Fruit thinning is one of the most difficult jobs for homeowners to do when producing tree fruit. After all, you've put a lot of expense and hard work into into producing a healthy, productive tree. The last thing you probably want to hear is that you should knock most of the young fruit onto the ground. However, there are important reasons for thinning fruit crops.
- The most important reason to thin fruit is to increase fruit size.
- Another significant reason is to prevent overbearing. When there is a heavy crop in one year, there may be almost no crop in the second year.
- A third reason to thin fruit is to reduce limb breakage. If too much fruit is left, its weight may break the tree's limbus when the fruit begins to size.
Most deciduous fruit trees benefit from fruit thinning. Apples, pears, Asian pears, apricots, plums, peaches, kiwi and persimmons all respond positively to fruit thinning. Cherries and nut trees are usually not thinned.
Why do many fruits benefit from thinning?
Thinning balances the amount of fruit left on trees with the leaf surface that provides the energy to grow and ripen fruit. Leaving too much fruit on a tree creates a burden for the tree. It takes energy from other processes that occur during the period of fruit development.
One of those processes is fruit bud development for the coming crop. When too much fruit is left on a tree, fruit bud production will be limited. The result is a light crop the following year. Also, when too many fruit are left on a tree, the competition among fruit for scarce nutrients will limit the size of each fruit.
Learning how much fruit to remove will take some practice.
Each fruit type requires a slightly different method.
Apples and pears
When working with apples, Asian pears and European pears, first thin to one fruit per spur. The spur is the short, woody structure from which flowers arise.
You should end up with only one fruit for about every 6 inches of branch. If your tree is healthy and vigorous, it will have more than one spur every 6 inches along a branch. Thus, you will need to leave some spurs with no fruit on them. This helps to balance your crop for next year.
When choosing which fruit to leave, look for the largest fruit. Fruit that is small or damaged should be dropped first.
Thin fruit as early as possible — before each apple reaches the size of a dime in diameter. This usually occurs within the first 20 days after petal fall. Removing these small fruit early will keep energy available for the fruit that remain and for fruit bud development for next year.
Homeowners typically thin by hand. Be careful not to break off the spurs while thinning. Spurs will produce flowers and fruit for many years if not broken during thinning and harvesting.
Apricots, peaches, nectarines and plums
On apricots, peaches, nectarines and plums, you will notice that fruit is borne mostly on one-year-old wood rather than on spurs.
Plums are borne on both one-year-old wood and on small spurlike structures. When thinning these trees, try to leave about 6 to 8 inches between young fruit on the branch. Young fruit should be thinned within 30 days of the end of bloom.
Be advised that peaches, nectarines, cherries and plums naturally drop some fruit near early June. This is referred to as June drop, and it is the tree's way of lightening the crop load.
You may want to leave a little more fruit than you want for the final crop to see which fruit the tree intends to drop for you. With time you will learn how to adjust for the June drop.
Some peach growers use sticks or plastic pipe to knock branches and speed up thinning. If you have just a few trees, I recommend staying with hand thinning. It will be more accurate at leaving the proper amount of fruit per branch.
As the fruit matures and branches begin to bow from the weight, you may need to take more fruit off each limb. This will protect your tree from limb breakage, especially when the tree is young. If you do not want to thin more fruit, you may need to use poles or props to hold up the limbs.
Dwarf fruit trees
When raising dwarf fruit trees, remember to thin a little extra fruit after bloom. These trees are not as strong structurally as a semidwarf or standard tree.
Dwarf fruit trees are precocious, meaning that they tend to bloom and set heavier fruit crops at an early age. Protect their young branches from being overloaded for the first few years.
Importance of pruning
A good pruning job helps to maintain a healthy tree. Pruning removes wood that contributes to overfruiting. Pruning is the first stage of fruit thinning. Without proper pruning, fruit thinning is not a feasible practice.