by Connie Oswald Stofko
If this summer is like last summer in Western New York, you might be able to plant impatiens and have them perform well, perhaps into August, anyway.
But there are still a lot of ifs involved, and there are certainly no guarantees.
Margery Daughtrey, senior extension associate with Cornell University who co-wrote a fact sheet on how downy mildew affects impatiens, gives us an update on what Western New York gardeners might expect from impatiens this year.
Background
Since they were introduced in the 1960s, impatiens has been everybody’s favorite flower for shade. It grows in lovely mounds and gets lots and lots of colorful flowers. The plant is inexpensive, too.
Then a couple years ago, downy mildew started to kill impatiens. There is no treatment that the home gardener can apply.
Last spring we told you about alternative plants for the shade. (Note that although they have similar names, New Guinea impatiens is different from Impatiens walleriana, the plant that is being killed by downy mildew. New Guinea impatiens can be a dependable, although somewhat more expensive, alternative.)
How did impatiens fare in Western New York last year?
In the summer, Cornell University asked our readers for input on how their impatiens were faring and many readers left comments.
Many people who had problems with impatiens in 2012 didn’t plant them at all in 2013.
People who did plant impatiens last year found that the plants, for the most part, were doing well into August, judging from their comments and some chats I had with gardeners.
There seem to be two factors that worked in favor of impatiens last year: the way they were grown in greenhouses and the weather we had, Daughtrey said.
Local growers applied a fungicide to impatiens to keep them healthy while they were being grown in greenhouses. (This isn’t something that a home gardener can apply. There aren’t any treatments that home gardeners can use.) The plants were healthy when they were transplanted into people’s gardens, Daughtrey said, and the fungicide may have protected the plants outside for another month or so.
Wet weather and cool temperatures help the disease thrive and spread. We had a rainy June, but it got drier after that. The fungicide may have protected the plants during the worst of the wet weather, then the hotter, drier weather may have made it more difficult for the disease to proliferate.
The result, Daughtrey said, was that we saw less disease and when disease appeared, it appeared later in the season.
For some people, this is satisfactory. Since we might get a killing frost in September, if the flowers last into August, some gardeners are happy.
“They don’t require that the plants look good into the fall,” she said.
Should you plant impatiens?
First of all, you don’t have to feel guilty if you plant impatiens, Daughtrey said. You’re not hurting the environment.
“I think the disease will always be here– It has always been here,” she said. In books from the 1800s, it was noted that the disease affected a wild plant called jewelweed, which grows in wet areas. The disease is still affecting that wild plant and can come back from those areas.
If you like impatiens and want to try them, go ahead, she said.
But even if they did well in your garden last year, they might not do well this year. There are many factors involved, and even the experts don’t understand it all, Daughtrey said, so they can’t offer simple advice.
“How impatiens performs this year depends to a huge extent on the weather,” she said, and no one can predict now what our summer weather will be like. Wet weather can make the disease worse. Because the disease is linked to weather, we may have years when impatiens do well in our gardens and years when they don’t.
And no, the cold winter we had this year didn’t kill the disease, she said.
The fungicide that growers apply may protect your impatiens for awhile, but then the plants might die.
“So don’t put all your eggs into the impatiens basket,” Daughtrey said. “If you want a pretty garden, bring in other plants. You want a mixture of plants, not a monoculture.”
Gardeners sometimes enjoy a challenge.
“People feel so clever if they can get impatiens to grow,” she said.
Even if you want to try impatiens this year, they may be hard to find. Of the garden centers I work with, the only one that I know will be offering them is Bengert Greenhouses, 230 French Rd., West Seneca.
Tips for getting impatiens to perform well in your garden
If your impatiens gets downy mildew, there is nothing you as a home gardener can do to treat it.
“It’s not something you can outwit,” Daughtrey said. “You can’t go to the store and buy something to spray; there are no tools you can get.”
However, there are a few steps you can take to try to have healthy impatiens in your yard for as long as possible.
The first step is to make sure that you are buying healthy plants. Look at the underside of the leaves. If the underside of the leaf looks white and sugary or white and cottony, that’s a sign of downy mildew. Don’t buy the plant. In fact, point it out to the staff. If you see purple splotches, don’t worry about it– that’s normal. See photos of symptoms of downy mildew in impatiens here.
The greenhouse industry is producing a supply of impatiens that is much healthier, she said. Before you buy plants, ask the staff whether the impatiens plants have been treated with fungicide to protect them from downy mildew.
How you water your impatiens may affect the growth of the disease. The disease likes wet conditions in cool temperatures. The worst weather is when it rains several days in a row without drying out. You can’t prevent that, but you can try not to duplicate those conditions when you water.
Daughtrey knows that so many of us like to come home from work and water our gardens– It’s soothing. But to help prevent disease on your impatiens, you should water in the morning so the foliage has a chance to dry during the day before the temperatures get cool.
Water thoroughly and less often, though she noted that during the summer you may have to water impatiens every day. Do what you can to allow the foliage to dry in between waterings. Don’t withhold water– your impatiens need water to live.
Planting impatiens in containers and setting them on a porch or other area with a roof where they are shielded from rain may help, too. When you water plants in containers, you tend to water the soil rather than spray the leaves, which can help. In addition, impatiens in a hanging basket may benefit from better air circulation.
Why is impatiens being killed by downy mildew?
Experts aren’t sure why impatiens, which was such a dependable plant for decades, is suddenly being killed by downy mildew.
There could be new strains of the disease. Scientists are looking at a physical specimen of the disease from the 1800s that is the same as what we see today at the genus and species level. They’re comparing sequences of DNA to see if they are different at that level, Daughtrey said.
We mentioned before that downy mildew affects the wild jewelweed. It also affects a garden plant called balsam impatiens, Daughtrey said. Balsam impatiens isn’t very common; it’s not big in the bedding plant industry. It’s an old-fashioned plant, an heirloom plant, that some gardeners grow from seed and share with others.
While balsam impatiens is affected by downy mildew, it doesn’t die from downy mildew. It doesn’t even drop its flowers or leaves. It just gets patches on its leaves.
With the popular impatiens that shade gardeners love (impatiens walleriana), the plants will seem fine, then they turn yellow and quickly drop their leaves, drop their flowers and even drop their stems. See the progression of the disease here.
“It’s so much more devastating than the average disease,” Daughtrey said. “That’s why I’m thinking it might be the plant.”
It could be that these impatiens have been bred in a way that accidentally made them susceptible to this disease.
“That would be nice because if it was bred in, we could breed it out again,” she said. If breeders can create a variety of impatiens that resists downy mildew, the resulting plant might not be as spectacular as the impatiens we’ve come to know and love previously. But if it could survive downy mildew, gardeners might be satisfied.
Other plants may be developed to provide colorful flowers for shady gardens. She noted that companies are working hard to develop plants “to make us feel happy like impatiens did.”
Good update, but once in the soil it persists. Always a chance…
Thank you for sharing all this helpful, educational information!