The Best Way to Prep Aspen Trees for Spring & Summer

The aspen, a relatively small tree, usually grows 30 to 40 feet tall when mature. It thrives in cool weather and brightens the landscape when fall arrives and its leaves turn deep yellow. The tree grows in U.S. Department of Agriculture plant hardiness zones 1 through 6, and can falter in summer's high heat and humidity. When planting a young aspen tree, choose a spot that's protected from hot summer sun, such as near an east- or south-facing wall of a building. This tree also doesn't handle pollution well, and isn't a good choice for a site near a busy street in an urban setting.

The aspen tree needs light, well-drained soil to grow well. If your soil contains clay and tends to hold water and stay soggy for long periods, amend the planting site with sand to improve its drainage. You can also build a mounded area, or berm, about 18 to 24 inches high and plant the tree at its center. The elevation helps the soil drain quickly. An aspen also needs even moisture, especially in spring when it puts out new growth, so give the tree extra water during dry spells. Aim for about 1 inch of water weekly during the growing season.

Feeding a young aspen in spring gets it off to a good start and helps prevent stress to the tree during hot summer weather. Choose a complete, granular formula fertilizer, such as 16-4-8, and apply it at a rate of 2 pounds of nitrogen per 1,000 square feet of area under the tree. As summer heats up, add a 3- to 4-inch layer of organic mulch, such as straw or shredded bark, to keep the aspen tree's roots cool, while also keeping down weeds that compete for soil nutrients.

Aspen trees are subject to several diseases and pests that can begin in spring and continue into summer. These include fungal diseases, such as leaf spot, rust and powdery mildew. You can prevent these problems by watering without wetting the foliage and clearing debris from under the tree regularly. If a fungal disorder becomes severe and causes leaf loss, you can spray with a fungicide that contains chlorothalonil as the active ingredient. This chemical is effective against aspen leaf spot. Follow the label instructions for application. An aspen can also attract aphids, which can cause leaves to brown and curl, but these pests can be controlled by spraying with insecticidal soap, diluted at a rate of 5 tablespoons per gallon.