Time to prepare for next spring's plantings

It is time to take cuttings of annuals such as geraniums and begonias that are to be kept over the winter. Cool nights in September will harden off the plants, which will make them more difficult to root.

Take a tip cutting 2 to 3 inches long and stick it in a well-drained potting medium such as one part peat moss and one part perlite. Keep the cuttings in humidity and bright light.

Cover the cuttings with a plastic bag and ventilate daily by opening and resealing the bag. Once they are well rooted, typically in two to four weeks, transplant to a 2- to 4-inch pot filled with a growing medium. The size of the new pot should depend on the vigor of the rooted cuttings.

• Populations of yellow jackets (a yellow-bodied social wasp) build up in summer. They are unwelcome visitors to picnics and are particularly attracted to sweet things like soda. Practicing good sanitation is the best way to minimize any pest problems.

Yellow jackets tend to make their nests in the ground or in stone walls, so watch these areas as you are working in the garden. When the weather is warm during the day, there will be a lot of activity with yellow jackets flying in and out of their nests.

Bald-faced hornets construct large paper nests in trees and large shrubs at head height and above, so you should be aware as you are working in the garden. Recently, I saw a bald-faced hornet's nest attached to a garage wall between vines growing on a trellis about 5 feet above the ground.

Paper wasps build nests under eaves, signs and fence railings and will sting if disturbed. These are beneficial insects, so control them only if they pose a safety hazard.

• Crabgrass may be evident in your lawn now, especially if it has been neglected or in areas along driveways or walks that are compacted from foot and vehicle traffic.

This annual weedy grass has a wide leaf blade that is light green and seeds readily in the fall. Pull it out by hand if that is feasible to prevent seed formation. It is difficult to mow it low enough to remove any seed.

There are herbicides that will control crabgrass, but they are not as effective after the crabgrass has set seed. These herbicides are most effective when the plants are young and actively growing, but tend to be difficult to identify unless you look closely.

Make note of bad areas in your lawn and apply a pre-emergent herbicide (one that prevents weed seeds from germinating) in early spring before lilacs flower.

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