By Jake Overgaard
Extension Educator, Winona County
I know it's exciting in the spring when apple trees are flowering and the trees are covered in blossoms. We naturally want to preserve every single flower and hope that it becomes a perfect apple that we pick and eat straight off the tree. The thought of going out and deliberately removing tiny apples before they really even have a chance is unthinkable to some, but you should think about it.
Thinning fruit can have multiple benefits. First, if you want your trees to produce consistently each year, thinning (and being timely about it) can have real benefits. Thinning can help minimize what is called "biennial bearing", or when a tree produces lots of apples one season and few to none the next. Biennial bearing is especially common in Honeycrisp and Haralson cultivars, among others. Also, by having fewer apples on a tree, fruit size improves and the apples can mature more evenly as well. Trees have limited energy, so fewer apples means there are fewer "mouths to feed". Also, on younger trees and weaker branches, fewer apples can prevent branches from breaking.
So when should you thin apples? First of all, wait until "June drop" has passed (I'll let you guess when that usually occurs). June drop is when a tree naturally sheds some of its fruit, leaving you with fewer apples to thin yourself. Depending on the year, June 20th or so is about the time to start thinning, but a simple rule of thumb is to thin when the apples have the diameter of a dime. Thinning at this time will help to prevent biennial bearing and help maintain the future year's yield. Even if you don't get started at exactly the right time, the current year's production will benefit from your efforts.
Thin apples down to one fruit per cluster (typically there are 5 per cluster) and leave 6 inches in between each apple or roughly a fist length. Also, using this standard will help you determine if you need to thin; the tree may already have a light crop due to frost or other effects, in that case, don't thin. It is possible to thin by hand, simply remove the fruit from the stem. However, you want to be sure that you aren't damaging the tree by tearing off any spurs. A small pruner or even a scissors works pretty well. At first, it may seem like a daunting task, but with a little practice, you can become a speedy thinner. I know some growers who feel terrible when they have to thin (be it an apple, a carrot, or a radish for that matter), but less is more in this case, and your final product will be better. For more information on apple tree maintenance view the archived Yard and Garden News article titled "Simple Steps to Productive Apple Trees" at this address: http://blog-yard-garden-news.extension.umn.edu/2009/05/simple-steps-to-productive-apple-trees.html