Green Scene

The temperamental rose offers rewards in color, fragrance and luxuriance

By Joel M. Lerner
Special to The Washington Post
Saturday, June 5, 2010

In 1986, the rose, official flower of the District of Columbia, became the national flower of the United States as well. It's also the official blossom of Georgia, Iowa, New York and North Dakota -- making it most popular choice for a state flower. But this popularity is somewhat curious, as gardeners know roses are fraught with disease and insect problems.

With proper cultural conditions, roses offer beautiful flowers. We have had those conditions so far this spring: low humidity, cool temperatures and ample rainfall followed by drying winds to discourage fungus. And roses had great snow cover for winter protection this year. You can build on this optimal setup by following these cultivation practices so that roses remain healthy -- and flowering.

-- Give them the best soil. Roses thrive in a light-textured, friable planting medium. Dig the planting hole to a minimum of two feet deep and wide. Then mix two-thirds native soil to one-third compost or manure in the hole. Remove the rose bush from the pot and set it into the soil mix, being careful not to disturb the small, wiry absorption roots. Place the rose so the roots are in the ground and the base of the trunk is at ground level. Be sure that grafted roses are planted with the graft scar above ground. Protect the plants with mulch in winter.

-- Protect them from deer, which like to eat roses. Commercial repellents use animal products, such as putrescent egg solids, to make the plants unappealing to deer. Most repellents remain effective for about 30 days. Two products that I have tried with success are Liquid Fence and Deer Stopper. Deer don't like strongly scented plants, so mint and rosemary are deterrents, as are plants with fuzzy (tomentose) leaves. Installing a deer fence is another option. It should be eight feet high. In some jurisdictions, a six- to seven-foot fence is the maximum. In that case, plant evergreen shrubs or conifers on each side of the fence, creating the illusion of a wide area, so that deer are afraid to jump over it.

-- Water carefully. Roses prefer moist, deep, well-drained soil. The soil moisture is sufficient now, but if the D.C. region has a drought, roses would need deep watering at their base once or twice a week. Keep water from splashing onto the leaves of the plant to control leaf fungi.

-- Prune roses before growth begins in spring. Cut out old canes with thick stems and all deadwood. Clean pruners with bleach after using them to cut dead or diseased wood, before you use them on healthy canes. Lubricate pruners with light oil to discourage corrosion.

-- Add a fresh layer of ornamental mulch only after you have removed the old mulch. One to two inches of decorative mulch is all you need. Too much can impede air and water penetration.

-- Maintain weed-free beds. Pull existing weeds. Apply a pre-emergent weed killer in late fall and late winter. One safe material is a corn gluten meal powder that keeps seeds from germinating. It's sold under many names. A few I am familiar with are: Granulated Wow! Pre-Emergence Weed Control; Organic Traditions Corn Gluten Weed Preventer; and Planet Natural Corn Gluten Meal. Use the material in freshly weeded beds for best results. and water it in if used over mulch. As always, follow label instructions.

-- Spread an organic rose fertilizer around the base of the plants once a year, in spring. Espoma Rose-tone is one commercial product with a good balance of nutrients. Many rosarians have their own organic recipes; fish, banana peels, dried alfalfa and liquid kelp are a few.

-- Boost plants' immune systems with Employ Plant Health Promoter. Plant Health Care changed the name of this product from Messenger to Employ and added an immune booster. The company claims to have improved the original product and named it Harp-N-Tek. Employ is not a fertilizer, growth stimulant or enhancer, pathogen or pesticide. It's a Harpin protein -- a natural protein that activates a plant's self-defense system to respond to the presence of disease. Harpin proteins build strong plants that are able to resist broad spectrums of viral, fungal and bacterial diseases. Once the plant's defense system has been triggered, Harpin proteins quickly disintegrate, having never entered the plant and leaving no detectable Harpin residue. Employ is a natural product, but is not certified USDA Organic.

These guidelines are applicable to all roses, but some of the free-flowering, disease-resistant groundcover roses and tough native varieties do not need regular fertilizer or Harp-N-Tek.

Breeds apart

Thousands of rose varieties have been bred over thousands of years. Even the latest hybrids were introduced from about 12 original species. Rose breeders can produce almost any characteristic they desire. The line between categories blurs with each new introduction. The greatest difference among them is flower, color, length of bloom and plant size.

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