Thinning fruit trees is a simple task and is done for three good reasons:
- lightens the fruit load which protects branches from breaking
- removes competing fruit which results in fewer, but larger fruit at maturity
- removes flawed fruit which results in a more uniform and select crop at maturity
Thinning your fruit trees also gives you an opportunity to observe each tree closely, which helps to spot and treat early threats to the developing fruit. Tent caterpillars, for example, are easy to see when thinning fruit, and easier to eradicate when the invasion is found early.
Although thinning fruit can proceed throughout the summer, the best time to thin fruit is shortly after the young fruit appear. Removing the extra small fruit in late spring allows the tree to direct its energy to the remaining fruit throughout the summer. If you let the fruit get too large before thinning, then the energy the tree has spent on the thinned fruit will have been wasted.
How to Know if a Tree Needs to be Thinned
After a fruit tree has finished blooming, by mid-spring for most species, the small fruit begin to form from successfully pollinated florets. Take a close look and see if the clustered florets are producing small bulbous fruit. Some years a tree will produce lightly and only one or two small fruit appear per bloom cluster. But more often, in a healthy orchard, several small fruit will appear per cluster.
In the picture above, there are 5 young apples in a cluster. If your tree is producing this much fruit, it needs to be thinned. Even with clusters of only 2 fruit, thinning is usually a benefit to the tree. With the fruit cluster above, 4 of these young fruit will be removed, leaving the largest single young fruit to develop.
How to Thin a Fruit Tree
Once you have determined that your tree needs pruning, start from one side of the tree and work systematically to pluck off the excess fruit. Leave the largest, healthiest looking specimen, sometimes called the “King’s fruit”. To remove the extra fruit, care must be taken to not damage the branch spur holding the remaining fruit. Grasp the small fruit between your fingers and pull the fruit backwards so the stem snaps cleanly off at its base. You can let the plucked fruit fall to the ground beneath the tree, or save it in a bucket for the compost bin.
When you’re done, there should be just a single apple per cluster and it will look like this:
As you thin each cluster, keep your eye out for any flaws in the fruit, such as spots, bug damage or poor conformation. These are the first ones you should remove.
If you have two similar sized fruit on a cluster and can’t decide which to remove, take the one which has less sun exposure. This is usually the fruit on the underside of the leaves. You want to keep the fruit which will have the best exposure to sun and airflow.
Now that you’ve learned how to thin a fruit cluster, the final step is to determine how many clusters to keep per branch. In some cases, when a tree is producing a lot of fruit, some clusters are thinned of all fruit. As a general rule, there should be about 4” – 5” between fruit on a branch. Commercial growers often increase this span to as much as 8” – 10”. In our orchard, which is not commercial, I use my fist as a measure for minimum distance between fruit on any branch.
When you are finished, the branches will look like this:
Note the single apple per cluster and the generous spacing between ripening fruit. These remaining fruit are the best specimens of the spring fruit set, and will ripen to be of consistent size and quality which makes it easier to pick, grade and process the harvested fruit in the fall.