Questions From The Plant Clinic: The Return of Impatiens
The Return of Impatiens
Have you been wondering why you’re starting to see impatiens at the store again? Master Gardener Volunteer Carol was too, and did some research to find out why! Read more articles from our Master Gardener Volunteers [here].
Beautiful traditional impatiens (Impatiens walleriana) used to be a mainstay in Central Florida gardens. Their bright pink, white, red and orange blooms gave a pop of color to plant beds in shaded areas. Considered annuals, their self-seeding ability allowed them to last for many years in the mild climate of Central Florida. Winter temperatures below freezing could kill them but, even then, plants covered to protect them from the cold frequently recovered. They required well drained soil and plenty of moisture during the heat of the summer. Even so, they were generally easy-care plants that bloomed for most of the year.
Downy Mildew Demise
Then in 2011 downy mildew (Plasmopara obducens) disease appeared in Palm Beach County Florida. It proceeded to kill traditional impatiens off across the state. The disease flourishes in climates with high humidity and cool nights, and it was found year-round in south Florida. The pathogen that carries downy mildew is a type of water mold closely related to algae. It spreads using two types of spores, one that can move through water or by wind and the other that can live for years inside plant tissue. While the disease devastated traditional impatiens, New Guinea impatiens survived because it is immune to the disease, as is SunPatiens, a hybrid developed by a Japanese seed company. New Guinea impatiens, however, needs more sun than traditional impatiens and does not bloom all summer and SunPatiens likes full sun so it is of no help to people with shady gardens.
A New Hope for an Old Garden Favorite?
Finally, Pan American Seed has developed a downy mildew resistant variety of traditional impatiens, which they released this fall, and other companies are likely to roll out their own versions this spring. Welcome back to the shaded world of gem like planting beds and bursts of color in pots under oak trees and near doorways.