Why Are My Apples Falling Off?

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This is the time of year that is both disappointing and exhilarating for any fruit grower because of the phenomenon called “June drop”.  It is disappointing because of what you thought would be your best apple crop and your dreams of apple crisps and pies galore… suddenly begins to drop off the tree.  But it’s okay because as a fruit grower, you know that most fruit trees will produce many more blooms than are actually needed by the tree to produce a full fruit load.


June Drop apples on ground
"June Drop" apples on ground beneath the tree


An apple tree in full bloom, will produce 10-15 times more flowers than needed for a healthy tree fruit load; consequently, the excess flowers, if left untouched, creates the branch breaking fruit load potential of 10-15 times more fruit than the tree can safely produce!  This means that 90-95% of the fruits must fall off to avoid overloading the tree.  If the apples don’t fall off, you’ll need to hand thin them anyway, just to make sure the remaining apples will size up properly.  The exhilaration comes from knowing that what is left on the tree, if cared for correctly, will be your apple crop for this year!


A full load of apples on the tree
A full load of apples on the tree


In order to bear fruit, the trees must first produce flowers, those flowers in turn, must be pollinated and the ovaries fertilized for fruit to form and grow.  Plants have one major function... that is to produce viable seeds to continue their species.  In fruit trees, for a short period of time after the flowers fade, both fertilized and unfertilized ovaries (fruits) begin to develop.  Typically, within a couple of weeks, the totally unfertilized ovaries, which are about the size of large peas, will drop off.


Relative size of unfertilized apple ready to drop off (Note yellow pedicel)
Relative size of unfertilized apple ready to drop off (Note yellow pedicel)


Bear in mind that for any fruit, the developing fertilized seeds regulate and control the expansion and development of the ovary flesh around the seeds; specifically, that yummy flesh, which we commonly call “fruit”, is meant to provide nutrients to the seeds when they break their dormancy and begin to grow.  Some partially pollinated and fertilized ovaries will continue to develop on the tree.  Even though the fruit is often malformed and may have just a few viable seeds due to inadequate pollination, it still hangs there on the tree.


Cross section of malformed apple
On Left- Cross section of partially fertilized apple (Note lack of 2 missing seeds) On Right- Fully fertilized apple developing normally


In apples and pears, when young fruits are about 0.5 to 1 inch in diameter, another or second fruit drop occurs, usually towards the middle to end of June; consequently, it is given the moniker of “June drop” by fruit aficionados.  Fruit dropping this time of year is considered to be a direct result of competition among young, developing fruits.  Research conducted by Cornell University at Geneva, NY indicated “fruit that can maintain a continuously high growth rate, stay on the tree.  However, fruit that have a slow growth or slow their growth for several days will drop.”


Comparative size of apples as part of June Drop
Comparative size of apples going into the time for "June Drop"


Yes, it is a type of survival of the fittest fruits with only the best, strongest and most perfect fruits with all of their seeds developing, will remain on the tree.  Well, why not survival of the fittest fruit?  After all, who wants to sink their teeth into dinky, deformed fruit?  This natural thinning process will remove some of the excess fruit, allowing the remaining fruit to develop properly.  Watching fruit fall off the tree can be unsettling; especially, when you were thinking about all the pies you were going to make at harvest.  Even though the numbers of fruits falling off due to this natural thinning process may initially seem too high, additional hand thinning for tree health is often necessary.


Size comparison of developed and underdeveloped apples
Relative size comparison of developed and underdeveloped apples


This additional hand thinning of fruit will ensure that the fruit remaining on the tree will size up properly and will not negatively affect tree health.  Leaving too many fruits on (overcropping) a tree, can damage the tree.  In fact, overcropping on young trees, and choosing to do nothing because you have been looking forward to a bumper crop for years, is not a good combination.  If that young tree is not strong enough or doesn’t have sufficient resources for its own health and growth, then encounters multiple periods of high heat and drought stress… it may drop ALL of the apples!  And then the only pie you end up eating at harvest time might be… HUMBLE PIE!


Cross section of a June Drop apple
Cross section of a June Drop apple (Note flesh thickness differential on the side with no developing seeds)