by BRIAN MINTER
June 1, 2000
It never fails. Just when your Roses are full of buds and ready to burst into bloom for a great summer display, disaster strikes. Mildew, rust, blackspot, aphids, mites, beetles and funny curled leaves all seem to appear overnight making a mess out of a beautiful rose. If that is the case with your Roses, don't be discouraged. These pests and diseases are common to all rose growers. How you prevent them from becoming a serious problem determines the success or failure of your Roses. The first step to prevent most problems is the selection of the Roses themselves.
Generally when people select a rose, their first considerations are colour, form and fragrance. What about disease tolerance? Unfortunately, many great old-fashioned Roses have become so susceptible to diseases that they are hardly worth growing. 'Tropicana' is a prime example. On the West Coast, it gets mildew and black spot far too easily. A little effort is needed to find information on the best local Roses. Rose societies often publish lists of the best varieties for their regions, and whenever you have an opportunity to visit any of the fine public and private gardens of B.C., take advantage of the occasion to check out the Roses. Note the time of your visit and the weather conditions, then examine the foliage. Glossy foliage is usually a sign of a rose with fairly good fungus tolerance.
When considering rose varieties, don't discount hardy rugosa Roses. Their blossom form and foliage is not spectacular, but their fragrance, fall hips and disease-free nature make them a real treat. Many antique Roses are very disease tolerant too, and although most tend to bloom only once, their foliage and fragrance are outstanding. The new 'Flower Carpet' ground cover is very good also, once it’s established.
After selecting your Roses, you must next consider the planting site. Is it well drained and sunny, and does it have good air circulation? If trees are blocking the air flow, you are asking for trouble.
I am a firm believer in the philosophy that healthy plants are usually the last to be affected by diseases and insects. Make sure you plant your Roses in rich organic soil. Water and feed them as necessary, never letting them become too hungry or too dry.
The real key to successful rose care is a preventive maintenance program. You practice it with your car, so why not with your Roses? If you are an organic buff, Louise Riotta, in her book 'Carrots Love Tomatoes', claims that, "All the alliums - garlic, onions, chives and shallots - are beneficial to Roses, protecting them against blackspot, mildew and aphids." She also states that, "Roses are also aided by the presence of parsley against rose beetles, onions to repel rose chafers, mignonette as a ground cover, and lupines to increase soil nitrogen and attract earthworms." You can also use many organic pesticides from ‘Rotenone’ to ‘Dipel’ to control insects. You might even try Safer's ‘Trounce’ as a broad spectrum preventive spray. The secret is to use them regularly and to alternate them for more effective insect control.
As for the many rose diseases, I have found that a regular spraying program, before any disease problems appear, is by far the best way to go. I recommend the systematic fungicide ‘Benomyl’, alternated with either ‘Funginex’ or soluble sulphur powder, as one of the finest ways to guarantee you never see blackspot, mildew or rust.
The last thing I would like to recommend is the regular feeding of Roses with a proper fertilizer. Roses burn off a lot of energy blooming all summer, and they need regular applications of compost and manure. They need lots of phosphate and potash, as well as micronutrients. I have had great success with Green Valley 6-12-14 applied every two months. In aliition, during periods of heavy bloom, I supplement with Miracle Gro liquid rose food to keep that new growth coming.
Regular feeding and a preventive spraying program will make quite a difference in your Roses now and all summer long, and it's not a lot of work. Act now to get those Roses in shape for summer!