When Ken Hensch looks around his greenhouse this spring, it looks a little different.
The wholesale grower usually has about five benches filled with impatiens, popular with area gardeners as a container and bedding plant
This year, we’re only growing one bench, says Hensch, an owner of Hensch Bros. Greenhouses and Aesthetic Plant Specialists in Fort Wayne. We can get them, but there’s no guarantee they would be healthy.
The culprit is downy mildew, a fungal disease that’s been devastating the species known as impatiens walleriana and will likely limit the supply of the colorful, shade-tolerant annuals. The situation has left gardeners and growers scrambling for alternatives.
This issue is a real nasty one, says Ricky Kemery, horticulture educator for Purdue University’s Allen County Extension. There’s no good control to put on the plants, and a lot of places probably aren’t going to sell them anymore.
According to a fact sheet for growers produced by Ball State University, downy mildew was first spotted on impatiens in greenhouses in 2004. But, by 2012, outbreaks in ordinary gardens had been documented in 33 states, including Indiana, Michigan and Ohio.
The disease stunts growth, and plants’ leaves yellow, wither and drop off. Then, even the stems turn to mush. The tell-tale sign is a fluffy, white substance on the underside of leaves.
Kemery says the spread of the disease was likely aided when diseased plants were shipped from large growers to retailers throughout the country. Downy mildew is spread by spores, tiny microscopic particles that can travel through water and air – perhaps hundreds of miles by the latter route, according to the fact sheet.
More insidious, spores also can be spread through contaminated soil and plant containers. And what’s even more troubling, Kemery says, is that spores can overwinter in the soil.
That means that if plants become infected, that soil will just reinfect impatiens planted there next year – and most likely longer, he says.
In the greenhouses, they know what to do about mildew, but the problem is when you get the plant out in the landscape and plants go down, he says. As a result, some horticulturalists are advising that people not plant impatiens at all.
However, some cultivation methods are relatively safer, Kemery says, including growing your own impatiens from seed – seed doesn’t spread the spores – or planting impatiens only in containers in clean soil.
But that doesn’t mean the plants won’t eventually fall victim to spores already floating in the air, he says.
Local garden centers this spring are taking differing approaches to the species.
At Stuckey’s Greenhouses in Fort Wayne, known for large-scale selling of hanging plastic-sleeve planters and other container gardens using impatiens, grower Mark Stuckey says he’s stocking impatiens as he normally would.
The business lost a considerable number of plants to downy mildew last year, he says. We saw it in a week and got rid of it, he says. It caused us to be more aware, to watch for it real closely.
Staff members will do their best not to sell any diseased plants, Stuckey adds.
Doug Hackbarth, owner of Broadview Florists in Fort Wayne, says his impatiens supplier in Toledo has cut back on the number of impatiens being produced. He expects to have an adequate supply, but notes that sales may be dicey because of fears the plants will die.
Hackbarth says consumers should be aware that plants are treated with fungicide prior to shipping. But the pesticide doesn’t last indefinitely, he says, and after it wears out, the public is on their own.
He says consumers should be wary of planting impatiens in the same spot if their plants died last year. With last summer’s drought, many people thought lack of water killed the plants, and not the disease.
Plants probably won’t show downy mildew while the weather is hot and dry, Hackbarth says. But if weather is cool and damp, the signs pop up. Last year, he says, that caused impatiens to die off toward fall.
Hensch, meanwhile, is banking on hybrid impatiens for the containers he supplies to public areas such as Jefferson Pointe. They’re sturdier and more vigorous, and supposedly not as susceptible to this mildew disease, he says.
Consumers can look for the SunPatiens label and a variety called New Guinea impatiens, he says.
They tend to be a bit more upright than regular impatiens and generally have bigger blooms, and their color palette is slightly different than regular impatiens, Hensch says. I’ve yet to see a good white one, he says.
The hybrids can cost up to five times more than regular impatiens, and they have different watering requirements.
They don’t need much water at the outset, and in fact too much water then will make their stems rot.
But, once they get established, expect to water them more often than regular impatiens, Kemery says. If you put (hybrids) in a hot, dry place, they’ll need so much water they’ll make your head spin, he says.
While downy mildew is apparently species specific, Kemery says – air-borne or in-ground spores won’t affect other bedding plants – there’s no guarantee other kinds of impatiens won’t eventually succumb if spores are prevalent.
It’s just another case where you have a disease or an insect that’s come in, like the emerald ash borer, and affecting another common plant that we use all the time, Kemery says. It’s the last thing we need.