Regional Growing Guide: New England
New England's erratic winter and spring temperatures, which might shift more than 50 degrees from one day to the next, can exact their toll on roses. Savvy gardeners winterize their plants by covering them with mulch, then wrapping them in woven mulch cloth or burlap to protect from both the cold and drying winds. The wraps come off in spring, and by June, the roses are in full bloom. Intense heat during July and August may slow down the plants, but they will bounce back with renewed vigor in September. Many of the most successful roses are new landscape roses and floribundas that are cold hardy and resist black spot and mildew.
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Now that the growing season has begun, we're enjoying our gardens, especially our lovely roses. Some shrubs require minimal care, but roses need a regular maintenance program for peak performance all summer long.
Fertilizer
You can use a controlled-release fertilizer, which is the simplest to use and requires only one or two applications for the season. If you use a water-soluble fertiizer (20-20-20), it is recommended that you fertilize once a month. Each plant is given about one gallon of this solution throughout the summer. You can also supplement in between these applications with an organic fertilizer consisting of equal amounts of alfalfa, cottonseed, bone, and fish meal. Two cups of this mixture is worked into the soil around the perimeter of each plant and watered in well. Because roses have lots of feeder roots just below the soil surface, it's important to cultivate with care.
Mulching
Mulch benefits rose plants in several ways. We suggest organic mulch because it contributes valuable nutrients to the soil as it breaks down over the season. It also provides a blanket of protection from hot summer sun, slows water evaporation, and discourages weeds. And, if weeds do sprout in organic mulch, they're easy to pull because the roots tend to grow in the loose mulch material rather than anchoring themselves in the soil.
Watering
Roses are insatiable drinkers, preferring long drinks to short, skimpy ones. Feeder roots develop on rose plants no matter how they are watered, but long support roots develop only if forced to search deep into the soil for water. We try to give our roses 2 inches of water per week, applying water to the soil, not the foliage. Overhead watering can lead to disease problems, so avoid it whenever possible.
Diseases
The most common rose diseases are rust, powdery mildew, and black spot. Powdery mildew is encouraged by warm days and cool nights. It can also occur in overcrowded plantings and in damp, shady gardens where air circulation is poor. The first symptoms are white, powdery mold patches on foliage and stems. Leaves hold their color but can begin to crinkle as the disease progresses.
Rust disease first appears as yellow or orange pustules on the undersides of leaves. As the disease progresses, leaf undersides become covered with masses of rust-colored spores and the upper leaf surfaces show yellow spotting.
Black spots on green foliage are the first sign of black spot disease. Then yellow-fringed rings develop around the black spots. As the disease progresses, whole leaves turn yellow.
We recommend avoiding using chemical sprays, and suggest starting with disease-resistant varieties to keep disease to a minimum. If you do find disease on your plants, remove any foliage that shows these symptoms to keep problems from spreading. If you do chose to use fungicidal spray, it's very important that you read the label and apply according to label directions. Don't assume that if a little bit is good, a heavier dose is better. Use only products labeled for use on roses, and consider trying an organic or milder soap-based fungicides first.
Insects
Many insects attack roses, but the most troublesome in my garden are aphids. Aphids are soft-bodied sucking insects, and they appear in great numbers on tender rose growth. You can control aphids by rubbing them off by hand or by hosing them off with a strong stream of water. Releasing ladybugs into your garden at the first signs of aphids will also help to control these pests. If they persist you can spray your roses with a mixture of 2 tablespoons of liquid Ivory dish soap dissolved in 1 gallon of water to control aphids, or apply insecticidal soap or another commercial insecticide labeled for roses.
Pruning
Most of the serious pruning is done in February/March, just as buds begin to swell on the canes. In summer you can prune as you remove spent flowers by cutting the flowering shoot down to the first leaf with five leaflets. This will help your roses maintain a neater appearance, rebloom sooner, and produce sturdier stems.