(News article for February 8, 2025)

Late winter or early spring, around the time plants begin to put out new growth, is one of the best times of year to fertilize fruit trees. Some species may benefit from one or two additional fertilizer applications between this time and mid-summer, but this first application of the season is probably the most important.

It’s ideal to adjust levels of most nutrients based on what’s already in the soil. If a person is fertilizing a large area of the same type of fruit tree, I suggest that they get a soil test every few years.

When you fertilize trees, avoid placing fertilizer right next to the trunk. Rather, spread fertilizer around the drip line (the edge of the canopy, or where limbs end) and a bit inwards and outwards from there.

If you spend much time looking, you’ll find different recommendations for how much fertilizer to use around fruit trees. Many recommendations are based on the age of the tree, some are based on trunk diameter, and those for commercial orchards are often based on area.

Even for home fruit trees, fertilizing based on area is generally the approach that makes the most sense to me. The size of a tree at a given age can vary a great deal. Fertilizing based on ground area minimizes the chance that you’ll burn roots or have other undesirable effects on the tree.

Overfertilization with nitrogen, specifically, can lead to excessive vegetative (branches and leaves) growth at the expense of fruit production and predispose plants to certain disease and insect issues, such as fire blight - which affects pears, apples, and mayhaws - and aphids (“plant lice”).

A nitrogen rate of 1 pound actual nitrogen per 1000 square feet is acceptable in most cases, for fruit trees and many other types of plants.

There are many fertilizer options, but for simplicity, I’m making recommendations in terms of 10-10-10. If you use fertilizer with a lower nitrogen concentration, you can use a little more. If you use one with a higher nitrogen concentration, use less. For example, you could use 1.3 pounds 8-8-8, 0.75 pound 13-13-13, 0.6 pound calcium nitrate (15-0-0), or 0.3 pound 33-0-0 instead of 1 pound 10-10-10.

Here are amounts (weight and volume) of 10-10-10 for circular areas of different diameters: 2 feet (0.5 ounce = 1 tablespoon), 3 feet (1 ounce = 2 tablespoons), 5 feet (0.2 pound = 0.4 cup), 10 feet (0.8 pound = 1.6 cups), 15 feet (1.8 pound = 3.5 cups), 20 feet (3 pound = 6 cups), and 30 feet (7 pound = 14 cups).

It may occur to you that the area on which the calculation is based won’t exactly equal the area that you fertilize, if you leave unfertilized space around the trunk. However, I feel comfortable that the approximation is good enough.

In contrast to the per-area-based recommendations, some sources suggest rates equivalent to about 0.5 pound 10-10-10 per year of tree age, up to a maximum of 3 to 12 pounds, depending on the type of fruit tree. If you follow this type of guideline, be sure to spread out the fertilizer well to avoid fertilizer burn.

Note that it’s ideal to keep the area under the canopy clear of turfgrass and other weeds, since these compete with trees for nutrients and water.

Let me know if you have questions.

Contact Mary Helen Ferguson.

Young Oriental persimmon tree (Photo by M.H. Ferguson)