Thin Crowded Fruit Now, For a Lot of Good Reasons Beyond the Garden Basics Podcast

If you’re looking to harvest bigger pieces of fruit from your trees and vines this summer, now's the time to get out your hand pruners and thin off the overcrowded fruit. Other good reasons for thinning lots of little fruit from trees now can also thwart bigger problems later this year, such as undersized fruit, excessive fruit drop, and broken fruit tree branches.
Here are some tips for thinning from the fruit tree experts at UCANR:
• For apples, European and Asian pears, apricots, peaches, nectarines, plums, pluots, kiwifruits, and persimmons: Remove some of the fruit. Space fruit evenly along each branch, with perhaps six inches between each piece of fruit. More importantly, be sure to leave the largest sized fruits on the tree or vine. Although the trees might appreciate a light feeding now, the best time to fertilize these crops is in July and August, when the trees are setting their fruit buds for the following year. An exception would be peach and nectarine trees attempting to recover from peach leaf curl. For those varieties, thinning and fertilizing now can help redirect the tree’s energy into producing more leaves to replace the fallen ones.
• For table grapes, remove grape bunches so that there is at least six inches of space between each remaining bunch of table grapes. Cut off the "tails" from the remaining bunches at that same time. This is the lower one-quarter to one third of the bunch, where it begins to taper down in size. This will send more energy to the remaining grapes on the bunch. The book, "The California Master Gardener Handbook" advises that fertilizer can be applied for each grapevine when the berries are about a quarter-inch big, usually in May. The same book advises gardeners to apply about 50 gallons of water per week per vine, during the hottest months (June through August) here in the Central Valley. Apply less (about 35 gallons a week) during May and September. Adding a few inches of mulch to the top of the soil beneath the vines will help preserve soil moisture.
• Because of their small size, cherries are not usually thinned from backyard trees. In addition, nut crops, such as almonds and walnuts, are not thinned.
• What about blueberries? The amount of thinning will depend upon the blueberry variety and fruit load relative to the vegetative area of the plant. Larger plants and branches that are more vigorous can support a heavier fruit load.
• Citrus trees tend to thin themselves, a phenomenon called “June Drop.” However, citrus fruit thinning now can help a tree drop fewer fruit in late spring.
Certain citrus types such as Valencia oranges or some mandarins have tendencies towards alternate bearing. That’s a year with heavy fruit production followed by a year with sparse production. You can reduce the potential of a tree to alternate bear by reducing the fruit load in a heavy fruit set year by thinning out some of the fruit. Pruning the tree will also help to offset alternate bearing. Also, fertilize less in light years and more in heavy years so that the trees needs are met according to the demands of the fruit load. Despite using these strategies, some varieties will just alternate bear.
• Do not allow the old citrus fruit to stay on the tree longer than necessary. This may contribute to a smaller crop and perhaps, more fruit drop, for the next crop. And, as you may have noticed, those oranges and mandarins that usually produce ripe fruit in the winter but still have some left on the branches may taste dry, with little or no flavor. Cleaning up fall fruit now beneath citrus trees can help cut down on future pest and disease issues, as well.
The University of California’s “California Backyard Orchard” website goes into the science of the benefits of thinning deciduous fruits:
Removal of flowers or young, immature fruits early in the spring can lead to increases in fruit size by limiting the number of fruits that continue growing to harvest. It increases the