Har.15,1927(8outh Haven)
Lover right- South Haven spur, Iar. 15, 1927 (South Haven)

\

 

Plate XXIII.

Upper left- J.H.Hale vigorous, Sept. 15,1926 (South Haven)
Upper right- J.H.Hale vigorous, Sept. 50, 1926 (South Haven)
Center left- J.H.Ha1e shoot, Sept. 15, 1926 (South Haven)
Lower left- J.H.Ha1e spur, Hov. 15, 1926 (South Haven )
Lower right- J.H.Hale spur, Har. 15, 1927 (South Haven)

 

 

Plate HIV 0

Upper left- J.HJHa1e vigorous, Sept. 27, 1926 (East Lansin )
Upper right- J.H.Ha1e vigorous, Nov. 5, 1927 (East Lansing?
Lover left- J.H.Ha1e vigorous, lov. 15, 1926 (East Lansing)
Lover right- J.H.Hale vigorous, Feb. 24, 1928 (East Lansing)

 

( 5%

slate XXV
pper left
U " J.H.Ha
L252: fight- J.H.H:Ie.pur’ Sept. 27 19'
t- J.H.Ha1e aspur, lov. 4319276 (East Lansin
pur, Jan. 14, 1928 Egast Lansing?)
ast Lansin
a)

St

 

O

Q

 

Plate XXVI.

Upper left- Fitzgerald spur, Oct. 15, 1926 (East Lansing)
Upper right- Fitzgerald spur, Dev. 5, 1927 (East Lansing)
Lower left- Fitzgerald spur, Rev. 14, 1926 (East Lansing)
Lover right- Fitzgerald spur, Dec. 16, 1926(East Lansing)

in
...J

Plate XXVII .
Right- Fitzgerald vigorous, lov. 5, 1927 (East Lansing)
Left- Fitzgerald vigorous, Oct. 15, 1926 (East Lansing)

£1.

 

Plate WIII.
Kalamazoo spur, Dec. 16, 1926 (East Lansing)

L0

 

Plate We

Upper left- Elberta shoot, Hov. 5, 1927 (East Lansing)
Upper right- Elberta shoot, Dec. 2, 1922 (East Lansing)
Lower left- Elberta shoot, Dec. 24, 1925 (East Lansing)
Lower right- Elberta shoot, Jan. 15, 1927 (East Lansing)

a?

Platom 0

Upper- Elberta vigorous, Dev. 15, 1927 (East Lansing)
Center- Elberta spur, Dec. 24, 1926 (East Lansing)
Lover- Elberta vigorous, Jan. 15, 1928 (East Lansing)

6!

(.2

 

Pl‘te m1 0
Upper- Elberta vigorous, Feb. 28, 1927 (South Haven)

The fruit bud en the left of this collateral is dead. the
one on the right side is alive.

- Lever left- Elberta spur, Feb. 28, 1927 (South Haven)

Lover right- Elberta vigorous (dead), Feb. 16, 1927 (South Haven)
The shaded portion shows dead tissue at the base of the pistil

1n the vascular area. Other parts of the bud were alive at the
tine of fixation.

w \
x j .
1.17!
I/\

 

Plato mII 0
Left- Elberta spur(ddavd), Dec. 16, 1926 (East Lansing)

Right- Elberta spur (dead), Dec. 24, 1926 (East Lansing)

Temperature Range during the period of Killing:
D06. 17, 1926 **‘k* -100 F811.
Dec. 18, 1926 none -14° Fah.
Dec. 20, 1926 use 58°Fah.

(,2

z, 4.

 

Plate mIII.
Hill's Chili vigorous, Feb. 15, 1927 (South Haven)
Dead bud on the left of the collateral. Live bud on the right.

 

at

Irma

000 0 000

0 00000 0000000 0
Dow

 

Elberta vigorous, April 15, 1927 (South Haven)

Longitudinal section through an anther.

Plate XXXIV .

Plats XXXV.
Bud development in Elberta peach.
Figure 1

Figure
Figure
Figure
Figure
Figure
Figure

2.
3.

Sept. 15,
Oct. 15,
Nov. 15,
Dec. 18,
Feb. 15,
Feb. 28,
”‘1'. 15,

 

1926.
1926.
1926.
1926.
1927.
1927.
1927.

 

 

 

Plate XXXVI.

Spur fruit buds of different varieties on approximately the
same dates.

Figure 8. Elberta spur bud, Dec. 24,1925.

Figure 9. Crawford spur bud, Dec. 16, 1926.

Figure 10. Kalamazoo spur bud, Dec. 16, 1926.

Figure 11. Fitzgerald spur bud, Dec. 16, 1926.

Figure 12. Elberta spur bud, Dec. 16, 1926.

Figure 15. Gold Drop spur bud, Dec. 16, 1926.

 

Plate XXXVII.

'Winter injury in fruit buds of the peach.

Figure 14. Hill's Chili bud Jan. 15,1927. Shows injury to
vascular tissue below floral parts. (Hots double fruit bud.)
Figure 15. Hill's Chili bud Feb. 15,1927. Very slight injury
in bascular tissue below pistil.

Figure 16. 1111's Chili bud Feb. 15,1927. Killing very pre-
nzunced in the floral parts, and only slight in the vascular

t ssue. ‘

Uigure 17. Elberta spur bud Dec. 16,1926, A live bud.

Figure 18. Elberta spur bud Dec. 24,1926. Entire bud killed,
including the peduncle.

Figure 19. South Haven spur bud Jan. 15,1927. A live bud.
Figure 20. Seuth Haven spur bud Jan. 15,1927. A dead bud in
which the killing is largely confined to the floral parts, and
has affected the vascular tissue only to a slight degree.

 

Plate XXXVIII.
Showing winter injury to fruit buds, and winter bud development.

Figure21. Elberta bud Dec.18,1926, showing injury to the
vascular tissue below the pistil.

Figure 22. Elberta bud Dec.18,1926. A live bud.

Figure 25. Elberta bud Feb. 15,1927. Partly killed bud. Pistils
and stamens are alive. Perianth and vascular tissue are killed.
Figure 24. Elberta bud Feb. 15,1927. A live bud.

Figure 25. Elberta bud Feb. 28,1927. One collateral of two fruit
buds and one leaf bud, showing a dead fruit bud on the left and

a live bud on the right. This illustrates bud advancement dur-
ing the winter.

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