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Disease-Resistant Roses Offer Carefree Beauty
Most people don't know that as they stare at the bewildering, gorgeous array of roses offered for sale in winter and spring, that they're also looking at their best chance to nip rose disease in the bud. Do a little research before you buy - find out which roses are most disease-resistant - and you will reduce or eliminate the need for a return trip to buy expensive and sometimes dangerous pesticides.
Admittedly, it's a little tough to offer hard-and-fast rules because, as Kang Mei, a rosarian of the Santa Clara County (Calif.) Rose Society puts it, "a disease-resistant rose in one region might not perform as well in a different region. That's why the best source to find a list of roses that require no spraying is the expert rose growers in your immediate area."
But it is possible to offer both some general guidelines and some specific varieties that are notably more resistant to the rose-lovers' triple threat: black spot, rust and powdery mildew. Most of the single roses (which have a single row of petals around the center) are fairly disease-resistant, says miniature rose enthusiast Sue OBrien, who adds that miniatures also follow this pattern. "Of the miniature roses (which typically grow 6 to 18 inches tall), Herbie and Ultimate Pleasure are particularly disease-resistant," she adds.
Botanists say that the rationale for this rule of thumb is that most single roses are genetically closer in ancestry to the wild roses from which more modern roses have been selectively bred. By selecting for other traits, such as repeat blooming and larger, many-petaled flowers, breeders have often lost a lot of the original disease resistance that wild roses had to have to survive.
New, no-spray rugosas offer carefree color
"Most of the old roses are disease-resistant as a loose, general rule, with some notable exceptions, such as the moss roses," says Marissa Fishman of Greenmantle Nursery in Garberville, Calif. "Rugosa roses are the best; they're nearly immune to everything," she says. (Rugosa roses are a category of roses that includes many varieties.) And although Fishman's interest is primarily in old roses, some mass-market mail-order catalogs are offering some exciting new rugosas as well.
For instance, Jackson & Perkins has just introduced two new rugosas that carry the famous rugosa resistance to disease. "We've got a compact lavender-pink repeat bloomer with a heavy clove scent called Wildberry Breeze," says Keith Zary, vice president of research for Jackson & Perkins. "And we've got another very disease-resistant white rugosa called Wildspice, which has really nice orange hips." The company also offers a new, aptly named white groundcover rose called Magic Blanket that's extremely resistant to disease (at about 2 feet high, it spreads up to 4 feet, and is good for landscaping hillsides and bare spots in the garden).
In the floribunda category, Gruss and Aachen is not only resistant to mildew, but it does well in partial shade, a rarity among roses.
Culture matters
In addition to choosing wisely, you can decrease the need to spray by not overwatering and overfertilizing your plants, says Greenmantle Nursery's Marissa Fishman, who also recommends foliar feedings (spraying the leaves of the plant) with fish emulsion or seaweed-based fertilizer, which she credits with keeping her plants healthy and disease-resistant. And while Fishman cautions that growing roses - particularly for show or commercial purposes - is not easy, proper choice of varieties and good cultural practices can dramatically reduce or in some cases eliminate the need for spraying.
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