The culprit in this gloomy scenario is well-known in the trade and virtually unknown to consumers: downy mildew, a deadly, fungus-like disease that targets the popular garden plant known as Impatiens walleriana.
In 2011, the disease was confirmed in 11 states. In 2012, it was in 34, including Pennsylvania and New Jersey. The damage this year is anybody's guess, but there's no question there will be damage.
"The feeling is, it's really going to be pretty much everywhere," says James Harbage, research and production leader at Longwood Gardens in Kennett Square.
The news is devastating for gardeners like Myrna Pope.
Over the last 30 years, she has planted thousands of impatiens on her shady 1.5-acre property bordering the Wissahickon in Chestnut Hill. Living without them is unthinkable.
"I'd be hysterical!" she says.
Once the plant is infected by the mildew spores - found in soil, water, and winds from as far away as a hundred miles - small yellow spots appear on the tops of the leaves and fluffy white-gray growths on the undersides.
There's no cure, and no affordable, foolproof way to forestall the end. The plant shrivels and dies in a matter of days or weeks, while the offending spores can live on in the soil for a year or two or more.
Cool temperatures, high humidity, and moisture from rain and overhead sprinklers or irrigation systems fuel the spread of the disease. And spores in the ground can survive the winter.
"They've figured it out. During dormancy, they form a very thick-walled spore that's resistant to cold and flooding and drought," says Gary W. Moorman, Pennsylvania State University plant pathologist. He believes that the downy mildew problem could cripple impatiens production and sales for years.
"This is a real big problem. We would not recommend any home gardeners buy impatiens," says Ken Ruch, president of George Didden Greenhouses in Hatfield, a fourth-generation, family-owned wholesale grower. More than $40 million worth of impatiens are sold nationwide annually; they're 15 percent of Ruch's springtime sales, and it's been that way for at least 30 years.
At a seminar he's hosting this month for his landscaper and garden center clients, Ruch says he will "strongly discourage" them from selling impatiens. He will suggest alternatives, such as New Guinea impatiens and SunPatiens, two types that are not susceptible to downy mildew, along with begonias, coleus, and caladiums.
Didden's will be growing some traditional impatiens for those who ignore the warnings. He likens them to "people who come in on April 1 and insist on buying a tomato plant. You just can't talk them out of it."
But Dave Scott, owner of Laurel Oak Garden Center in Marlton, won't sell regular impatiens this year. He'll be promoting other options, though he thinks it'll be a tough sell.
Begonias, for example, are worthy shade plants, but don't have the flower power of impatiens. Coleus and caladiums have delightful foliage but unremarkable flowers.
Some gardeners have issues with the other impatiens. New Guineas are beautiful, but are sold in larger pots, rather than flats, so they'll cost more - and they don't spread as well as their popular counterparts.
SunPatiens were bred for heat and sun, which won't do for shade customers, according to Bruce Albrecht of Albrecht Nursery in Narberth.
"We have a lot of properties on the Main Line that are older and established, with a lot of shade, and there's nothing like impatiens for shade," he says.
Recognizing that, Home Depot will sell impatiens this year. But, says Dan Stuppiello, who oversees plant sales at stores in the Northeastern United States, including the Philadelphia/South Jersey region, Home Depot's growers are "taking extra precautions" to make sure the plants are healthy when they leave the greenhouse.
Stuppiello acknowledges that that is no guarantee those plants won't get downy mildew later on, so sales associates "will also be telling our customers, 'Listen, there are some great alternatives out there that do just as well.' "
Longwood Gardens, which typically uses 1,500 traditional impatiens each spring, has already gone the alternative route. Last summer, beds were planted with New Guineas and SunPatiens instead. (Longwood funded and was part of the plant-collecting trip to New Guinea that brought that impatiens variety to the American market in 1970.)
"Within what's available right now, they're the best alternatives for actual ground beds," Harbage says, although he believes traditional impatiens planted in containers or hanging baskets might be safe from downy mildew.
The threat likely will continue apace until breeders find a resistant variety that looks and behaves like I. walleriana, which is so common it's sometimes derisively called "the gas station plant."
But the breeding process - and scientific vetting of the disease - will take a while. "I think this is going to be measured in decades rather than years," says Margery Daughtrey, plant pathologist at Cornell University's Long Island Horticultural Research and Extension Center, who is studying downy mildew.
In the meantime, Joseph G. Marano, Jr., manager of Marano's Gardens in Fort Washington, hopes to convince his impatiens-loving customers that downy mildew is real. "Word hasn't really gotten out yet. It's going to be hard for them," he says.
Myrna Pope, a Marano customer, is steeling herself.
"I love impatiens in red and various shades of salmon and white. Been this way for as long as I can remember," she says, "but I guess I'll have to think of something else."
Contact Virginia A. Smith
at 215-854-5720 or email@example.com.