Fruit Tree Thinning Adds Quality Notes Horticulturist

John R. Pyzner  |  10/4/2004 4:23:48 AM

Distributed 03/24/03

Fruit thinning is often an important step in consistently producing good quality fruit. It is a time-consuming task, but it can be very beneficial, especially for peach, plum and apple trees, according to LSU AgCenter horticulturist Dr. John Pyzner.

Fruit trees will often set more fruit than is needed for a full crop. Several undesirable things can happen. Excessive weight from the fruit can cause tree limbs to break. Excessive fruit set often will result in small fruit with poor flavor. Excessive fruit set also can result in alternate bearing in which a tree will produce little or no fruit in the year following a large fruit crop.

Pyzner says fruit thinning is generally most effective when it is done shortly after fruit set. Sometimes, however, fruit thinning a couple of weeks prior to harvest can result in larger fruit and less limb breakage.

The LSU AgCenter horticulturist says although thinning will reduce the amount of fruit being produced, it improves fruit quality, which can bring higher prices. The importance of fruit thinning varies with different types of fruits.

"Fruit thinning is very important on peach trees," Pyzner says, noting that peach trees frequently set an excessive number of fruit. The heavy fruit crop can result in poor quality fruit and damaged trees.

"Fruit thinning should begin as soon as frost danger is over," Pyzner advises, adding, "Most fruit thinning is done by hand, which is very time consuming." Using sticks to break up fruit clusters and shakers to shake fruit off the trees are less time-consuming methods, but they do not produce consistent thinning.

Fruit are generally thinned to 6-inch intervals on twigs. Early peach varieties are usually thinned to 10 inches because of the short time they have for the fruit to mature. When thinning, look at the number of fruit remaining on the tree and not at the ground. Looking at the ground will prevent you from removing enough fruit. Thinning is also a good time to remove damaged fruit. A properly thinned mature peach tree will usually have 700 to 600 fruit remaining.

"It takes fewer large peaches to make a bushel; therefore, the yield can remain good on thinned trees," Pyzner says. For example, he explains that a peach tree producing 2-inch diameter fruit will produce 3.4 bushels of 293 peaches each, for a total of 1,000 fruits. A tree producing 2 1/2-inch diameter fruit yields 4.4 bushels of 159 peaches for a total of 700 fruits. A tree producing 3-inch diameter fruit yields 6.1 bushels of 98 peaches each for a total of 600 fruits.

Japanese plums, which include most plums grown in Louisiana, tend to overbear like peaches, Pyzner says. Fruit on these plums should be spaced 4-6 inches apart, and the fruit cluster should be broken up. Native plums do not need thinning unless heavily loaded.

Apples frequently require thinning. There is usually a natural fruit drop in June. If excessive fruit remains, the apples can be thinned to 6-8 inches along the limbs. Thinning to one apple per fruiting spur can aid disease control.

Pears are usually thinned only when very heavy crops are set and the trees might be damaged. Thinning is usually done a few weeks before harvest.

Oriental persimmons are seldom fruit thinned unless a heavy crop threatens to damage limbs. Sometimes persimmons will fail to produce a fruit crop the year following a heavy crop. Fruit thinning during heavy crop years appears to reduce alternate bearing.

Grapes, muscadines, citrus, figs, blackberries and blueberries are not fruit thinned. Grapes and muscadines are frequently pruned in the winter. This reduces the number of buds available to produce fruit clusters. The pruning results in improved fruit quality and also controls the size of the vines.

Pyzner recommends contacting an extension agent in your parish LSU AgCenter office to learn more about pruning fruit trees. In addition, look for Gardening and Get It Growing links in the Feature section of the LSU AgCenter Web site: www.lsuagcenter.com

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On the Internet: LSU AgCenter: http://www.lsuagcenter.com/
On the Internet: www.louisianalawnandgarden.org.
Source: John Pyzner (318) 644-5865, or Jpyzner@agcenter.lsu.edu 

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