As perennials emerge in spring, some may need to be divided

It is best to divide most perennials in the spring when they are showing a couple inches of growth.

When dividing a plant, choose the strongest-looking parts of the plant and discard the rest.

Plants that bloom in April and May can also be divided after they bloom. A sharp, flat garden spade works best for this job.

• Install supports for perennials that require staking in early spring as the plants begin to grow. It is best to install support systems before the plants actually need support and let them grow up through your support system.

• It is time to plant cool-season annuals that can tolerate a light frost — such as pansies and primulas — to add color to your garden. These annuals can be used as under plantings to bulbs to complement their flowers and carry color over until summer annuals are planted in mid- to late May.

Choose plants that are well developed with lots of flowers and buds, as these early spring annuals do not have much time to develop after planting.

• Install bare root plant materials as soon as you can after they arrive in the mail. Unpack plants and make sure the packing around the roots is moist. Store the plants in a cool place that will not freeze until they can be planted.

It is a good idea to soak the roots of trees and shrubs in water for a short period of time before planting. Do not let the roots dry out.

Prune only broken branches and roots before planting. There is no need to prune to compensate for transplant shock.

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