QUESTION: Five years ago, I planted Jaune Desprez, a climbing rose with buff and yellow blooms. It had a few flowers the first year and more the next. Then it turned weak and stopped flowering. After I fed it this spring, it came roaring back, but the flowers are a dark velvety red. I don't mind - they look terrific - but how could this happen?

ANSWER: Jaune Desprez, a.k.a. Desprez a Fleur Jaune, is a cross between a tea and a noisette. Rough translation, "Don't try this up north." Though some catalogs say it is hardy to Zone 6, it much prefers life in Zone 8 and warmer. Your delicate beauty made it through a few comparatively mild winters, then died. But the story did not end there because yours was a grafted plant. The rose on top was Mademoiselle Fragile, but the roots and the plant you have now is Dr. Huey, a much sturdier character.

Dr. Huey can be found all over the country. Gardeners who planted something else are often won over by the easy grace of this old-fashioned rambler. And because it can survive without care it is a familiar sight in cemeteries and abandoned yards.

Unlike Jaune Desprez, it is a once-bloomer, but the show is spectacular while it lasts (usually about a month). Starting in midspring or early summer, the long arching canes are covered with clusters of black-red buds, which open to gold-centered flowers.

As long as you are happy with Dr. Huey, everything is rosy. If you want to try another Jaune Desprez, improve your chances by planting one that has been grown on its own roots instead of being grafted. When it dies to the ground, as it probably will, it can still come back as itself.

Sources for own-root Jaune Desprez include Bramble and Rose, brambleandrose.com or 541-547-3848, and Ashdown Roses, 864-468-4800 or www.ashdownroses.com. Dr. Huey is sold by High Country Roses, www.highcountryroses.com or 800-552-2082.

QUESTION: Our organic community garden stores water in large barrels and uses Mosquito Dunks in them to control mosquitoes. Could this make the water unsafe for use on vegetables?

ANSWER: The active ingredient in Mosquito Dunks is Bacillus thuringiensis, or Bt, var. israelensis, which kills mosquito larvae. Like other strains of Bt, it is a good organic pest control, harmless to fish, birds and mammals. Mosquito Dunks are a bit more than 10 percent Bt, and the rest is calcium sulfate (gypsum) and cork. Neither of these is unsafe, but it is still a good idea to rinse produce before you eat it. Pollutants can float in the air as well as in the water.

Address questions to Garden Q& A, The New York Times, 229 W. 43rd St., New York, NY 10036, or by e-mail to gardening@nytimes.com. Those of general interest will be published.