Layer plants in containers and pull garlic mustard

When planting a container, mix plants of different heights for a layered effect. Try something different from the typical tall plant in the center with a ring of shorter plants and instead include plants that will cascade over the edge.

Think of your containers as large, exuberant floral displays when choosing plants. Combine different sizes of containers in each group for a good effect. A simple design of only one variety of annual planted in each container can also be beautiful.

• Be sure to pull out any garlic mustard that may be flowering in your garden. Hand-pulling garlic mustard is effective as long as the root is removed. This plant has a two-year life cycle. Seeds germinate in early spring, remaining small as basal rosettes for the first year, sometimes carpeting the ground.

Adult plants (second year) can reach up to 4 feet tall and bloom in May through June. Numerous small white flowers will be at the ends of stems and may also be found at points along the stem where leaves are attached. Garlic mustard dies after flowering and the seeds disperse in August when the long, slender seed capsules open at maturity.

This species reproduces readily from the numerous seeds produced. Garlic mustard produces a garlicky odor from all parts of the plant.

• Pinch fall-blooming plants such as chrysanthemums and hardy asters to control their size and increase production of flowers. Pinching will encourage side branching, producing bushier, stockier plants.

Make the first pinch when the plants reach 6 to 8 inches in height by removing approximately 1 inch from the tip of each shoot. When the resulting lateral branches reach 6 inches, pinch them as well. These plants should not be pinched later than July 4 in the Chicago area, as flower buds are formed at this time and late pinching can delay or prevent flowering.

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