JT's Blog

Things that interest me, things that happened to me, things that I like, even some things that I don't like...

Impatiens

Impatiens planted last year on the northeast 50.

Last year I had great success planting impatiens plants. In fact, I was just getting ready to order a whole bunch more for this year to fill the flower beds along my wall.

Then I found out that planting impatiens this year might not be such a good idea.

The culprit in this gloomy scenario is well-known in the trade and virtually unknown to consumers: downy mildew, a deadly, fungus-like disease that targets the popular garden plant known as Impatiens walleriana.

In 2011, the disease was confirmed in 11 states. In 2012, it was in 34, including Pennsylvania and New Jersey. The damage this year is anybody's guess, but there's no question there will be damage.

"The feeling is, it's really going to be pretty much everywhere," says James Harbage, research and production leader at Longwood Gardens in Kennett Square.

That doesn't sound good.

But wait. It gets worse.

Once the plant is infected by the mildew spores - found in soil, water, and winds from as far away as a hundred miles - small yellow spots appear on the tops of the leaves and fluffy white-gray growths on the undersides.

There's no cure, and no affordable, foolproof way to forestall the end. The plant shrivels and dies in a matter of days or weeks, while the offending spores can live on in the soil for a year or two or more.

Cool temperatures, high humidity, and moisture from rain and overhead sprinklers or irrigation systems fuel the spread of the disease. And spores in the ground can survive the winter.

"They've figured it out. During dormancy, they form a very thick-walled spore that's resistant to cold and flooding and drought," says Gary W. Moorman, Pennsylvania State University plant pathologist. He believes that the downy mildew problem could cripple impatiens production and sales for years.

So what else will grow in partial shade?