Coleus cuttings can be started now

If you have kept a coleus as a houseplant over winter, you can still start cuttings for transplanting to the garden. Use a sharp, clean knife or a pair of pruners to cut the stem just below a leaf node. Remove the lowest leaves, dip the cut end into a rooting hormone and insert it into some fresh, sterile potting soil.

The cuttings will also readily root by placing them in a glass of water. Transplant to a pot with growing medium once a small mass of roots has developed. The plants will be ready to use in the garden by the middle of May when the danger of frost has passed.

Gradually acclimate the coleus plants to the outside environment by increasing the time the plants are left outside over a period of a week or so. Be sure to avoid direct sun at first so the leaves do not burn.

• 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 a south-facing window 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 build up of salts from either fertilizer or a hard water source. Excess salts 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 salts. It will be 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.

• Mid- to late March and early April are generally good times to control insects such as magnolia scale with an application of dormant oil. Verify that you have a problem insect before pursuing any controls and avoid applying treatments just to make sure there will not be insects present.

Temperatures should be at least 40 degrees, with no chance of freezing or rain within the following 24 hours, so the appropriate timing will vary from year to year depending on the weather. Avoid spraying on windy days to prevent any drift of the spray.

As with any product, be sure to read the label to make sure the plants you are treating will not be damaged by the dormant oil spray. Dormant oils can be very effective with minimal impact on the environment when used properly.

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