Gardeners’ hearts sank when they realized that the much loved shade impatiens (Impatiens walleriana) really was not a good choice for them any more.
The appearance of Downy mildew disease (Plasmopara obducens) in the past two or three years in our Central Iowa bedding plants was inevitable, but devastating nonetheless despite many suggestions for shade loving substitutes. The downy mildew fungus is easily distinguished from powdery mildew, which we all deal with from time to time. While the white growth on the upper side of leaves is easily identified as powdery mildew, downy mildew forms on the underside of leaves and often visual cues aren’t obvious until infection is well underway.
Once infection of downy mildew begins, decline is rapid, including yellowing of leaves, a white velvety coating on the underside of leaves, stunted growth and then complete collapse of the plants. Early on, we thought that buying from growers that had tested their seed was important—study of the disease is showing that even tested seed and seedlings can develop the disease, and once found in a garden bed, is believed to persist for eight to 10 years!
While there are several fungicides that can prevent the disease, no product is known to be able to cure the downy mildew once it has begun. A great University of Minnesota fact sheet recommends bagging and removing a plant root and all if downy mildew is suspected. A good cleanup of the flowerbed at end of season is also important.
The good news is that the disease is very specific to our beloved shade impatiens (I. walleriana). Plant breeders have been busy finding a suitable replacement—the Sunpatiens strain of New Guinea impatiens has been one avenue. But now is an even better alternative in ‘Bounce’ and ‘Big Bounce’ impatiens developed by Ball Seed!
What sets the “Bounces” apart is that they have a more spreading habit, as contrasted with the more upright Sunpatiens and New Guineas. In addition, they have many more blooms so create a feel much more like the I. walleriana. The “Bounce” part of the name refers to another great feature—miss a watering or two? No worries. Water and watch these new varieties perk up and shine once again!
‘Bounce’ is especially well-suited to container plantings, growing 14-20 in. tall and wide. ‘Bounce’ is available in Pink Flame (an All American Select winner), Lilac, Cherry, Violet and White.
‘Big Bounce’ lives up to its name, growing 20-30 in. tall and 20-36 in. wide, making it a great for bedding plant use. This variety comes in Violet, Cherry, Lavender, White and Red. Both varieties can take some sun so offer a bit more flexibility than the older shade impatiens.
It’s also important to note that the ‘Bounce’ and ‘Big Bounce’ impatiens are listed as “resistant” not “bullet proof” to the downy mildew. Mother Nature always has a trick up her sleeve, so it’s not a bad idea to explore other shade bedding alternatives, like coleus, caladium, begonia and torenia.
It will be exciting to see how these new impatiens work in our central Iowa landscapes—the shade will be lit with the happy low-growing color of impatiens once again!