Impatiens Downy Mildew Update
Impatiens Downy Mildew (IDM) devastated bed after bed of the beloved shade annual several summers ago. The disease, which has no cure and few practical preventative measures, changed the bedding plant business by removing the most popular bedding plant sold in America as a garden option for many people.
The story of IDM’s spread was covered widely in 2013 by major new publications including the New York Times and the Washington Post, a very unusual occurrence for a disease of ornamental plants. That coverage, combined with efforts by retailers to help consumers understand the effects of IDM, resulted in a significant decrease in impatiens sales at the retail level.
With fewer customers buying impatiens (Who could blame them? They risked losing entire plantings practically overnight), many growers reduced production drastically over the past few years. Now impatiens can be difficult to find for purchase.
In response, the bedding plant producers rapidly began breeding regular impatiens with other species, particularly New Guinea impatiens, which are immune to the disease. They have been fairly successful in creating resistant plants, but the incredible floriferousness of bedding impatiens took a while to be matched, as did the compact habit.
The best offering so far is probably Impatiens Bounce™, with reports that it flowers almost as prolifically as traditional bedding impatiens. Initial colors are limited, with Pink Flame, Cherry, Lilac, Violet and White Blush, and they grow to 14 to 20 inches tall and wide. The name comes from the fact that they will “bounce” back from wilting with little damage. They are also much more sun tolerant than traditional impatiens thanks to the genetics provided by the New Guinea impatiens. Impatiens Bounce™ Pink Flame is an All-America Selections Flower Award winner for 2015 too, so performance is likely to be very good in the home garden.
Since Impatiens Bounce™ are propagated from cuttings rather than seed as traditional Impatiens were, the per-plant cost will be higher. However, each plant will quickly grow to fill an area of at least 1 ½ to 2 square feet.
Can you still plant traditional impatiens (if you can find them?) Sure, but now that IDM is widespread it will always be a risk. Some areas may see little of the disease from year to year, and others might be as hard hit as they were in 2012.
Anecdotally, the disease seems to have been light locally in 2015. This may be due to the fact that there were many fewer impatiens to develop and spread the disease, or that the ideal environmental conditions were not in place at the right time (the disease favors warm wet weather). Regardless, IDM will likely continue to affect both the health and availability of traditional impatiens well into the future.