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GardenSMART :: Impatiens and Downy Mildew

Impatiens and Downy Mildew

By Therese Ciesinski, GardenSMART

Am I the only one who really misses the annual bedding impatiens? There was a time, not long ago, when impatiens – known by their common name busy Lizzies – was the gardeners' go-to annual for brightening shady areas of the garden. Inexpensive and plentiful, the cheerful white, pink, orange, red or purple flowers provided non-stop color from early summer to first frost.

In fact it was once the most popular annual bedding plant in the U.S. But this kind of impatiens (Impatiens walleriana) has become scarce these past few years. That's because a fungus called downy mildew has decimated impatiens throughout North America and in Europe.

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Mary Ann Hansen, Virginia Polytechnic Institute and State University, Bugwood.org

Impatiens downy mildew (Plasmopara obducens) was first discovered in production greenhouses in the U.S. in 2004, and was widespread by 2012. The fungus – a white fuzz that grows on the underside of leaves – causes plants' lower leaves to yellow and droop. Then the plant defoliates entirely. There's no way to treat it; fungicides don't work. Once the fungus appears, it is inevitably fatal. It has infected millions of growers' bedding impatiens, causing financial losses and creating a void in the home landscape in those places where the sun doesn't shine.

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Mary Ann Hansen, Virginia Polytechnic Institute and State University, Bugwood.org

The mildew lives in the soil and thrives where it's cool and wet. Home gardeners who had infected Impatiens walleriana plants were advised to pull them out, put them in the trash, and avoid planting impatiens in the same soil in the future.

There are some impatiens varieties that are not affected by this type of downy mildew, including New Guinea impatiens (Impatiens hawerki), Sunpatiens, and the Bounce series of hybrid impatiens. While lovely, they cost a good bit more than the cheap six-packs of I. walleriana you could pick up at the supermarket, which means filling a large space gets pricey quick.

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Photograph courtesy of PanAmerican Seed.

This year there's a new, highly resistant introduction of I. walleriana. Called the Beacon Series, plants grow a foot tall and come in seven colors: orange, orange star, red, rose, violet, salmon, and white. Beacon impatiens are available by both seed and plants. Right now they can be ordered online from Ball Seed or Burpee; more growers and garden centers will offer them as time goes on. Information about the Beacon Series can be found at beaconimpatiens.com.

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Photograph courtesy of PanAmerican Seed.

The silver lining for me at least is that losing my go-to shade favorite forced me to investigate alternatives I wouldn't have bothered with otherwise: coleus, begonias, torenia, caladiums, hypoestes, oxalis, and of course New Guinea impatiens, to name a few. Experimenting with new plants, whether I end up loving them or not, is never a waste of time. But with that said, I will be happy when I have my hard-working, cheerful and easy care impatiens back.

 


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