Within the realm of all gardening chores, scarcely anything fosters more debate than the pruning of roses. To prune, or not to prune, that is the question.
In general, we advise gardeners in the Northeast to wait until spring before taking out the sharp shears to cut back your thorny climbing, shrub and ground-cover roses. The exceptions would be hybrid teas and grandifloras, which may not be hardy in your area. These should be pruned back this fall and then buried under your choice of mulch. Left unpruned and in the open air, they’ll likely die back during the winter.
Another exception would be diseased roses. Examine your roses for stems affected by blackspot, mildew or rust and be rid of these before winter. You’ll also want to rake up any affected rose foliage and be careful not to add these leaves to the compost pile. Either burn them or add them to the next load headed to the transfer station.
The worse offender of the three primary rose diseases is blackspot, Diplocarpon rosae, a fungus that literally develops as black spots on leaves. These progress to black spots fringed with yellow rings on both sides of the leaves. In worst cases, the leaves all go yellow and black and drop off to the ground.
Since is worst during wet, humid weather, this should not have been too bad a year in much of northern New England. Areas of southern New England, however, did have it worse. If you were affected, autumn cleanup is critical. The spores that cause blackspot can over winter in the garden and reappear next year.
If blackspot was a problem for you, plan on applying an organic fungicidal soap and a product known as wettable sulfur, which will keep spores from germinating. Act early next spring; the sulfur must be on plant before the spores arrive when the weather warms into the 70s. Sulfur is water soluble and must be reapplied after every heavy rain.
Other tips to help with blackspot, mildew and rust . . . Water in the morning rather than evening; drip irrigation is best. Make sure you have good air flow around your plants. And, most importantly, purchase roses that are known to be disease resistant. Planting hybrid teas, in most cases, is asking for trouble. Try compost or manure “teas” sprinkled over the foliage. This time-honored solution helps the plants’ own defenses against disease. Ask your garden center for Messenger, a remedy based on plant protein. Members of the American Rose Society have been raving about this new product from California that uses cutting-edge plant science. For years, organic gardeners have been using a solution of 1 teaspoon baking soda in a quart of water, with a few drops of mild dish detergent added into the mixture to act as a “wetting” agent — meaning the soap helps the baking soda stick to the foliage.
Paul Tukey - October 3, 2005.
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