In Lewis Carroll's Through the Looking-Glass, Alice finds herself in the Garden of Talking Flowers. These flowers are quite outspoken, criticizing Alice's hair, demeanor and general ignorance about their way of life. If my roses could talk, they would tell me how grateful they were for all the rain this spring, and perhaps they would give me a hard time about how grudging I was with that commodity last year.
They would be correct. The goal was to survive, but not necessarily thrive. If your roses are like mine, they are proving their resilience by putting forth a lovely display of flowers right now. But what can we do to keep them healthy and productive for the rest of the season?
First, remember to water your roses during the growing season. This is especially important for roses that bloom repeatedly. Roses that bloom only once a season (usually known as "heritage" or "old garden" roses) do not need a great deal of water once they are established. All other roses need regular watering.
You can use basin watering or drip irrigation. The latter method allows you to water several plants at once. Overhead watering can help wash away aphids and other pests as well spores and mildew. Do it early in the day so the leaves have time to dry. Dampness can encourage fungi. Inspect the plant before watering to make sure you aren't washing off beneficial insects such as ladybugs. Mulching around your roses will keep roots cooler so the plant will need less water.
Fertilize right after each bloom cycle to encourage more flowering. First remove the spent flowers (a practice known as deadheading), then fertilize. Dry fertilizers dug into the ground are effective. Add some compost while you're at it.
If you practice basin watering, you might prefer a liquid fertilizer. Some gardeners spray the leaves directly with a hose-end applicator. Again, do it early and watch for beneficials.
The New Sunset Western Garden Book recommends dehydrated alfalfa as an organic fertilizer because it smells better than fish emulsion. It's also a good way to add nitrogen to the soil.
Even roses that flower only once will benefit from a meal after bloom. They won't flower again, but the nutrients will promote growth in the spring.
As the first bloom fades, you may notice black spots on some rose leaves. Perhaps some leaves have lost color in places or have a powdery white deposit. Black spot, rust and powdery mildew are common rose maladies in Northern California, especially after a wet spring. Rust (Phragmidium mucronatum) is a fungal disease that leaves the top of the leaf discolored, with rust-colored pustules on the underside. Powdery mildew (Podosphaera) presents as a white powdery coating on buds, stems and leaves.
At the first sign of any of these problems, remove affected leaves, stems, buds and flowers. Pick up any fallen leaves or flowers to prevent the disease from spreading. Put the affected foliage in your yard-waste bin--not your compost bin--for the same reason. Many of my own rose woes can be traced to inadequate cleanup.
Both the University of California's "Rose Pest Notes" and the Sunset book recommend spraying to combat these pathogens. Spray the leaves, not the flowers. For rust, use a garlic-based or copper soap fungicide. For powdery mildew, use Neem oil or other horticultural oils, a baking-soda mixture, a copper soap fungicide or sulfur.
Black spot (Diplocarbon rosae) produces black marks with irregular edges on the top of the leaf. Often the leaf turns yellow. Horticultural oils can help reduce black spot. Oils can coat insects—including bees—so apply them at the end of the day when the insects have retired for the evening.
Roses are exuberantly beautiful, and to me that is reason enough to nurture them through their ailments. Give them a little care and they will reward you with color and fragrance well into autumn.
Workshop: Napa County Master Gardeners will hold a workshop on “Rose Care” on Saturday, June 4, from 10 a.m. to noon, at University of California Cooperative Extension, 1710 Soscol Avenue, Napa. Join the discussion about spring and early summer rose care, issues and solutions. Learn about integrated pest management for common pests and diseases and how to keep your roses healthy during our current drought. On-line registration (credit card only); Mail-in/Walk-in registration (cash or check only).
Master Gardeners are volunteers who help the University of California reach the gardening public with home gardening information. U. C. Master Gardeners of Napa County ( http://ucanr.edu/ucmgnapa/) are available to answer gardening questions in person or by phone, Monday, Wednesday and Friday, 9 a.m. to Noon, at the U. C. Cooperative Extension office, 1710 Soscol Avenue, Suite 4, Napa, 707-253-4143, or from outside City of Napa toll-free at 877-279-3065. Or e-mail your garden questions by following the guidelines on our web site. Click on Napa, then on Have Garden Questions? Find us on Facebook under UC Master Gardeners of Napa County.
