April 16th, 2013
People are asking me already about that deadly new downy mildew disease that wiped out just about everyone’s impatiens last year.
I’m not very optimistic that we’re going to escape a repeat this year here in central Pennsylvania.
It’s a highly contagious disease, capable of overwintering, and durable enough to stay active in the soil for 3 to 5 years, the plant pathologists are saying.
Growers are so pessimistic that they’re wondering if they should even bother growing impatiens until we see how it all shakes out.
I’m posting an update on this sordid tale in my weekly Pennlive.com column that’s scheduled to go live April 19. It’ll include a list of my top 10 shade-annual alternatives to impatiens that you might want to try this year. (The column also is to show up in the April 25 edition of The Patriot-News.)
In the meantime, I thought I’d share the assorted questions I’ve been fielding about this new disease.
Q: Where did this come from?
A: The water mold that causes downy mildew has been known since the 1800s, but it didn’t begin devastating garden impatiens in Europe until about 10 years ago.
It’s moved to the United States and has been spreading here since about 2004. It suddenly flared for the first time in central Pa. last summer.
Q: What if my impatiens didn’t get the disease last year. Will I still be able to grow them?
A: You can try, but this disease is extremely contagious. Odds are very good you won’t get away with it again.
Q: My impatiens died last year. Will they be OK if I plant them in a different part of the yard?
A: Unlikely. The disease spreads far and fast by wind and rain. Moving to a different bed nearby will be no big hurdle for it.
Q: How about if I grow them in new soil in a pot?
A: You’ll start out fine, but the odds are good that the disease will get you as well in a pot as in the ground. It just might take a little longer.