Beware of fungal disease on roses

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

Begin a spray program with approved fungicides immediately. The fungicides need to be applied once every seven to 10 days, as they work to prevent the disease and do not cure what is already infected. Be sure to clean up any leaves that have fallen from the plants.

Many landscape shrub roses are resistant to black spot and do not need to be on a spray program. Do not spray Rosa rugosa, as the fungicides used to control black spot can burn the foliage.

• 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.

• Shrubs have put on a lot of growth this year so far. Prune them as needed to keep them in the proper scale for your yard. Growth will be mostly hardened off in early July, so there should be minimal new growth when pruned at this time.

Use a pair of hand pruners instead of an electric hedge clipper to create a more natural look by making individual cuts at different heights throughout the shrubs. For a more formal look, make cuts at the same height.

Prune right above the leaves to help hide the cuts. Careful pruning will leave the plants smaller but not looking "sheared."

Remove dead wood as necessary.

• Keep pruning your espaliered plants as they send out new growth to keep them looking crisp. You should expect to trim the espaliered plants several more times over the course of the remaining summer to maintain the best appearance.

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