June drop of fruit in fruit trees

Poor pollination is likely why your fruit trees are dropping small fruit.

Each June, many home fruit growers are amazed and horrified when they find small, undeveloped fruit lying on the ground under their fruit trees. Many MSU Extension hotlines received calls about little-but-perfect fruit falling off for no apparent reason.

To the tree owner, it’s a mystery. To the tree, it’s business as usual. So what’s the reason? Let’s chalk it up to “loneliness.” Many kinds of fruit trees require another similar fruit tree of a different variety to swap pollen with. For example, a Rome apple needs to get pollen from another nearby apple cultivar, like yellow transparent or from a crabapple. Bees and other insects act as the transporters.

Apples must have a transfer of pollen from a different kind of apple or crabapple to develop fruit of picking size. They are called “self-unfruitful” because of this.

Other fruit trees that require an exchange of pollen from the same kind of tree but a different cultivar are pears, sweet or black cherries, Japanese plums and nuts like hickory, filbert and English or Persian walnuts.

But for every rule, there are several exceptions. A few cultivars in this group are self-fruitful like Bartlett pear and Golden Delicious apple.

Other kinds of fruit are considered to be self-fruitful. They do not require another similar tree to produce fruit. All they need is an abundant source of pollinating insects like bees to move the pollen around the tree. The self-fruitful fruit trees are peaches, nectarines, apricots, European plums and tart or pie cherries.

When fruit trees produce flowers, they must be pollinated for fruit to grow. Trees have one goal in mind: They need to produce viable seeds to continue their species. There is a short time after the flowers fade that small fruit, both pollinated and unpollinated, begin to develop. Towards the middle to the end of June it becomes apparent to the tree which fruit have viable seeds developing inside. And those that are duds get unceremoniously dumped. This event has its own clever name of “June drop.”

Fruit might not be pollinated for other reasons, but those are less common. During a cold, wet spring, there may not be enough pollinators flying around when the flowers are blooming. Or, the worst reason could be that the tree owner sprayed the blooming tree and killed the pollinators.

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