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Impatiens Update

For years you looked out onto your shade garden and marveled at the color and beauty of the impatiens you had planted. Now you hear you can no longer plant impatiens and you have to change to a different plant. New Guinea impatiens, sun impatiens, wax begonias or shade coleus are great substitutes and offer a great deal of color.

Maybe it will help put your mind at ease if you understand a few characteristics of the disease that is affecting impatiens. First of all, please understand that it is not the plant itself that is diseased. At Gertens we take every precaution to make sure that the plants you buy are in the best condition possible. They are sterilized when they are planted and they are disease free. There is no evidence the pathogen is transmitted to the plant by infected seed.

Impatiens Downy Mildew
Impatiens Downy Mildew


What is Impatiens Downy Mildew?


What we are talking about is known as impatiens downy mildew which is caused by the fungus Plasmopara obducens. It is specific to Impatiens walleriana. It does not affect New Guinea Impatiens, Sun Harmony Impatiens, Double Impatiens or Sun Impatiens. In addition, the pathogen does not affect other garden plants.

Impatiens downy mildew is spread through the air. It began in the eastern United States and is working its way to Minnesota. It is hard to estimate how many gardens have been affected, but chances are if your neighbor has it, you will soon.

Early syptoms are some slightly yellowed leaves. Later, leaves and flowers start to drop and the leaf undersides turn white due to a coating of white spores. The organism that causes the disease is classified as "water mold" a fungus that thrives in wet conditions. Ideal conditions are cool days with water from rain, sprinklers, dew or fog, and cooler nights. In dense plBonide Fruit Tree and Plant Guard helps control impatiens downy mildewanting, it is easy for the disease to spread by spores that splash from plant to plant.

Because of the possibility of survival spores in the soil, it is a good idea not to plant impatiens walleriana in the same area they were planted last year. Plant pathologists have no idea how long the survival spores could live in the soil. Based on studies of other downy mildews, the spores could live for five to eight years - or longer.

What's a gardener to do? First of all, if you have had downy mildew in your garden in the past, try another bedding plant. Try planting impatiens in a container. Be sure to use fresh soil each year to ensure success.


Controlling Impatien Downy Mildew

If you are one of the lucky ones who have not had downy mildew, Gertens recommends Bonide "Fruit Tree and Plant Guard." Early indicators suggests that following the directions on the label will help to alleviate downy mildew on your impatiens.


Other suggestions include avoiding large plantings of impatiens and avoiding wetting the leaves of existing plants. It is wise to remove infected plants, because the spores on the leaves can be carried not only by splashing water but wind can infect nearby plants. When you take out your plants in the fall, be sure to get the roots and any fallen leaves and flowers as well. Do not compost the plants you remove.

At Gertens we always strive to give you the very best and we hope this information will be informative in planting your shade garden.