Recently a number of Long Islanders have come to Hicks with questions about their impatiens. They mention that the leaves of the plants are yellowing and the undersides have developed a white, downy-like color. These are classic symptoms of downy mildew, a water mold that affects impatiens walleriana and has no known cure.
As a leader in the garden center industry on Long Island, we stopped selling impatiens walleriana several years ago. We continue to feel it is our responsibility to help stop the spread of downy mildew by instead offering alternative annual plants that will thrive in your Long Island garden.
If you purchased impatiens walleriana at another nursery and think your impatiens have been affected by downy mildew, here is what you need to know:
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.
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.
What else can I plant?
There are many other beautiful flowering plants that thrive in shade. Take a look at our handout “Great Annuals to Replace Impatiens” for additional information.
At Hicks Nurseries we continue to follow the research of Cornell Cooperative Extension and various test gardens. If you have any questions about downy mildew please stop by the nursery*, call us at 516-334-0066, email us at HicksInfo@HicksNurseries or reach out to us on Facebook or Twitter. Our number one goal is to help you be successful so that you may enjoy your garden for many years to come.
*If you would like to bring a sample of your impatiens to the store for closer inspection, please place your sample in a sealed plastic bag and bring it to the Garden Care Information Desk.