Iris plants should be divided periodically

Bearded iris can be divided and replanted after they have finished blooming. Be sure to discard any shriveled or diseased parts. Be careful not to plant the new sections too deeply.

• Weeds growing between cracks in brickwork or sidewalks are unsightly but easy to eliminate.

Treat them with a nonselective herbicide when they are small to avoid having to pull them out by hand. Avoid spraying on windy days so adjacent good plants are not damaged.

• This is a good time to cut some of your outdoor flowers for indoor display. It is best to cut the flowers during a cool part of the day and to put them in water as quickly as possible. Remove any foliage that will be under the water in the vase.

Keep your arrangements in a cool room out of direct sunlight. Adding a preservative to the water can lengthen the life of the flowers.

• Finding some carpenter ants indoors does not necessarily mean there is a nest in your home. It is important to try to determine whether the ants are coming from an outdoor or an indoor nest, although this can be difficult.

If you find carpenter ants in your home during winter, late winter or early spring, that suggests the ants are coming from a nest in the building. If you see activity later in the year, it is less clear if the nest is in the building.

Black carpenter ants can vary in size from one-quarter to one-half inch in length. They do not eat wood, but they create tunnels in it, leaving telltale sawdust behind. They are attracted to wood that is softened by moisture. They will also nest in rotting trees, stumps and boards left on the ground.

You will likely need to work with a professional exterminator to eliminate an indoor infestation.

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