Controlling insects, propogating houseplants and starting seeds

I have been walking around my garden to look things over and have not found any problems yet. March is generally a good month to control insects such as magnolia scale with an application of dormant oil. Fortunately, I have not had to deal with many insect problems at home over the years of gardening.

Verify that you have a problem with an insect before pursuing any controls. Do not apply treatments just to make sure you will not have insects. Temperatures should be at least 40 degrees Fahrenheit 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 oil sprays can be very effective with minimal impact on the environment when used properly.

This is a good time to propagate houseplants. Softwood cuttings, leaf cuttings, air-layering, cane cuttings, or division may all be done in spring.

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 and will have stunted growth if conditions are too cold, so plant them later if the spring tends to be cool.

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