Fruit Thinning

William D. Adams, Extension Horticulturist, ret'd

Thinning is one of the most difficult tasks for most home gardeners to face. They often plant radishes, and every seed seems to come up twice. Then, when the radishes don’t form normal size roots, they wonder what happened. It is important to thin radishes to one inch apart within a week of germination if you expect to have good size roots, and it is also important to thin developing fruit, like peaches, plums, apples, etc., as soon as possible.

Excess fruit create smaller sized yields

Fruit could probably best be thinned at blooming, but since there’s no real practical way to do that yet, at least with stone fruits like peaches and plums, it just about has to be a hand thing. Developing fruit should really be removed when it is less than the size of a dime, and spaced so that the peaches, for example, are 6 to 8 inches apart. If you leave too much fruit on the trees, you may damage them, and you are bound to have smaller fruit. It takes 191 peaches that are 1-3/4 inches in diameter to make a half-bushel, but it takes only 79 peaches are 2-1/2 inches in diameter to make the same half-bushel.

The earlier you can thin the better, so start as soon as you can -- even if the tree hasn’t completely finished blooming. If you only have a few trees in the back yard, it’s easy enough to remove them by hand -- just give them a little twist, and off they come. Commercial growers go a step further and tie an 18- to 24-inch length of rope or rubber hose on the end of a broom handle, and knock the fruit off with this device. There is usually some natural drop of fruit later on in the year, whether you have thinned or not, but even with this, it is important to do the preliminary hand thinning.

It is also important to begin spraying fruit trees if you haven’t already. As soon as three-quarters of the blooms have dropped off, begin to put on cover sprays of an approved insecticide plus an approved fungicide. Regular applications of these pesticides early in the season will guarantee that you will have high quality fruit, free of the fungus brown rot and plum curculio. These unfortunately are common when fruit trees aren’t sprayed. As long as you follow label recommendations, you will find that the end product is still very safe to eat.

At the Harris County Extension Center, we have evaluated low-toxicity management techniques in our small orchard. We used a standard spray program, and had the fruit analyzed for residue at maturity. The levels of insecticides and fungicides were negligible or couldn’t even be found, even with spraying. So, as long as you don’t abuse the right to use pesticides and you are careful to use them safely, as per label directions, you can expect good quality fruit. We use extremely low-toxicity chemicals like sulfur for a fungicide, and insecticidal soaps if insects become a problem.