Photo by Steve Bender

For more than three decades, impatiens have reigned as the most popular bedding plants in America for three very good reasons.

  1. They bloom nonstop from spring to frost.
  2. They smother themselves with showy flowers of just about every color but blue.
  3. They bloom well in shade.

But now a weird malady racing like Mongol hordes across the land threatens their existence. Downy mildew. Nobody is sure where this disease came from, but it has already killed thousands and thousands of impatiens quicker than Grumpy can scarf down a cold brew. Lloyd Traven, the highly respected owner of Peace Tree Farm in Kintnersville, Pennsylvania, tells Grumpy the problem is so serious in Europe that no traditional impatiens were planted there this year. "The same will happen here," he predicts.

Don't Jump Off the Roof Yet Before the dire news convinces you to head to the top floor and put an end to your suffering, let Grumpy suggest two things. First, don't jump without leaving a will or there will be two big messes for your family to clean up. Second, realize that downy mildew doesn't kill all kinds of impatiens, just traditional impatiens (Impatiens walleriana) and most of its hybrids. New Guinea impatiens (Impatiens hawkeri) and three popular series developed from it, Fanfare , Sun Harmony, and SunPatiens (shown above), are immune. These latter two like sun as well as shade and also combine large, beautiful flowers in many different colors with handsome foliage.

How Downy Mildew Spreads Downy mildew is a strange beast. It isn't a fungus like powdery mildew. It's a water mold and requires water for its spores to spread, germinate, and infect plants. So impatiens that stay wet for a long time are perfect targets. And how do impatiens stay wet?

  • Being planted in dense beds with poor air circulation that keeps water on leaves from evaporating.
  • Being planted in full shade that slows drying of the foliage.
  • Being watered at night when it's cool.
  • Being watered using overhead sprinklers that wet the leaves. Splashing water spreads the spores from plant to plant.

Signs of Downy Mildew What does downy mildew look like? Ranked from bad to horrible, here are 3 signs of downy mildew on impatiens.

Photo by Laura Sanagorski.
  1. Speckled, off-color leaves.
  2. Leaf edges that curl downward.
  3. A white, downy layer on the undersides of the leaves.

Can Downy Mildew Be Prevented or Cured? Cured, no. Once you see the whitish matting on the leaf undersides, it's bye-bye impatiens. No fungicides available to homeowners will work. Your plants will defoliate, collapse, and die. The only thing to do at this point is rip out the plants, seal them in a trash bag, and put them out with the trash.

Prevention, however, is possible. Because downy mildew spores can survive in the ground over winter, don't plant impatiens where other impatiens have died. Don't shove impatiens plants close together. Don't water using overhead sprinklers. Next year, plant New Guinea impatiens, Fanfare, Sun Harmony, and SunPatiens instead of regular impatiens.

Oh, By The Way….. A single impatiens plant is not "an impatien." Two impatiens plants are not "impatienses." The word "impatiens" is both single and plural. So speak correctly. Don't test my impatience.

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