Are you scratching your head wondering what happened to your impatiens plants last year? They all developed something called Downey Mildew (plasmopara obducens). Affected plants seemed healthy one week and were gone the next.
Downey Mildew is a very aggressive disease. In the early phase, yellowing and curling of the leaves is present. Turn them over and you will see white powdery spores on the undersides. The late stage is complete defoliation. This happens within a matter of weeks.
This disease was first found in the UK in 2003, then California in 2004 and in Delaware in 2012. Downy Mildew quickly infects plants when dry periods are followed by wet conditions. It is rampant along the east and west coasts of the US. It can be spread by water splash over a short distance and wind over longer distances.
The problem still has not been resolved, so do not plant impatiens walleriana until then. The spores can overwinter where infected plants have been.
Growers are frantically trying to find a solution to this problem. Until then, you have other choices for your shady garden areas.
New Guinea impatiens are not affected. Coleus, caladiums, all types of begonias, torenia and browallias as well. These shade lovers can be purchased in most garden centers.
You might be disappointed at not being able to grow your beloved impatiens, but you could be surprised at how creative you can be in combining the other shade-loving annuals listed above.
I will post a notice on my web site when it is safe to plant impatiens walleriana again. In the meantime, Happy Spring!