Revive your container gardens with a shot of fertilizer

If the plants growing in your containers or baskets are looking stunted or have leaves that are yellowing, they may need supplemental fertilizer.

The frequent watering required for containers and baskets can leach nutrients out of the growing medium. Use a liquid fertilizer as needed to perk them up.

It is best to fertilize the containers and baskets when the plants are moist and not dry. Fertilizing plants that are very dry can result in damage to the plants' roots.

Annuals growing in garden beds may also need some supplemental fertilizer, although overwatering can also cause the annuals to be stunted with yellowing foliage.

• It is important to identify the insects on any plants before treating with an insecticide to determine whether or not the insect really is a problem. If it is, then try to assess whether the damage being done warrants control.

The presence of insects feeding on the plants should not warrant automatic treatment. Some insects are beneficial and help control other insects naturally.

If an identified pest is causing significant damage, it is important to use a correct control with proper timing. If a variety of treatments are available, use the least toxic control possible.

• Continue to groom your perennials and annuals by removing yellowing foliage and spent flowers. Make note of perennials that have flopped and need staking so that a support system can be installed next spring before the plants actually need it.

Gentle pruning of more vigorous perennials can help keep your border from looking overgrown. Cutting leaves off at the base can reduce the size of the plants without having them look pruned.

You may want to let certain dried flowers on plants, such as astilbes and coneflowers, to remain standing for fall and winter interest. Goldfinches visit my coneflowers in fall and eat the seeds.

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