Buyer beware! Impatiens, one of the most common summer bedding plants, is diseased this year.
Plants can die within a week, if affected by an airborne mildew. And, contaminated plants can continue to spread the disease.
Impatiens is for sale at some nurseries and markets, though some garden stores have put up warnings and are offering alternatives to the shade-tolerant bedding plant.
Check the video, with Carol Watson, for impatiens alternatives.
Here's Cornell Cooperative Extension's statement on Impatiens:
Change for Landscape Beds
Brian Eshenaur, New York State Integrated Pest Management Program
It will be different in 2013. We will be seeing less of one of the most popular bedding plants used in landscapesâ??garden impatiens. In fact some New York greenhouse growers who produced thousands of flats in past years will not be growing any this spring. Itâ??s all due to a new disease of impatiens called downy mildew. This devastating water mold (related to late blight of potatoes and tomatoes) became widespread through much of the country over the last two years.
When it shows up it can cause a beautiful flowering mound of impatiens to be a bare stand of stems in a weekâ??s time. One of the challenges with this disease is that itâ??s airborne and even if the impatiens plants that a landscaper installs in a clientâ??s property are completely healthy when they are planted, the disease can move in from windblown spores and in a short time ruin the planting. This happened at some locations in NY late in the summers of 2011 and 2012, most of the landscapers that had plantings affected by this disease are planning to use alternative plants this year. This could be a hard sell for some commercial and residential clients because there are no perfect substitutes that tolerate the shade so well and bloom from spring planting to the first frost. But there are some plants to try and breeders are actively working on new varieties of garden impatiens that will have resistance.
More about Impatiens Downy Mildew
Plasmopara obducens is the name of the water mold responsible for this disease. It can spread quickly with wet weather. Overhead irrigation will increase the risk of infection.
Not only is the disease airborne it can also survive overwinter in the soil through spores in infected plant debris. When impatiens are planted into infested soil the disease is likely to appear sooner in the growing season.
It is not practical to treat infected landscape plantings with fungicides.
All varieties of garden impatiens (Impatiens walleriana) are susceptible but other New Guinea impatiens (Impatiens hawkerii ) and other bedding plants are not susceptible.
Some plants that landscapers may consider as a substitute for garden impatiens:
Begonia (both wax and the new angel wing varieties)
New Guinea impatiens
New guinea impatiens are one of the alternative that are resistant to downy mildew.