published Saturday, September 8th, 2012

Lea: Impatiens fall prey to downy mildew

Pat Lea

Q: My impatiens are a disaster this summer. I gave them my usual care, but they are a leafless, flowerless mess. What did I do wrong?

A: Abandon your gardening guilt. You are the victim of another one of nature's cruel tricks.

Impatiens, our go-to, easy-to-grow, perpetually shade-flowering favorite, has fallen victim to an evil fungus called downy mildew. What you saw -- yellowing, curling and speckling of foliage, followed by leaf drop -- are classic symptoms of downy mildew.

The plants can be infected in the greenhouse where the original plugs were grown. In that case, the problem appears quickly after planting. Or the spores of the fungus can be spread by weather events. For instance, with blowing rain, the spores literally fly on the raindrops.

Climate conditions this summer were optimal for the spread of fungus. The problem has affected many different plants, but none so severely and so incurably as downy mildew on impatiens.

I hate to bring even worse news, but the disease is not only currently incurable, but it is suspected that areas once infected will remain infected for subsequent years. High humidity and consistently wet weather create conditions that favor the spores, not the plants. Since almost every gardener in our region has observed this destruction of their plants, next year may be just as bad as this year.

What can you do? Because you are dealing with a fungus, you need to clean up your bed and probably replace the current mulch with a new fresh layer.

Experts who are dealing with the problem recommend choosing another plant for areas that have shown any evidence of the disease. Begonias, coleus and the more sun-loving New Guinea impatiens can be used for your color display next year. You might consider some shade perennials such as Japanese painted ferns, the silvery ground cover lamium or hostas, which will add some interest and are not subject to this disease.

As with most gardening problems, be patient and hope that the growers and the weather will eventually find a solution.

Email Pat Lea at lea.pat@gmail.com.

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