Houseplants need attention in spring, too

Prune houseplants as needed and start fertilizing them as they begin new growth. Rotate your houseplants so that each side receives an even amount of light for more uniform growth and a balanced shape. As the sun strengthens, some plants, such as African violets, may need to be moved away from south-facing windows to avoid leaf scorch.

Make a focused effort to remove any spent flowers, dead leaves or branches, and any yellowing leaves. Remove the dust from the leaves with a kitchen sprayer or by gently wiping them off with a moist cloth. This is a good time to repot them if needed.

A white or yellowish crust near the drain holes of the pot or at the base of the pot indicates a buildup of salt from either fertilizer or a hard water source. Excess salt in the growing medium can damage plants. The damage symptoms include brown leaf tips and margins. Flush out the soil with a thorough drenching of water to get rid of the salt. It is best to do this outside or in the sink, as there will be a large amount of water coming out of the drainage holes of the pot.

• Start seeds of warm-season annuals and vegetables in a moist, soilless seed mix. These seeds should be started six to eight weeks before the last spring frost date, which is May 15 at the Chicago Botanic Garden. Adjust your start dates accordingly if frost-free dates are earlier or later where you live.

Transplant tiny seedlings into a "growing on" mix in slightly larger containers when they have two sets of true leaves. Gradually introduce the small plants to outdoor conditions before planting them in the garden to acclimate the plants to outdoor conditions. They can be planted in containers or garden beds after the danger of frost has passed. Tomatoes do not like cold weather at all, so it is best to plant at a later date if the spring weather is cool.

• Most evergreens will not respond well to being aggressively cut back. A good rule of thumb is to avoid cutting beyond green foliage. Yews will respond to a more drastic cut back into old wood, but be patient, as it may take two to three years to completely fill back in. Consider how long you are willing to wait for the shrub to look good again or do a more gradual reduction of the plant over a few years until you reach your goal. Complete this pruning before the new growth begins in early spring for best results.

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