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Bearing fruit: taking care of apple trees

June 11, 2009
By Stephanie Bethke-DeJaegher

I have lost a few things in my perennial borders this year, but there is something that even though, apparently, the winter weather was tough, our apple trees were not affected.

They are so full of teeny tiny apples this year it is almost amazing to me.

So, this year, we are being a little more aggressive when it comes to a few things that we will be doing at our house to ensure that our apples are the best. Here, in part is some of the things that we will be doing as suggested by Emily Tepe who is a Research Fellow at the U of M.

Do you have a couple of apple trees in your yard that just aren't producing much fruit? Do you get a lot of apples each year, but they're smaller than you would expect?

Thankfully there are some simple things you can do to improve yields and increase fruit size.

There are a few things to understand about the behavior of an apple tree. Most apple trees, when left to their own devices, only produce a large amount of fruit every other year. In other words, they are naturally biennial. We can change that to a large extent through fruit thinning. Thinning involves removing excess fruit to allow space for remaining fruit to grow large, and to allow flower initiation and development for the following year.

Thinning also promotes improved fruit uniformity, color, flavor, and reduces limb stress and breakage.

So when is the best time to thin? This is the tricky part. There is a short window during which you should thin an apple tree, which falls between fruit set and flower initiation.

Fruit set occurs after the petals have fallen off, and the remaining ovary begins to swell.

That's pretty simple. But if we can't see the flowers, how do we know when initiation happens?

Thankfully, flower initiation is dictated by day length, which is quite reliable, and generally occurs around June 20 in this region.

Fruit thinning should be done before then or next year's harvest will be compromised. A good rule of thumb is to thin the tree when the fruits are about 1?2 inch in diameter, or about the size of a dime.

Most apple trees will self-regulate to a small degree, meaning they will drop some fruit to reduce the burden. This is called the June drop period, and in this time the tree will naturally abscise some of the tiny fruit.

Abscised fruit is recognized by a yellow pedicel - the stem that connects the fruit to the tree.

These fruits become loosely attached and can be removed with a flick of the finger. June drop may happen before or after the ideal thinning window, so don't rely on it as a guide. Just remember the 1?2-inch rule.

How much should we thin? If you look closely, you'll see that each bud produces a cluster of about five flowers. The first and largest flower in each cluster is called the "king bloom" and it will go on to produce the "king fruit," the largest fruit in the cluster. Ideally, this is the one to keep, but it can sometimes be difficult to determine when the fruits are so small.

Generally, fruit should be thinned to a spacing of about 6 inches. This may seem excessive when looking at those tiny apples, but consider when they grow to 3 inches or so how close together they'll really be. And that is when they'll need a lot of light to mature, and will be weighing down the branches.

A spacing of 6 inches will allow the tree to produce large, uniform fruit while conserving some energy to work on flower buds for next year.

So how exactly do we thin the fruit? Thin by carefully plucking the tiny fruits off the ends of their pedicels (stems). This prevents any injury to the spur which is holding next year's buds. You can use a thinning shears to make this a little easier. Just snip the fruit off right at the top.

One note of caution: Haralson apples are very prone to biennial fruiting. If you have a Haralson tree and you want it to produce fruit every year, you may have to thin so excessively that you get only a small crop.

In this case it may be best to permit its biennial nature and get a large crop every other year."

Good luck with your apple trees this year.

For more gardening information, you can reach me at



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