Impatiens are very popular for their gorgeous, petite blooms and their ability to grow in shady areas. But widespread outbreaks of downy mildew disease have been wiping out impatiens and leaving homeowners with big, ugly bare spots in their gardens. Don’t let all the time, money and effort you put into your garden go to waste! Here is the lowdown on downy mildew, how to prevent or avoid it, and what to do should your impatiens come under attack.
What is Downy Mildew?
Downy mildew is a fungal disease caused by an organism called Plasmopara obducens that attacks all varieties of Impatiens walleriana. The spores penetrate the plants’ leaves and cause damage that eventually leads to the death of the plants. Plasmopara obducens spores can travel through the air. This makes the disease extremely contagious to other plants. Once the spores reach a leaf, they can use drops of water on the leaf’s surface to spread quickly to other parts of the leaf.
The first sign of a downy mildew infection is yellow or light green stippling on the bottoms of the leaves, which later turns to a powdery white. If the infection is allowed to progress, the leaves and flowers will eventually drop off the plant, and the plant will die.
To keep your impatiens from developing a downy mildew infection, make sure you buy plants only from reputable growers. Examine the bottoms of the leaves for any signs of downy mildew before you buy, and tell the grower if you see any signs of infection. If you grow your own plants, make sure your greenhouse has good air flow and low humidity, and keep the leaves dry.
Applying fungicide to your impatiens can also help prevent infection.
Check the bottoms of the leaves frequently to catch downy mildew early. If you see signs of downy mildew infection in any of your impatiens, place a bag over the plant and remove it immediately, including the roots. Don’t leave any part of an infected plant in your garden, because the downy mildew can get into the soil and live for years. As a result, it can infect new plants in future seasons. After you remove the infected plants, spray all of the healthy plants with fungicide to prevent infection. Fungicide only works well as a preventative, though, not a cure, so all infected plants have to go.
Downy mildew is a disease that is specific to Impatiens walleriana. If you live in an area that has had an outbreak of downy mildew, you might want to consider using other flowers in your garden to avoid this problem completely. Here are a few options.
- New Guinea Impatiens
New Guinea Impatiens look very similar to Impatiens walleriana (see photo), but aren’t susceptible to downy mildew. These colorful flowers come in purple, red, orange, pink or white varieties. They even like the same conditions that Impatiens walleriana thrive in. This is an easy choice for the impatiens enthusiast who doesn’t want to worry about downy mildew.
Fuchsia is a wonderful choice for adding some zest to your shade garden. It has exotic-looking dangling blooms reminiscent of bleeding hearts. The classic fuchsia plant has blooms with very striking bright pink and deep purple coloring. Other color combinations are also available, such as pink and white or solid red.
Begonias are beautiful plants that do very well in shady areas. They are not picky about soil types, and adapt well to many gardens. Begonia plants are about the same size as a medium-sized impatiens plant. Their flowers are similar in size, as well. Begonias have gorgeous, slightly frilly blooms that come in a variety of colors, such as these striking orange and yellow “Pin-Up Flame” begonias. These hardy beauties make an excellent addition to any shade garden.
Whether you stick with Impatiens walleriana or take your shade garden in a new direction this year, staying informed is key for having a beautiful, healthy flower garden. Happy gardening!
(Photo by Rob Hille)