You may have noticed that at certain times during the growing season, local grape farmers “drop crop.” That means they are thinning out excess fruit clusters. This improves the quality of the remaining grapes by lowering the stress on the vines as they try to ripen too much fruit.
The same improvement in quality happens when you thin fruit from peaches, nectarines, apricots, Asian pears, plums, and apples. Most other fruit trees don’t require thinning. But the five types of fruit listed above are notorious for setting too much fruit, especially peaches, nectarines, and Japanese plums.
If you are thinking about planting fruit trees in your garden or landscape, consider dwarf varieties. They make thinning a cinch, since the fruit is within easy reach. Even semi-dwarf varieties can reach 15 feet or more, which means you have to go high up on a ladder to reach the top. Or, you can top them when they’re dormant to keep them low. But if you’re going to all that bother, why not just plant dwarfs? In fact, tests show that you get more fruit per square foot of land devoted to fruit trees from dwarfs than from semi-dwarfs or full-sized trees.
So why should we thin fruit trees?
Think of a fruit tree as a workhorse. Work it too hard and you’ll injure it. If it has to bear too large a crop, chances are that it will bear poorly or not at all the next year. And the quality of the overburdened tree’s fruit will be lessened. The tree only has so many leaves, and leaves produce the sugars stored in the fruit. So reducing the amount of fruit means more leaf area per fruit. Thus the more moderate the crop, the better and sweeter the fruit. Overcropped trees also produce small, runty fruits, and thinning improves the size and color of individual fruits.
A heavy fruit set that isn’t thinned can overload limbs and even break them, and that’s just disastrous. You’re not going to need poles to prop up limbs if the trees are properly thinned.
I just came in from thinning my “Snow Queen” nectarine. I used my fingers, especially my thumbnail, to nick through the peduncle — the short stem that attaches the fruit to the limb. Be careful, because by trying to pull small, hard fruits off the limbs, it’s easy to tear back into the bark. Cut rather than pull. I also use a pair of Joyce Chen kitchen scissors to get at fruit that’s tightly clustered. That’s about all the equipment you need, unless you need a ladder to get to the high-rise fruit.
So when should you thin? When fruit has set and swelled to a half-inch or one inch. June is last call for thinning for improved size and flavor, although you can drop crop to lighten the load on tree limbs in July or August.
Now let’s look at the ways to thin the various types of trees that need it.
Apple blossoms appear in clusters, followed by clusters of small apples. The largest, most central blossom is called the king bloom and its fruit has the best chance of making a good sized apple. Apple trees will drop some crop on their own if the load is great, but you want to remove all the apples from a cluster except one — the king bloom. Go along each limb, leaving 6 to 8 inches of space between apples.