For the first time in years, there is cause for celebration in the Sagers' orchard. The fruit trees came through our mild winter with no damage. Trees of all varieties had an abundance of blossoms. They weren't damaged by spring frost. Temperatures were favorable and sunshine was plentiful, so the bees could pollinate them.
This means I can, in good conscience, finally write a column on thinning fruit, since I have enough fruit that I need to thin.
The first question most gardeners ask is, "Why would I want to thin my fruit?"
Several reasons come to mind:
Thinning is essential to increase the size of fruit.
Excessive fruit will ALWAYS reduce fruit size and quality. Removing part of the crop is the most effective way to improve fruit size.
If trees are loaded with blossoms and all the blossoms develop into fruit, the fruit will be small and poor quality. Thinning is particularly important when fruit is crowded in clusters.
As trees age, fruit size tends to decrease.
Trees with poor vigor need more thinning than vigorous trees.
Trees growing on poor soils need help to develop large fruit. Low fertility and poor drainage also affect fruit size.
Thinning keeps trees bearing every year.
Trees will set the fruit buds that will bloom in 2001 by midsummer this year.
Thinning balances the fruit crop for this year with the bud production for next year. Trees produce only so much energy. They can devote the energy to fruit or to buds. If too much energy goes to fruit production this season, they form no blossoms for next year's crop. The trees go into biennial bearing and produce crops every other year. Many apple varieties are prone to this problem.
Young trees often set too many fruits. If they are not thinned, the energy of the tree goes into producing fruit at the expense of producing vegetative growth that will make a strong and viable tree. Remove the fruit from newly planted trees for the first few seasons to prevent this problem.
Thinning also promotes fruit color and quality.
Many varieties have better fruit color and better taste when a heavy crop of fruit is thinned. Separating fruit improves light distribution around the fruit, thus improving fruit color. It also improves pesticide coverage, thereby reducing insect damage.
Thinning prevents tree damage.
A final reason for thinning that will not be readily apparent until later in the season is tree damage. Every year I see many trees with sticks and boards propped under the branches in an effort to keep them from breaking from the weight of the fruit.
Nevertheless, I often see many trees split right down the center when the fruit load gets too heavy. Save the tree by properly thinning the fruit.
The reasons for thinning are apparent, but how and when to thin are more confusing.
Most fruit trees set far more blossoms than are actually needed for a full crop of fruit. Excess fruit must fall because there are simply too many.
The first drop occurs right after blossoming.
Fruit that is not pollinated does not develop and falls to the ground. This distresses many gardeners but is not as serious as it seems.
If all the blossoms developed into fruits, it would severely damage the trees. It takes only 10 percent to 20 percent of the blossoms to develop in heavy bloom years to have a successful fruit harvest.
The second drop is called the June drop. During this drop many of the fruits fall because the tree is trying to regulate its crop. After this drop, it is time do the final thinning by hand to ensure a successful crop.
The earlier you do the thinning, the more significant the influence on fruit size. The later in the season you thin, the less it contributes to increased fruit size. Late hand-thinning can help improve crop quality by grading out culls while they are still on the tree.
Spacing the fruit during thinning is also important. On apples, each bud opens to reveal a flower cluster of five blossoms. The large central blossom is the king with four smaller ones around it.
The king makes the largest apple, and ideally only the kings would set fruit. Even then, many of those would also be thinned, leaving the fruit spaced about every eight inches on the outside perimeter of the tree, where they are exposed to sunlight. Thin pears the same way.
In years without frost and freeze damage, peaches set more fruit than the tree can support. Three to four weeks after bloom, when the largest fruits are the size of a quarter, thin so the remaining peaches are spaced every 8 inches. Fruit thinning allows the remaining fruits to develop to their optimum size, shape and color and prevents depletion and breakage of the tree.
Thinning plums is usually limited to the large, Japanese varieties. Thin them so they are four inches apart.
It is more desirable to have the tree's energy go into growing moderate amounts of large fruit than a large amount of small fruit.
From an economic standpoint, a bushel of large fruit is worth twice what a bushel of small fruit is worth. So don't let too many fruits remain. For the best benefit, complete your thinning within 20 to 25 days after full bloom.
Do not fall prey to the broken tree and little fruit syndrome this year. Get out in the orchard and remove the excess to ensure a good harvest this season.