Patience with Impatiens
When it comes to impatiens, patience is now the name of the game. Beginning in 2012, cases of impatiens downy mildew have been confirmed in our area. Impatiens downy mildew, or Plasmopara obducens, is a fungal disease that thrives in moist conditions, enjoying the heavy dew and high humidity that our summers can bring. It is transmitted by windborne spores or by physical contact - even hands, garden gloves and tools can spread the fungal spores.
Think back to last summer. Did your impatiens look leggy and wilted? Were the leaves yellowish or curled at the edges? Did the flowers drop unexpectedly? Did you notice little spots or a white, fuzzy coating on underside of the leaves? The good news is you weren't the one responsible for killing your plants, but the bad news is these symptoms are the tell-tale signs of impatiens downy mildew. If your impatiens looked fine last year, you can plant impatiens again this year. There is still a risk for infection though, because the spores can spread easily from infected plants in nearby areas. So what now?
Unfortunately, once a plant becomes infected, there is no treatment for impatiens downy mildew. At the first sign of the disease, the best thing to do is immediately pull up the plant. Make sure you remove all the roots; even the cold of winter does not kill off the spores, allowing the ground to become a source of disease for years to come. After pulling them up completely, use a sealed, plastic bag for disposal and do not compost. If in a container, remove and dispose both the plants and soil, clean out the container thoroughly with soapy water, and refill with fresh potting soil. While you don't want to plant impatiens in the same spot, you can plant alternatives there - usually the downy mildew on one type of plant will not affect other types of plants. Moving forward, what can we expect in the upcoming seasons?
Because impatiens are a staple shade annual, growers throughout the region are taking this very seriously. As short-term solutions such as fungicides are not proving successful at controlling this disease, growers are working on long-term solutions through breeding, aiming to eventually develop an impatiens hybrid that will be resistant to impatiens downy mildew. Anticipating reduced demand for impatiens, many nurseries, including Stadler Nurseries, will be carrying fewer impatiens this season. Due to the popularity of impatiens in the past, gardeners have often overlooked other shade-tolerant options. Stadler Nurseries offers many beautiful substitutes, including: New Guinea impatiens (resistant to downy mildew), begonias, torenia, fuschia, caladium and coleus. So, as we patiently await improved impatiens, the next few seasons will be a great opportunity to discover and test out something new for that shady spot in the garden!
Here are some resources and articles for more information on Impatiens Downy Mildew: