Pruning Lilacs and Rhododendrons | Real Solutions for the Garden
Photo/Art by Denise Torres Every spring I remove the faded blossoms on our lilacs and rhododendrons after they’ve finished flowering, to help them bloom better the following year. Now the plants are getting too tall to see the flowers well. What do you recommend for pruning lilacs and rhododendrons? — E.W., Boylston, MA
Removing spent flowers — called “deadheading” — is a good idea for many plants, including lilacs, rhododendrons, and mountain laurel. Not only does it keep them tidy, but it also lets the plant devote its energies to producing new growth and flower buds rather than to developing seed.
Pruning lilacs and rhododendrons right after they finish blooming is best when they grow too big for us to enjoy their flowers. Cutting them back removes the old flowers and also lowers the tops for a better view. Do it in late spring to allow plenty of time for new shoots to grow and for next year’s flower buds to form. Pruning lilacs that have grown too large for your area may be done over several years, cutting back a third to half of the stems each year.
I had gorgeous hollyhocks for years, but this year a half-inch bug took up residence in the double ones, beginning with the leaves. What should I do next spring? — Sister A.C., Lake Ronkonkoma, NY
A number of insects can damage hollyhocks: among them, the hollyhock sawfly, the red-banded leafroller moth, the four-lined plant bug, and the tarnished plant bug. The larval stage may be controllable with Bacillus thuringiensis (BT), a bacterium that produces systemic insecticidal toxins. Other organic controls include insecticidal soap or horticultural oil, but these work only in contact with the insect. If you choose to use chemical controls, ask at your local garden center about specific brands of systemic and contact insecticides labeled for these types of bugs. All of these treatments should be applied when the insects first appear. For safety, always follow the directions on the package.
Before using any insecticide, try to identify the insect that’s causing the problem. Bring samples of the insect and its damage to your local garden center; experts there can probably identify or recommend how to best manage your needs. A good Web source on hollyhock insects comes from the Connecticut Agricultural Experiment Station. Go to ct.gov/caes and click on “Plant Pest Handbook” in the left-hand panel.
Suggestions, please, on pruning and mulching gooseberry bushes. — W.B., Willow Street, PA
Gooseberry (Ribes grossularia) is an underutilized and very productive fruiting plant, well suited to the home garden. Thorny, winter-hardy to Zone 3, and low-maintenance, gooseberry cultivars are easy to grow in almost any soil as multistem shrubs or single-stem plants.