THINNING OF APPLES, PEACHES, AND PLUMS 
C. W. ELLENWOOD and PAUL THAYER 
Ohio Agricultural Experiment Station 
Sacrificing So Large a Percentage of the Fruit Which a Tree Has Set Appals 
the Amateur Grower But Experiment Has Proven the Advantages Gained 
(Editor’s Note: — This article is reprinted from a Monthly Bulletin of the Ohio A gricultural Experiment Station, inasmuch as it 
presents indubitable proof of the results of this operation in the shape of records of experiments) . 
B HEN fruit is still too heavily set after the “June drop” 
one can follow the old-fashioned method of using 
braces to support the trees, or thin the fruit sufficiently 
to prevent the limbs breaking. Thinning has several 
advantages over the brace method. It increases the average 
size of the fruit, and to some extent improves its color and thus 
indirectly has a beneficial effect on the keeping qualities of 
apples — because well-colored apples keep better in storage than 
under-colored apples. Thinning is one of the orchard opera- 
tions concerning which no set rule dan be given either as to the 
degree required nor just when or how the work should be done. 
In some years it becomes a. difficult problem for the. orchardist 
while in other years the “June drop” removes just about the 
right quantity. 
Results of experiments at the Ohio Station indicate that the 
best time to thin apples is between four and eight weeks after 
full bloom. The early-maturingvarieties should be thinned first. 
Just how much effect thinning has on correcting the biennial- 
bearing habits of certain varieties has not been determined, but 
it would seem that the early thinning four to six weeks after 
full bloom would have more effect on this factor than later 
thinning. 
Grape shears with rounded points can be used to good ad- 
vantage in thinning, as a workman can work a little faster with 
the shears than with thumb and finger. But in using the shears 
there is a little danger that the fruit on the lower limbs may be 
bruised by the fruit falling from higher in the tree. This is not 
serious with the later varieties, but Transparent may be seriously 
bruised by the falling apples, 
especially if the thinning is 
done rather late. When the 
work is done by using the 
thumb and finger the work- 
man can with a little addi- 
tional effort throw the apples 
clear of the lower limbs. Some 
varieties have a tendency to 
grow in clusters and it re- 
quires a little skill so to thin 
such varieties that the entire 
cluster will not break off in the 
act of thinning. The work 
should never be done carelessly, and rubber-soled shoes should 
be worn by those in the trees. 
T HE number of apples that should be removed from a tree 
depends upon the quantity of fruit remaining after the “June 
drop” and to some extent upon the variety. Some trees bear 
heavily on one side of the tree in alternate years and thinning 
will in such cases balance up the load of the tree and prevent 
splitting. As a general rule, apples should remain from six to 
eight inches apart when the thinning is done. 
From careful estimates made at this Station it is apparent that 
an Apple tree will often produce sufficient bloom for twenty 
times the number of apples that it could possibly mature. 
Fortunately, nature takes care of most of the thinning, but in 
many cases one fourth to one half of the apples remaining six 
to eight weeks after full bloom may be removed with no ap- 
preciable loss in quantity, and with gain in quality. The table 
appended gives results typical of experiments conducted in 
thinning. These records were taken from crops produced by 
single trees in a year when the fruit set rather heavily. The 
picking dates were: Baldwin, October 16; Ben Davis, Novem- 
ber 2; and Oldenburg, August 8. 
T HE thinning of peaches and plums is in some ways much 
simpler than thinning apples. The trees are usually smaller, 
for one thing, so that one can reach every part from a stepladder; 
then, too, the surplus fruits may be snapped off with the fingers 
instead of using shears. 
Although plums are seldom thinned, there are often sea- 
sons when thinning would be highly profitable. The two chief 
reasons for thinning plums are to keep the trees from breaking 
and to lessen the danger of loss from rot. When rot starts in a 
heavily loaded Lombard tree where the plums on the bent limbs 
are literally piled in masses, it is almost impossible to check the 
decay. With proper thinning the upper limbs would not be 
weighted down upon the lower ones, and light and air, as well as- 
spray, could reach each fruit and help to keep it sound. 
The thinning of peaches is a more generally accepted hor- 
ticultural practice. The Peach tree, when not interfered with 
by winter freezes or spring frosts, produces a wealth of bloom 
and almost every blossom sets fruit. If allowed to mature 
these will either break down the tree or, owing to the drain on its 
vitality, the fruit will be small and bring a lower price on the 
market. After the fruits have shed their shucks and are the 
size of small hazelnuts the sur- 
plus ones can be removed at a 
rapid rate by one who has 
had a little experience. The 
peaches are snapped off, leav- 
ing the thinned fruit from six 
to eight inches apart. 
In thinning a long shoot it 
is grasped just above the first 
peach by the thumb and fore- 
finger and the hand is passed 
up the branch about six or 
eight inches, snapping off the 
peaches in passing. A peach 
is then allowed to pass and another six or eight inches 
of branch stripped bare of fruit. With a little experience 
one can remove from 1,000 to 1,500 peaches from each of 
ten or a dozen loaded trees in a day, and leave the remaining 
peaches properly spaced. When the thinning is done by the 
owner the danger usually lies in leaving too many peaches rather 
than in removing too many! 
The season for thinning peaches is in June and usually ter- 
minates with the hardening of the pits about the first of July. 
The hardening of the pits is associated with the formation of the 
seed and as this is particularly exhausting on the strength and 
vitality of the tree, thinning after this period does not seem to be 
of much benefit. The yield of fruit is nearly the same on a well- 
thinned tree as on an overloaded tree, the difference being that 
in one case the greater bulk is flesh and in the other it is stone 
and seed. 
RECORD OF APPLE-THINNING TEST 
OVER 3 
INCHES 
2 \ IN. 
TO 3 IN. 
2 \ IN. 
TO 
2 j IN. 
2 IN. TO 
2 \ IN. 
UNDER 
2 
INCHES 
Per cent 
Per cent 
Per cent 
Per cent 
Per cent 
8.3 
81 8 
78 
2.0 
. 1 
6.8 
84.4 
76 
1 .0 
1-5 
68 g 
19 3 
8.1 
2.2 
24.2 
66.2 
•6.6 
1.7 
3 
l6.6 
59-3 
13 9 
9.2 
I .0 
.6 
43 3 
25.8 
22.3 
8.0 
31 1 
65 4 
i .8 
1-5 
2 
26. 5 
72 1 
.8 
• 5 
1 
93 
68 8 
II 7 
8 7 
1 5 
Baldwin. .. 
Baldwin. . . 
Baldwin. . . 
Ben Davis. 
Ben Davis. 
Ben Davis. 
Oldenburg. 
Oldenburg. 
Oldenburg. 
DATE 
THINNED 
June 16 
July 18 
L'nthinned 
June 22 
July 20 
Untninned 
June 7 
July, i 
Unthinned 
NO. OF 
APPLES 
REMOVED 
4.727 
2,908 
3,568 
3,221 
2.332 
2,248 
NO. OF 
APPLES 
HAR- 
VESTED 
5 402 
4.244 
6,365 
4.259 
4.104 
6,614 
2,8o8 
1,322 
3,542 
325 
