Take cuttings of plants to grow over the winter

It is time to take cuttings of annuals such as geraniums and begonias that are to be kept over the winter. Cool nights in late 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 pearlite. 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 will 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 the yellow jackets flying in and out of the nest.

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. Paper wasps will build nests under eaves, signs and fence railings and will sting if disturbed.

These are all beneficial insects so control them only if they pose a safety hazard.

• Espaliered plants can soften large blank spaces on walls or fences when there is minimal bed space.

To train espaliers, young, supple twigs and branches are bent to meet design requirements. Carefully tie the branches in place with raffia or plastic tape. The ties should be secured loosely so the flow of water and nutrients through the tree's stems is not constricted.

Make adjustments to ties during the growing season as necessary. Formal espaliers do need regular attention to keep them looking good and will likely need to be pruned several times over the course of summer.

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