Get your roses ready for this year’s bloom with spring pruning.
“Most roses sold today are bred to be winter-hardy and relatively disease resistant, so they need much less care than old-fashioned hybrid tea varieties,” said Sharon Yiesla, plant knowledge specialist in the Plant Clinic at The Morton Arboretum in Lisle. “But even these hardy shrub roses will flower more and be more enjoyable with a little attention in spring.”
Here are some tips from the Plant Clinic for a spring rose tune-up. To shield your hands against thorns when pruning, wear leather or leatherlike gloves. Gauntlets — gloves that reach the elbow — offer more protection against scratches.
Know your rose. Different cultivated varieties, or cultivars, of roses need different pruning, depending on when they bloom. Many kinds bloom on new wood — stems that have grown this year. Pruning back older stems will encourage the growth of new stems that can develop flower buds. Some older varieties bloom on old wood that is in its second year. Research your rose to determine what pruning it needs or, if you don’t know the cultivar name, leave it alone for a year and note whether it blooms only once in June or reblooms through the season.
Clear out and shape up. On any rosebush, prune out all dead branches as well as any that are damaged, rubbing on another branch or headed in the wrong direction. Cut them back close to the ground. If a stem is only dead partway down, cut it back into the green live wood. “Only live wood can produce new stems or flowers on a rosebush,” Yiesla said. Prune other stems as needed to shape the bush and give it a balanced form.
Make air space. Many of the diseases that afflict shrubs, including roses, are caused by fungi that thrive in moist environments. Good air circulation will allow leaves and stems to dry out, discouraging disease. To open up a bush that is dense and tangled with old growth, remove a third of the oldest stems near the ground. Older stems will be thicker and have dark brown bark; newer stems will have a green tinge.
Check for suckers below a graft. Some rosebushes are grafted, meaning that a plant of one variety has been joined to the roots of another type. The graft union, a bump on the main stem, should be just beneath the surface of the soil, but sometimes stems will grow up from below it. These stems, called suckers, are a different variety than the top growth and will have different flowers, as well as drawing energy and resources away from the main plant. “Cut them off close to the ground,” Yiesla said. Grafting used to be more common, but many of today’s rose bushes are grown on their own roots.
Clean up to deter disease. Reduce the disease risk by cleaning up all fallen rose leaves left from last year, which can harbor fungus spores or bacteria. Rather than putting these leaves in the compost pile, put them out for landscape waste pickup, along with all the stems you’ve pruned from rose bushes.
Spread mulch. Like all shrubs, trees and perennials, rosebushes benefit from a layer of mulch over their roots. Use a coarse material such as chipped or shredded wood. Spread it 2 to 3 inches deep and keep it an inch away from the bark of the stems. The mulch will keep water from evaporating from the soil and moderate the soil temperature. As it decays, it will enrich the soil for the rosebush’s roots.
Deadhead. “Clip off rose blooms once they start to fade, and you’ll encourage the rosebush to grow more twigs with more buds,” Yiesla says. This practice, called “deadheading,” prompts the plant to keep putting its resources into making new flowers, rather than turning its spent blooms into fruit and seeds. Deadheading mainly works on reblooming roses, but even if your bush is one of the old rose varieties that only flowers in June, deadheading can prolong its bloom for a week or so. Stop deadheading in August to let the plant prepare for winter.
Water diligently but carefully. Roses need a good water supply to keep blooming. Water thoroughly when the top inch of soil is dry. “Don’t let the roots sit in wet soil,” she said. “Roses prefer excellent drainage.” Getting the stems and leaves wet encourages fungal diseases. Rather than using a sprinkler to water from overhead, aim a hose spray at the soil near the base of the shrub, so the water soaks down to the roots.
Use slow-release fertilizer. A steady, slow supply of nutrients will encourage reblooming roses to set more flowers. Scatter pellets of slow-release fertilizer around the base of the plant, following the package directions. Stop fertilizing in late July to give plants time to get ready for winter. All organic fertilizers are slow-release.
For tree and plant advice, contact the Plant Clinic at The Morton Arboretum (630-719-2424, mortonarb.org/plant-clinic, or plantclinic@mortonarb.org). Beth Botts is a staff writer at the Arboretum.