May 2017 UPDATE:Click here to read our 2017 Update about Impatiens walleriana and downy mildew.
If your impatiens were affected by downy mildew, you are not alone. Gardeners throughout the country shared your experience. We’ve created the Q&A below to shed some light on the disease and explain what everyone can do to have a more successful garden next season.
What is it?
Downy mildew is a devastating disease that can spread by air and by the ‘splashing’ of spores due to rain and overhead watering. It is prevalent across the country and can come from any number of places.
What are the symptoms?
Early symptoms include yellowing or stippling of the leaves or a white, downy-like color on the underside of the leaves as well as stunting of growth. Advanced symptoms include a grayish, fuzzy substance on leaves and stems. Leaf and flower drop will eventually result in bare, leafless stems.
How did I get it?
Downy mildew is a water mold. The disease spreads most commonly when the foliage stays wet for extended periods of time and there are cool night temperatures and moist conditions. Therefore areas of deep shade, beds that receive overhead watering and densely planted beds are more highly susceptible to downy mildew. The impatiens you purchased at Hicks Nurseries were healthy, but that does not inhibit them from contracting the disease from the soil or the environment.
What do I do now?
Once the disease is identified remove all of the plants and plant debris (leaves, flowers, etc.) from soil and containers. Spores can overwinter in the plant debris so the removal is imperative to help limit future spread. It is not recommended to plant impatiens in that location for several years. Chemical treatments are not recommended as most are ineffective.
What about New Guinea Impatiens?
Downy mildew only affects impatiens walleriana. New Guinea impatiens have proven to be highly tolerant to the disease.
We at Hicks Nurseries are working hard to react to this disease. We have expanded our annual selections to provide you with a plethora of alternatives to impatiens. If you were lucky enough to avoid downy mildew this year and plan to plant impatiens again next year we may have them available for sale. It is imperative that you plant the impatiens a healthy distance apart, avoiding overcrowding and overhead watering.