Tips for saving your plants from common garden ailments

• Bearded iris can be divided and replanted once they have finished blooming. Be sure to discard any shriveled or diseased parts. Do not 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 the spray does not drift onto nearby plants in your garden. Nonselective herbicides such as glyphosate (Roundup) will damage or kill any plant that is touched by the spray.

• If your hybrid roses have been losing their lower leaves and the remaining leaves have yellowish foliage with dark spots, it is likely you have black spot, a common fungal disease.

• Using an approved fungicide will not cure the parts of the plant that already are infected but can help prevent it from spreading. The fungicide will need to be applied once every 7 to 10 days. Read and follow label directions.

• Be sure to clean up any leaves that have fallen from the plants, because fungus spores on the leaves can spread the infection.

• Many landscape shrub roses do not need to be sprayed, because they have been selected to be resistant to black spot. Do not spray Rosa rugosa, as fungicides can burn the foliage.

• 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.

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