Question: The “Diamond Princess” semi-dwarf peach tree that I planted in 2011 has started bearing fruit this year, but the 700 peaches that have already fallen to the ground in the past two weeks are only golf-ball sized or ping-pong ball sized and none of them are peach-colored. They are yellow/green. I've taken a few bites from them without ill effects. They don't taste bad, but they don't taste good either. I know I should prune the tree (I have never pruned it, nor used insecticide), but will pruning solve this problem and allow the peaches to ripen?

Answer: You are not alone in your frustration with growing peaches. Some years are banner years for peach production, while others have nary a fruit in sight. However, there are several things you can do to improve your chances of growing a good peach crop in future years.

One of the biggest factors influencing peach production is the weather; late spring frosts in particular. Since many varieties of peaches are early bloomers, their flowers are sometimes blasted by late spring frosts. When this happens, the blossoms or young fruit will drop from the tree very early in the season. This was not the case with your tree, however, because the fruit did not begin to drop until much later in the season.

Another factor that often affects peach production is a lack of pollination. With many of our bee species in decline, adequate orchard pollination has become more and more problematic for many gardeners. Signs of poor pollination on a peach tree include very early fruit drop (when the peaches are barely the size of your pinky fingernail) or no fruit production at all. Since most peaches are self-fertile, there's no need to have cross-pollination partners, but without bees, the pollen will not be transferred from the male flower part to the female. But, again, I don't think this was the case with your tree either.

I believe there is another factor at play with your “Diamond Princess” peach tree, and it's one that, unfortunately, could have been prevented.

Fruit trees that produce an abundance of fruits (called overbearing) are almost always subject to the fruit drop you've experienced. Seven hundred peaches is far more than any young tree can support, let alone one that's producing fruit for the very first time. It seems that your tree was overzealous in its production, and once the fruits became too much for the tree to bear (quite literally!), it shed that fruit in an attempt to protect its energy and food stores for future growth. Bearing fruit is stressful, and your tree's natural reaction to all that stress was to drop all of the fruits.

It's the job of the fruit grower to limit the over-production of fruits through a process called thinning. In the future, when your peaches are about the size of a nickel, thin them so that only one fruit remains on every 5 to 6 inches of stem. This will allow the remaining fruits to grow larger and reach full maturity. To thin, simply pick off “extra” fruits with your fingers or use a clean pair of pruners to carefully snip them from the plant.

If fruit trees are not thinned and allowed to carry a full load of fruit, often a crop will not occur at all the following season, simply because the tree can't sustain repeated heavy production. This means that an unthinned fruit tree will often bear biennially, producing lots of fruit one year and none the following. Because of this, don't be surprised if your tree bears minimal fruit next year.

From now on, be sure to properly thin the fruits. And not only does thinning improve the size and quality of the fruit, it also improves air circulation around the developing fruits, cutting down on the prevalence of fungal diseases such as brown rot and peach scab.

Horticulturist Jessica Walliser co-hosts “The Organic Gardeners” at 7 a.m. Sundays on KDKA Radio with Doug Oster. She is the author of several gardening books, including “Attracting Beneficial Bugs to Your Garden: A Natural Approach to Pest Control” and “Good Bug, Bad Bug.” Her website is jessicawalliser.com.

Send your gardening or landscaping questions to tribliving@tribweb.com or The Good Earth, 622 Cabin Hill Drive, Greensburg, PA 15601.

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