What’s not to like about Impatiens – one of the garden’s most reliable and foolproof plants? This easy-to-grow shade-suited bedding plant sports showy flowers available in a color palette from vibrant to pastel. Commonly called Busy Lizzy, Patient Lucy or Sultana, it’s a nonstop bloomer that grows worldwide, from the tropics to North America’s temperate zones to the Asian and African subtropics.
But as more plant pathologists warn of a downy mildew epidemic that has decimated this member of the Balsaminaceae family since 2011, many landscape designers aren’t fretting that the Impatiens’ popularity is waning. Their comments range from “ . . . ubiquitous, boring and not at all that pretty” to “ . . . withering and wimpy” or “. . . flat, dull . . . looks like it was drawn by a kindergartener.”
Unfortunately, the impatiens’ future is even more uncertain with confirmation of mold spores in 33 states and Washington, D.C., despite wholesale sales figures from the U.S. Department of Agriculture that topped $174 million in 2009. See the Wall Street Journal article, “Impatiens Are Withering, And Some Say It’s About Time.”
What’s the fuss about downy mildew?
Janna Beckerman, a Purdue Extension plant disease specialist, said early symptoms are not always visible, such as white-colored sporulation that mimics spider mite damage. She describes this pathogen as a water mold (Plasmopara obducens) that can develop in three ways:
Most experts agree that by the time a gardener notices the impatiens’ blooms are drooping, a downy mildew outbreak is in full swing, transforming bushy tender-stemmed plants into bare stalks that will soon fall over and die. The consensus is pesticides are ineffective. There is no cure. Composting is contraindicated because this mildew produces two types of spores – short-lived spores that form white down on a leaf’s underside that spreads through rain or wind; and resting spores that infect stems and can winter in the soil, then infect next year’s plants. Instead, gardeners should dig up and bag all diseased plants for trash removal.
How die-hard Impatiens lovers cope
Those who enjoy the impatiens’ easy care nonstop color around homes and commercial landscapes from April until frost are learning to live through this moldy killer’s attacks. We don’t view impatiens as plain, wimpy or overused but as low-maintenance, self-cleaning season-long bloomers. After all, any plant that brightens shade gardens and saves our backs from stooping down to deadhead spent flowers is worth the risk of losing.
But to minimize the potential for downy mildew, we can keep an eye out for symptoms of downy mildew – stunted, curled leaves on new growth and fuzz developing on leaves’ undersides, especially during cooler weather. Since the possibility of the disease increases with moisture, well-draining soil is essential and overhead watering should be avoided so leaves don’t stay wet for long periods. Also, providing space between each plant, instead of jamming them tightly together allows air to circulate. Another preventative strategy is to replace the impatiens with a different bedding plant every other year, much like vegetable growers rotate crops. Finally, by remembering all the reasons why impatiens are one of the most popular annual bedding plant in the U.S. also helps gardeners cope with this deadly pathogen.
A multi-faceted uniqueness
Impatiens is Latin for “impatient” referring to the explosive nature of their ripened seedpods that burst into the air, distributing seeds several feet away. Believed to be natives of Zanzibar, an island off the cost of Tanzania in eastern Africa, impatiens were introduced to the western world in 1896 by a British physician and naturalist, Dr. John Kirk. One variety, Impatiens sultana, was named in honor of the Sultan of Zanzibar with a name change to Impatiens wallereriana following the 1861 travels of Horace Waller, a British missionary and lay superintendent of the Universities Mission to Central Africa. This plant grows to about 3 feet tall and is only one of more than 500 species in the Balsam family (Balsaminaceae). A few are considered weeds and grow up to 7 feet like the Himalayan balsam. Some impatiens are annuals, flowering early summer until frost, while perennial species can flower all year in temperate zones.
Usually, the flowers are flattened in appearance and irregular in shape with five petals and a slender spur. But with the development of hybrids, semi-double and double blooms that resemble roses are also available. Leaves are ovate to elliptic in a light to dark green with an occasional bronze tinge at the tips. In 1969, the U.S. Department of Agriculture funded a plant collecting expedition to New Guinea and found new species with larger flowers and different leaf variegation, hence the release to the public of the New Guinea impatiens with a tolerance for sunlight. Whatever species of impatiens you choose to plant, you’ll be amazed how they jazz up your flowerbeds, hanging baskets and patio pots. A pop of color from just one impatiens goes a long ways.
Launa Herrmann is a Master Gardener with the University of California Cooperative Extension office in Fairfield. If you have gardening questions, call the Master Gardener’s office at 784-1322.