Testing garden soil helps you select right fertilizer

Have your garden soil tested to determine how best to manage it and what fertilizers to use. Make a composite sample from a few areas in the bed and send the sample in for testing. If your garden is large, it is a good idea to test several zones.

Soils in the Chicago region tend to have adequate phosphorus levels, so it is usually best to choose fertilizers that do not have phosphorus in them or very small amounts. A soil test can confirm the status of your garden soil.

• Wait to cut back perennials until early spring so that there will be some winter interest in the garden. Some perennials, such as hosta, do not look good after being frozen, so it is best to cut them back in fall as they flatten to the ground.

Use a general rule of cutting back the plants that do not look good late in the fall and the remaining plants in early spring.

• You may want to consider cutting more perennials back in the fall if you have had problems with voles. Voles are compact rodents that can be mistaken for mice. They have stocky bodies, short legs and short tails.

Voles do not hibernate and are active throughout the year, mostly at dawn and dusk. Voles primarily eat the stems and leaves of various grasses, but they also consume other vegetation. They eat the bark of trees and shrubs during the winter.

Gardens with low-lying landscaping, such as arborvitae, spreading yews, junipers and cranberry cotoneaster, have higher potential for vole activity. Voles are most prolific when they have abundant vegetation and cover. The damage is likely to be more severe during extended cold spells with deep snow cover.

Eliminate weeds and dense ground cover around lawns to make these areas less able to support voles. Mow lawns and other turf regularly, and cut back vegetation from the bases of trees and shrubs as winter approaches in areas where there is vole activity.

Also, it is a good idea to pull mulch back away from the base of trees and shrubs and keep the snow cleared away from the base of young trees. Reducing cover makes voles more vulnerable to predators such as hawks and owls. In general, removal of cover is very effective in preventing vole damage.

• Tim Johnson is director of horticulture at Chicago Botanic Garden, chicagobotanic.org.