by Nancy Lindley
You can prolong the fabulous show that roses put on in June just by following a few simple steps to keep roses healthy for the summer. Here’s how.
Look at your garden. Are your roses receiving at least six hours of direct sunlight? If not, consider thinning out overhead tree branches. Are they planted too close to other plants? If so, relocate those plants and give your roses some space.
Maybe your roses are planted too close to a wall. Did you know it’s easy to move them by root pruning in summer to get them ready for transfer in fall when they’re dormant? To root prune, cut a circle around the shrub with your spade, much like you were digging them up. However, don’t do that final thrust that rips the roots out. Fertilize as usual, and keep the plant well watered. Do this several times throughout summer. This will create dense, compact roots that respond well to moving. In the fall, dig out your rose with a root ball slightly larger than your pruning circle cut, then transfer your plant to its new home.
Roses need much more water than they receive from typical rainfalls, and more water than home irrigation systems provide for turf grass. How much is enough? It depends on your soil, mulch and air temperature. To determine if your roses need watering, dig a small hole a few inches deep near the plant’s base. Check the soil’s moisture content. If in doubt, water.
Unless your spring fertilizer was a slow-release type, fertilize your roses every month or so during the growing season. To promote repeat blooming, deadhead (remove) spent blooms to prevent the formation of rose hips (seed pods).
Hybrid tea roses have long stems and are good for cutting. Make your cut about one half inch above a leaf cluster with five or more leaflets. A new shoot will emerge above that cluster and just below your cut. To prolong the life of cut roses, take a bucket of warm water into the garden. Immediately after cutting the rose, hold the stem underwater and make a new cut about an inch above the end of the stem. Doing this brings water, not air, into the stem. To condition the roses, place the bucket in a dark, cool room for several hours. Now they’re ready to be arranged in a vase.
Common Michigan pests
While working with your roses, watch for pests or unusual growths and immediately correct any problems. Here are some common insects and diseases that can attack Michigan roses.
Aphids. Small insects that congregate near the tops of roses and suck the life from tender, new growth. Their “honeydew” (waste) is ideal for mold and mildew growth. Remove aphids by hand, or blast them off with a high-pressure water spray daily. On the ground, predators will feed on them. If you must use a pesticide, select a low environmental-impact product, like neem oil or insecticidal soap.
Spider mites. Unlike aphids, spider mites lurk on the lower leaves of a rose. They are difficult to see, but not the problems they cause: lower leaves take on a bronzed, crispy appearance. Spider mites prefer miniature roses and thrive in hot, dry areas. The best treatment is a daily, high-pressure water blast. These mites resist insecticides, but they can be smothered with neem oil.
Japanese beetles. These large, shiny green beetles are common in Michigan and prefer feeding on roses with yellow and white fragrant blossoms. Remove these pests from plants by hand and drop them into a jar of soapy water. Stepping on them may help females release their eggs. Also consider treating your turf to kill the grubs that will become this year’s Japanese beetles. Beetle traps are not recommended because they lure the pests into your vicinity where they might feed on your roses before reaching the trap. Most effective insecticides are fairly toxic and need to be reapplied every few days. More friendly neem oil products are recommended.
Two common types of fungal infections
Powdery mildew. This gives new foliage a powdery, sugar-frosted appearance, usually in spring or fall. Red roses are prone to this fungus. The best treatment is a daily high-pressure water blast. If you grow varieties susceptible to mildew, consider applying a fungicide every 10 to 14 days. Read application instructions carefully. If your plants are located in an area of poor air circulation, consider moving them.
Black spot. This dreaded summer fungus appears as black spots on lower leaves and occurs because leaves are left wet continuously for seven or more hours. Soon the leaves turn yellow and fall off, then new leaves higher on the plant become infected. Nothing will cure the spots once they develop. However, you may help save your plant by removing all infected leaves and begin spraying regularly with a preventive fungicide.
Perhaps your best “cure” is to prevent this problem (and powdery mildew) from ever occurring in the first place. To do this, bathe your plants with an early morning shower. That way, leaves can dry quickly as the day wears on. Also consider planting rugosa roses, which are highly resistant to black spot. Talk to garden center professionals about other resistant varieties.
Summer pruning of climbers, rugosas, and once-a-year bloomers
Some roses, such as hybrid teas and miniatures should be heavily pruned in late April or early May, before their first bloom cycle. However, the best time to prune climbers, rugosas, and once-a-year blooming antique roses is June. Each year, remove about 25 to 30 percent of their total wood to keep them looking fresh. Do this by sawing out their oldest, woodiest canes at the plant base with a pruning saw. This thinning process encourages new growth from the base and reduces plant size. You can further reduce the plant size by cutting it at the top of the plant, but do this after the major thinning cuts.
Climbers benefit from this late-spring annual thinning. Also in late spring, prune back a climber’s side shoots that emerge along the length of lateral (horizontal) main canes. New blooms will develop at the end of these shoots. Once your climber completes its first bloom cycle, prune these side shoots down so that only a couple sets of leaves are left on each side shoot. This will encourage new side shoots (and blooms) to form.
Follow these few simple steps, and you will be rewarded with beautiful bouquets from June to October.
Nancy Lindley was the co-owner of Great Lakes Roses.