GARDENING GODDESS • BY KATHY JENTZ
Downy Mildew Disease Drives Local Gardeners to Search for Inventive Solutions for Color in the Shade
You may have heard that a soil-borne disease, Impatiens Downy Mildew, hit the Eastern half of the U.S. last summer. Some had it worse than others. If you grew Impatiens walleriana and you were not impacted, count yourself lucky. For those hit by it, whole beds and containers of Impatiens seemed to collapse and lose all their flowers and foliage overnight.
It spreads when sporangia (sac-like structures filled with zoospores that are produced on the underside of infected leaves) are easily dislodged and spread short distances by water splash and longer distances by air currents (up to 100 miles).
Once a plant has been infected there is no cure. There are preventative fungicides that can be applied by licensed professionals while the plant material is being grown at grower greenhouses. These fungicides have proved affective preventing the disease for short periods of time. Unfortunately, at this time, there are no home sprays for the general public to use.
It is not known how many years the disease may live on in the soil, so good gardening practice is to dispose of the soil, if in containers, and the plants in bags. Please do not add them to your compost pile.
Most reputable garden centers and nurseries will not be carrying Impatiens this year in a cooperative effort to eradicate the disease. â€œObviously, we are not carrying them. It is just too much of a risk to our customersâ€™ gardens,â€ said Bobby Lewis of Meadows Farms Nurseries.
Note that the New Guinea Impatiens (Impatiens hawkeri) are not effected by this disease and are fine for your garden. They can take more sun than Impatiens walleriana and are a bit more expensive as they are tissue-propagated and not grown from seed. They come in more vibrant colors and variegated foliage as well.
Listed here are several choices for adding color to your shade gardens. Part-shade is defined as 3-6 hours of direct sunlight. Full-shade as 3 hours of direct sun or less. Perennials are plants that may die back over the winter, but come back each year. Annuals last for just one growing season.
Impatiens Alternative List
Annuals for Full Shade
Fiber Optic Grass
New Guinea Impatiens
Annuals for Part-Shade
Sweet Potato Vine
Perennials for Full Shade
Aralia Sun King
Heuchera & Heucherella
Perennials for Part-Shade
Dicentra (Bleeding Hearts)
Heuchera and Heucherlla
About the Author:
Kathy is going to miss using Impatiens in her shade-filled back garden, but is looking forward to experimenting with different shade-loving varieties . She is the editor of Washington Gardener Magazine (www.WashingtonGardener.com) and a long-time DC area gardening enthusiast. Kathy can be reached at firstname.lastname@example.org and welcomes your gardening questions.