The Apple Club Newsletter, Summer 2006, Page 1

I am often asked by people who call in July or early August: "What are all the little apples doing on the ground". This phenomenon is called the June drop, though in Ireland, thanks to our cooler climate, it generally happens in July.
As you may know, each year apple trees carry many more flowers than they need to produce fruit, probably in case of a bad frost or other traumatic event that might happen once in a decade, when extra flowers would be of benefit.
Now what usually happens is that, during flowering, many of the flowers get pollinated by insects, but some do not. Usually, within a few days, the first apple pollinated on a particular branch begins growing strongly, stealing all the trees energy at that particular location, and weakening its nearby neighbours, so that after a week or so, the tree gives up on the weak fruits, and allows them to fall off. Typically, this process removes about eight out of ten fruits, but because it happens when they are still tiny, just at the end of flowering, it just looks as though the blossom is just falling off, and being replaced by a smaller number of fruits.
The apples that are left after this initial drop are called set, though they may not make it all the way to harvest. This is because there are often still two or three times as many fruit on the tree as it can bring to fruition. Well trees are very good at sensing how many apples they are carrying, and can selectively abort fruits till the correct number remain.
The way trees sense how many apples they are carrying is via their plant hormones. As young fruits grow on the tree, inside them little seeds are growing and these little seeds release hormones. The more seeds in a particular apple, the more hormones produced on the tree, and also; the more apples on the tree, the more hormone produced. By the end of June, if the tree is carrying a lot of fruit, it senses the high hormone levels produced by the many seeds in all the apples, and it reaches a tipping point, where in the period of about ten days, it drops the weakest remaining fruits, which may sometimes account for up to half the apples that are on the tree. And very cleverly, it drops the weakest fruits. This is achieved because the weakest fruits are the ones with the least number of seeds; perhaps only one or two seeds in each. All along, these fruits have been producing less hormone, and thus have been attracting less reserves from the mother tree, and so by the end of June they are considerably behind the strong fruits, which might carry five or more seeds. So, when the tree comes to deciding which fruits to drop, it makes sense to drop the ones with least seeds, as these are the ones which give it the least change of reproducing, and that, of course, is why the tree produces apples in the first place. And thus, the June drop occurs, and when people look at the orchard, they see this multitude of little apples on the orchard floor, and wonder what has happened. And we tell them, "oh, that's the apple trees getting rid of the fruit they don't want because there are so few seeds in them, and apple trees don't want to waste energy growing apples that don't have many seeds, because the only reason they produce an apple is to produce the seeds that the apple contains". So that's the short answer to the question at the beginning, about all the little apples on the ground, unless you want to know about the apples that we deliberately knock off the trees, but that's another story altogether.

Newsletter Summer 2006		page 1 of 4

June Drop