Thinning Peaches: One Fruit Every Six Inches and Why It Matters

The tree sets more than it can ever finish

A healthy peach in a good spring can set five or six times the crop it is able to ripen. The tree has no way of knowing this. It will carry every one of those fruitlets along until they are competing for the same sugar, and the result is a heavy tree covered in fruit the size of a walnut, with a stone taking up most of the middle and almost no flavor.

Thinning is not a refinement. On a peach it is the single job with the largest effect on what you eat, larger than feeding and larger than watering. Fruit size does not increase gradually with the number removed; it jumps once each remaining fruit has enough leaf area to itself. Roughly thirty leaves have to work all season to finish one good peach.

There is a second reason, and it lasts longer than one season. A tree that ripens a huge crop of small fruit sets very few flower buds for the following year, and it snaps its own branches doing it. Peaches thinned properly crop steadily every season; peaches left unthinned swing between a heavy year of poor fruit and a year with almost nothing.

Wait for the natural drop, then thin in two passes

Peaches shed some of their own fruit a few weeks after flowering, once the tree can assess what it has set. Thin before that drop and you remove fruit the tree was going to keep, then watch the tree drop more. Wait until the shedding has clearly stopped and the remaining fruitlets are about the size of a marble, roughly half an inch to three quarters of an inch (1.5 to 2 cm) across.

Do it in two passes rather than one. The first pass is fast and rough: take off everything obviously damaged, misshapen, or growing in a cluster, and get the tree down to somewhere near the target. Two or three weeks later go round again, when the survivors have grown enough to compare, and take it to the final spacing.

The second pass is the one people skip, and it is where the quality comes from. By then it is obvious which fruit is running ahead and which has stalled, and you can keep the best of each pair rather than guessing.

One fruit every six inches, measured along the branch

The working rule is one peach every 6 inches (15 cm) of fruiting shoot. Use your hand: from the tip of your thumb to the tip of your little finger with the hand spread is close enough to six inches for most adults, and it is far quicker than a ruler. Put your thumb on a fruit you are keeping and remove everything within the span.

Where a shoot is short, that can mean a single fruit on the whole shoot, or none at all. That is correct. Where a branch is strong, well lit and carrying plenty of healthy leaf, you can close the spacing slightly to 5 inches (12 cm). On a shaded inner branch, open it out to 8 inches (20 cm), because fruit in shade will not size or sweeten however few of them there are.

1. Take the doubles first Peaches often set in pairs from one bud, and twinned fruit almost always finishes flat-sided and splits. Remove both if there is another good fruit nearby, or keep the larger and rounder one.
2. Take anything marked Scarred, russeted, misshapen or blemished fruitlets never recover. Anything with a weeping bead of gum on it is being fed on from inside; take it off the tree and out of the garden rather than dropping it beneath.
3. Keep the fruit facing outwards Where you have a choice, keep fruit on the outside and the upper side of the branch where it gets sun, and remove fruit hanging into the middle. Color and sugar both come from direct light.
4. Twist, do not pull Hold the shoot steady with one hand and roll the fruitlet off between thumb and finger with a twist. Pulling straight down tears the bark and takes the fruiting spur with it.
5. Step back and count After each branch, stand back and count the fruit you have left. Almost everyone under-thins the first year. If it looks like too few, it is probably about right.
6. Clear what falls Rake up the thinnings and remove them. Fruitlets left lying under the tree are where brown rot and fruit flies overwinter.

Expect to remove somewhere between two thirds and nine tenths of what set. A mature garden peach carrying a good crop holds only a hundred to a hundred and fifty fruit. If you are leaving four hundred, you have a tree of small fruit and a poor year to follow.

Check the branches while you are there

Thinning is also when you find out which branches are going to break. Peach wood is brittle, and a long horizontal shoot carrying eight fruit will split at its base in the last fortnight before picking, when the fruit is heaviest and a summer storm arrives.

Sight along each fruiting branch. Anything already bending noticeably needs either more fruit taken off or a prop underneath: a forked stake or a length of timber padded where it meets the bark. Tying a bending branch up to a higher one works too, as long as you use soft tie and check it is not cutting in a month later.

It costs nothing to thin a doubtful branch harder than the rule suggests. Losing four peaches is trivial; losing the branch costs you three years of crop from that part of the tree.

What to record, and why it pays next year

Write down the date the natural drop finished, the date of each thinning pass, and roughly how many fruit you left on the tree. Then, at harvest, write down what the fruit was actually like: the size, whether it was sweet, whether anything split.

One season of that tells you nothing much. Three seasons of it tells you exactly how hard to thin your tree, in your soil, in your climate, which no general rule can. The pattern that usually emerges is that the year with the fewest fruit recorded produced the best eating, and that is the correction most gardeners need.

Note the branches you propped, too. The same limbs bend every year, and knowing which ones lets you thin them harder in the first pass instead of scrambling for stakes in a gale.