When trees are rich with fruit, thinning can improve the harvest

Friday, June 29, 2018 9:33 PM

Editor’s note: Get Growing, written by the La Plata County Extension Office’s Master Gardener Program, appears during the growing season. It features timely tips and suggestions for your garden and landscape.By Eric Ryba

For those of you with fruit trees, this year is turning out to be the opposite of last year’s total lack of tree fruit.

Many of you may have noticed your fruit trees (apples in particular) shedding lots of small fruit. Do not be alarmed, this is the “June drop.” Fruit trees generate far more blossoms than they can support as mature fruit. The June drop is nature’s way of thinning the crop. Trees will shed fruit that are poorly pollinated, which then allows the trees limited energy to be used to mature the remaining fruit.

Even with the June drop complete, it is often necessary to further thin fruit to improve the crop and maintain the health of the tree. Overloaded trees will produce smaller fruit of lower quality and are more susceptible to certain pests and disease.

Plums, peaches and apples commonly set fruit in such abundance that the weight of the maturing fruit can tear branches from the tree. Thinning takes time and a little practice, but if your goal is to produce high-quality fruit, it is worth the effort.

Plums often set in large clusters so remove enough to leave about 2 inches between fruit. Peaches are best thinned in two phases, the first when the fruit is no larger than a grape to a spacing of about 4 inches and then again when walnut-sized to a spacing of 8 to 10 inches.

Yes, it is emotionally painful to tear a perfectly good looking, young peach from a tree, but the remaining fruit, when fully ripe, will provide the ultimate reward. Apples should be thinned to one fruit per cluster and a spacing of 4 to 6 inches. For apples being pressed into cider, size and appearance are not critical, so thinning may not be necessary other than to potentially prevent branch damage.

It is also common to see additional apples drop mid-summer, often because of codling moth larva (caterpillars) in the immature fruit. A practiced eye can see affected apples on the tree. These apples should all be removed and disposed of to prevent the larva from maturing to adult moths.

Eric Ryba has been a Colorado master gardener since 2014. He lives in La Plata County.