Let the pruning begin: New growth is vigorous this year
It’s time to begin summer pruning in your gardens — pruning is one of my favorite gardening tasks.
I have seen a lot of shrubs growing vigorously this year. It’s important to prune them to keep them in the proper scale for your garden. New growth mostly stops by early July, so pruning now is the right time.
I’d recommend using 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.
Cicada netting not needed
Remove any netting put on trees to protect them from cicadas. If you find broken tips of branches lying on the ground, this damage was likely caused by the cicadas’ egg laying.
The amount of visible damage to trees has continued to increase, but most of the damage I see isn’t something to be concerned about.
Hybrid roses and black spot
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.
More garden maintenance
Bearded iris can be divided and replanted after they have finished blooming. Discard any shriveled or diseased parts. Be careful not to plant the new sections too deeply.
Prune espaliered plants as they produce new growth to keep them looking crisp. You should expect to trim the espaliered plants several times over the summer to maintain the best appearance.
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 you don’t damage plants nearby. You can also use a weed whip to remove these weeds.
• Tim Johnson is director of horticulture at Chicago Botanic Garden, chicagobotanic.org.