Make Your Peaches Larger by Thinning Enough

Readers nectarine tree

Q. My 23 year old nectarine is always loaded with fruit. I sent you a picture. I usually "thin" out the fruit when they're quite small but I can't seem to thin out enough so they get bigger. Should I remove the flowers now before the fruit forms or wait until the fruit is formed and then attempt to thin out? I know the tree in the picture is ugly but the fruit it bears is delicious.

A. I am not concerned with the looks of the tree but I am concerned that it has enough canopy to shade the branches which helps prevent sunburn on the limbs and fruit. Sunburn damage on limbs in turn attracts boring insects and increases the decline of the tree.

            Since the leaves are responsible for collecting solar energy and converting this solar energy into chemical energy in the form of sugars, the number of leaves compared to the number of fruit is a pretty critical relationship if you want larger fruit. You want anywhere around 50 to 70 healthy leaves for every good-sized fruit.

Peach before thinning

            I know you won't go around counting the leaves to determine the number of fruit to remove but it gives you an idea that if you don't have a good canopy of leaves, then you will have to remove a lot of fruit.

            This is why it is important for your tree to have good canopy development from proper pruning. This allows sunlight to penetrate on to leaves inside the canopy. Leaves growing in shade produce fewer sugars and may actually rob sugars from developing fruit.

Peach after thinning

            This is why we tell people to leave fruit spaced an average of about 4 to 6 inches apart on the fruit-bearing limbs. Start removing fruit when they are the size of your thumbnail.

            I would not remove flowers as an alternative to thinning the fruit. You don't know which flowers are going to set fruit and which ones will not. You might leave flowers that don't set any fruit.

            Harvest your fruit when they are still firm but have developed their full-color. It is acceptable that there is just a little bit of green left on the fruit at the time of harvest. Depends on the variety.

            This helps avoid a lot of bird damage to the fruit. The birds like to get them when the sugar content is starting to climb. Following Murphy’s Law, this is nearly always the day before you decide to pick them. Pick soft fruit at the first sign of bird damage and let undamaged fruit ripen on the kitchen counter for a couple of days. After they ripen, put them in the refrigerator to help preserve their freshness.