Dakota Gardener: Thinning apples for improved quality

Carrie Knutson, Horticulture Agent
North Dakota State University Extension
Thinning fruit on apple trees will help spread out the tree’s energy resources and prevent broken branches.

I planted my apple trees about four years ago. One of the apple trees is very productive. It is the little tree that could, despite being my dog’s third favorite chew toy (the dogwood and lilac shrubs are No. 1 and 2).

Judging by the number of blooms, the tree has big dreams for this growing season. The apple blossoms escaped the frost in May. If the bees were able to do their jobs, there will be an extra-large apple crop. Sadly, the apple tree’s structure is not up to supporting all the weight of those apples, so I will be thinning apples this year.

Thinning fruit on apple trees will help spread out the tree’s energy resources, resulting in larger fruit with better quality. Reducing the number of fruits on a tree also frees up energy that can be used to produce flower buds for next year which minimizes biennial fruiting. This is the main reason fruit is thinned from trees.

In addition, fruit thinning will reduce the risk of broken branches from the weight of too many apples later in the growing season. This is important for young trees with weak branches, but it is equally important for older trees that have huge crops of apples. However, proper pruning will help reduce branch breakage on older trees more than fruit thinning.

To thin apples, remove them from the tree before they are the size of a dime. Leave the largest fruit, removing fruit that is small or damaged first. For apple trees, leave one or two fruits per flower cluster or thin fruits to about one fruit every 4 to 6 inches. It may take some practice to figure what is the best balance for your tree.

Don’t forget, Mother Nature will often aid in our fruit thinning actions. Some fruit will drop from the tree without any help from us. Remember to account for this loss when you do your thinning.

Sometimes thinning isn’t necessary because a late frost or poor pollination results in a smaller number of fruits. Dry weather and high winds can also cause fruit to drop. Last year, there was not enough apples to even worry about thinning fruits on my tree.

Thinning by hand is the most common method for gardeners. Be careful not to tear or damage the young branches. A small scissors is a great tool to use for fruit thinning.

Chemicals can be used to thin fruits but are often only used in orchards. Chemical thinning can be unpredictable and many factors can determine the results.

Fortunately, my tree is still short enough that I can reach the top branches with the help of a step ladder, and hand thinning will not take me that long. Happy gardening!