Downy mildew threatens to destroy impatiens crop

Written by Doug Oster on .

blog impatiens downy2aThese impatiens show signs of downy mildew and were dead within a week. Photo by Doug OsterThere are more questions than answers about downy mildew, the disease which killed countless impatiens last season.

I lost my entire crop and since I garden in the shade, I'm looking for alternatives in case the disease is widespread this year.

It's hard to say what's going to happen this season. Many growers and garden centers are concerned about even offering impatiens this year for fear of the disease.

Plasmopara obducens is the scientific name for the disease and it infects the species Impatiens wallerina. One the bright side, New Guinea impatiens are not affected. Those varieties are bred to grow in more sun, but I've found they will flower in part shade. I've grown Sunpatiens for a few seasons and love them. Even though they are sun lovers, the plants will also bloom in some shade and are resistant to the disease.

Downy mildew was discovered in more than 30 states last year and once the plant is infected, it's doomed. Yellow spots form on the leaves and a white mold on the undersides. In a short time the plant wilts and dies.

Many growers are using fungicides as a preventive measure and gardeners should follow certain cultural practices to try and avoid the disease. Watering at the base of the plant and using mulch should help. The spores spread in the soil, water and can be carried by the wind too.

Serenade is an organic fungicide which will help prevent downy mildew. The fungicide must be applied BEFORE signs of damage have occurred. Even then, it's hard to tell if the disease can be held in check.

If the season is wet and humid, I'm afraid growing impatiens might be a losing battle.

Regardless, I'll be attempting to grow impatiens this year, but I'm drafting a contingency plan in case I loose them. Here's a list of other plants to grow instead of impatiens-

Begonias- There are many varieties, colors and forms to this plant. They are easy to grow and are beautiful. I like a variety called 'Gryphon' which is grown for its foliage.

Caladiums- They don't flower, but the pretty leaves a show stoppers.

Coleus- Another foliage plant which thrives in the shade.

Torenia- Wonderful annual which blooms all summer.

New Guinea impatiens- They do better in sun, but will bloom in the shade.

Euphorbia- Pretty drifts of white flowers bloom all summer and will continue a while after a frost.

Pansies and violas- They are best in cool weather, but if kept fertilized and watered in the shade they can bloom all season.

Corydalis lutea- Even though this plant is a perennial, it blooms from April to October or later. It loves dry shade and will form a nice colony in only a few years.

It won't be the same if impatiens become extinct, but like a garden, everything changes from season to season.

Here's a great resource about downy mildew and its effect on impatiens.


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