Warm days of spring awaken earnest gardeners

The beginning of spring has crept up on me quickly this year. A couple of unusually warm days provided a great opportunity to clean and organize the garage so I would be ready to go once busy gardening season arrives.

Take a walk around your garden to check on any new plantings of pots in No. 1 or smaller containers from last year to make sure they have not heaved out of the ground due to the freeze-thaw cycles typical at this time of year. Gently press the crowns of perennials or small shrubs 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. Spring planning for your plants also applies to those houseplants in apartments.

Insect control

March is a good month to control insects such as magnolia scale with an application of dormant oil. Before you begin using any treatment, be sure that you have an insect problem. Avoid applying treatments as a preventive measure. To ensure spraying is effective, temperatures should be predicted to be at least 40 degrees Fahrenheit with no chance of freezing or rain within the coming 48 hours in the Chicago area and 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 dormant oil spray. Dormant oil can be very effective with minimal impact on the environment when used properly.

Prune now

Now that the worst of the winter cold has passed and spring growth has not yet begun, it is also time to prune fruit trees and grapes.

Gardeners, start your seeds

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 seedlings into a “growing-on” mix in slightly larger containers when they have two sets of true leaves. Gradually introduce 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 will be stunted in cold weather, so it is best to wait to plant them until the end of May.

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