Do you love planting impatiens, those bright, velvety annuals that seem to be found around every other suburban tree each spring?
If so, you may need to find an alternative this year, and for a few years to come. A killer fungus is destroying these popular shade loving plants faster than greenhouses can grow them. As a result, many garden centers are pulling them from their inventory.
A vicious strain of downy mildew has been plaguing the Impatiens walleriana population since at least 2011, and growing worse over the last couple of seasons. Horticulturists estimate that the saleable stock of the plants in the U.S. and Canada may be down by as much as 45% this summer, and many of those that are sold may still ultimately succumb to the disease, which lingers in the soil from year to year.
Downy mildew (Plasmopara obducens) is actually a type of mold that thrives in cool, damp conditions. It first appears on the undersides of leaves as a light, fuzzy coating of spores (thus the descriptor “downy”). Because the early stages of the mold’s development are easy for gardeners to miss, plants are usually too far gone to save by time it’s discovered.
The disease can spread in one of two ways: through the air, via the spores, and through infected soil. The disease gets into the soil through the stems of infected plants and can live through the winter.
What to Do if You’ve Had Infected Impatiens
If you planted impatiens in the last couple of years, only to have them mysteriously die off, you may have contracted downy mildew. You’ll need to treat your soil with a soil fungicide before growing more impatiens in that soil — the disease does not affect other varieties of plants.
If you’ve planted impatiens this year, you may not notice signs of downy mildew until later in the season — late June or beyond. If you do start to lose your impatiens, do not compost them or allow them to decompose in place. Dig up all diseased plants, seal them in an airtight bag, and throw them in the trash. Using infected plants in compost will allow the disease to spread.
Alternatives to Impatiens
If you’re a die-hard impatiens lover who is distressed over their sudden scarcity, there are some alternatives.
Torenia (wishbone flower), wax begonias, coleus, hostas, and bleeding heart are all viable options to fill that empty space in your garden this spring.
While it’s always painful to lose an old standby, enterprising growers could view this impatiens plague as an opportunity to branch out and add new colors and shapes to their ornamental gardens.