Cuttings prepped now will be ready for spring planting

It’s officially spring, which means I’m starting to think about what to plant in the garden.

Coleus is one of my favorite annuals; I have several pots currently growing on windowsills in the basement.

If you 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. You can also place cuttings in a glass of water to prompt them to root. Once a small mass of roots has developed, transplant the coleus to a pot with a growing medium. The plants will be ready to use in the garden by the middle of May when the danger of frost is past.

You can also cut back your coleus if they have gotten leggy due to low winter light levels and plant them out in the garden when the weather permits. 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 don’t burn.

Houseplant maintenance

Spring is also a good time for houseplant maintenance. Prune houseplants as needed and start fertilizing them as they begin new growth.

Rotate your houseplants every week or two so that each side receives an even amount of light for more uniform growth and a balanced shape.

As the sun strengthens, some plants, like African violets, may need to be moved away from a south-facing window to avoid leaf scorch.

Take some time to remove any spent flowers, dead leaves or branches and any yellowing leaves. You might also need to remove dust from the leaves with a kitchen sprayer, or by gently wiping them off with a moist cloth. It’s a good time to repot houseplants if needed. Take note of any white or yellowish crust near the drain holes of the pot or at the base of the pot; this indicates a buildup of salts from either fertilizer or a hard water source. Excess salts in the growing medium can damage plants — you might see this in brown leaf tips and margins. Flush out the soil with a thorough drenching of water to get rid of the salts. It’s best to do this outside or in the sink since there will be a large amount of water coming out of the drainage holes.

Insect patrol

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 with an insect before you take action, and avoid applying treatments just to prevent insects.

Temperatures should be at least 40 degrees Fahrenheit with no chance of freezing temperatures 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 it. Dormant oil 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.