Freeze-thaw cycle can heave plants

Check garden beds to be sure plants have not heaved out of the ground due to freeze-thaw-freeze cycles typical at this time of year.

Gently press the crowns of perennials back into the ground, but avoid compacting the soil by stomping heavily around plants.

Applying a layer of mulch will help prevent additional frost heaving as the weather transitions from winter to spring.

• March is a good month 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 do not apply treatments just to make sure there will not be insects present.

Temperatures should be at least 40 degrees during the application, with no chance of freezing or rain within the following 24 hours. 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.

• Prune fruit trees and grapes when the worst of the winter cold is past and spring growth has not yet begun.

• 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 in the garden to acclimate them. 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 days are still cool.

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