Not A Time To Be Impatiens

If you’re like most gardeners, you either grow or have grown the most popular bedding plant in America:

impatiens walleriana

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This is the species that usually comes to mind when we talk about garden impatiens. They’ve been inexpensive, come in a wide range of colors, tolerate a great deal of shade, give great garden coverage when properly planted and, according to one botanical garden website, “have no serious disease problems.”

Well, there’s trouble in paradise. Lots of trouble.

These impatiens may be very hard to find this year. And if you do find them, you may want to think twice before planting them.

Right about now wholesale growers would normally be filling up their greenhouses with hundreds of millions of these plants in the form of seedlings or tiny plugs. But this year there will be hundreds of millions fewer as growers, landscapers, landscape designers, garden centers and home gardeners try to figure out what can be used as a substitute.

These impatiens have been a critical part of gardens, baskets and planters where sun is an issue and bright color is required as part of the garden scheme. This year, creativity and horticultural wisdom are going to be taxed to fill the void.

The problem is IDM, or impatiens downy mildew, a fungus going by the name of “plasmopara obducens.” For now it’s affecting only the walleriana species, so if you’re using the New Guinea types, which prefer more sun, or the newer SunPatiens hybrids, which tolerate even more sun, you’ve got no problem. But for the impatiens that do well in the shade, our luck may be running out, or it might have already run out.

The disease first showed in the U.K. in 2003. It then travelled to California in 2004. It hit the East Coast in 2009 but at that time it was somewhat isolated. Then in 2011 and 2012 it crossed the country, showing up from California to New York and as many as 10 other states.

The symptoms start with a few leaves that discolor and turn yellow. Yellow leaves can also be caused by fertilizer issues and who has never, ever grown impatiens where some leaves yellow and fall off?

With IDM though, the foliage then begins to curl and the plant looks like it’s wilting from a lack of water, even though that isn’t the case. At this point you can use a magnifying glass to look at the undersides of the leaves and you can start to see the tiny spores.

In as little as one to three days the leaves and flowers drop, leaving only the stems. Even the bare stems become affected as they become soft and the plant collapses.

The problem was widespread on the East End last summer, and as the season matured the problem became worse. I remembering visiting one garden center on a Wednesday when a shipment of impatiens came in. There were dozens and dozens of flats that would go into local gardens that weekend. By Friday, the entire shipment was pulled from the benches as just 72 hours after delivery the plants were unsalable.

Being a fungus, this disease is spread by spores and spores love and need moisture as part of their reproductive process. What better place for this to take place than in a shaded, moist environment—just where this species of impatiens grows best. Add a little bit of overhead irrigation, some splashing and a little wind and you’ve got the perfect combination of elements for this disease to become rampant.

Ah, but there’s more. There always is.

This disease has two types of spores. The second type, referred to as “resting spores” are produced inside the stem of the plant and parts of the leaves. These survival spores then drop to the ground with the dying plant debris, where they may survive for as long as five years, just waiting for the opportunity to infect the next batch of impatiens that you plant. So, once you’ve had this disease on your property there’s a very good likelihood that any impatiens of this variety (ONLY) will become infected.

If you didn’t have the problem last year and you plant perfectly clean and disease-free impatiens this year, the spores can still blow in from your neighbor’s garden. And remember that little breeze we had last fall by the name of Sandy?

So what’s a gardener to do? First, and most important, remember and tell everyone that this disease affects only impatiens walleriana—the common bedding impatiens. The double-flowered impatiens also belong in this group, as do the dwarfs or minis. While IDM may infect the wild varieties, known as “jewelweed,” we don’t think it’s devastating to that plant, just a nuisance.

Other impatiens, including the New Guineas, which have long and pointed leaves not short and rounded, and the new SunPatiens are not affected and can be planted without fear of the disease.

Second, if you had this issue in your garden last summer, or if you even suspect you had the fungus on your property, it’s probably not a good idea to plant these impatiens this year. The availability will be limited anyway and even if they come from an allegedly clean source, there’s the very real possibility that you’ll have to deal with the fungus this summer or in the near future.

I suspect that the big-box discounters may carry them this year but local garden centers who rely on your loyalty will be much more conservative. If you feel lucky, limit your planting. If you’re smart, find alternatives.

Third, speaking of alternatives ... Yes the choices for annuals that will do well in the shade are very limited but we’re all in the same boat and everyone is looking for new plant combinations and possibilities.

The first choice that comes out of everyone’s mouth is the bedding begonia, but this plant doesn’t come anywhere near the versatility of impatiens. A less common but interesting plant is torenia fournieri, or the wishbone plant.

There are also the coleus and I’ve seen some magnificent plantings of this annual over the past few summers. It’s a different plant with different characteristics but some do very well in shade, offering slightly taller plants with different textures and colors. The colocacias and alocacias also offer an alternative for shade planting but these can get fairly large and make a very different statement than the short and sweet impatiens.

Caladiums offer a possibility as well. With the dwarf and taller varieties, this bulb creates a wide range of foliage colors and textures that do really well in the shade and they just soak up the heat during the dog days of summer. Caladiums can be started early indoors then bedded out or purchased as potted plants at garden centers.

I think this plant offers some real opportunity, and in future summers I think the prices will come down, breeding will increase and we’ll find this to be a very common shade garden plant. Also, don’t overlook the fact that caladium bulbs can be dug at the end of the season and stored for use again the following year. With well over 50 varieties available at less than 50 cents per bulb in bulk they can be an interesting and eye-catching alternative to impatiens in shady areas.

I expect more news about the impatiens problem later this month and as we head into spring and summer. We already know it’s present right now in Florida and I have every reason to believe that it will migrate north with the wind and the south-to-north growing pattern of the bedding plant industry.

Be cautious. Don’t depend on the walleriana species for critical garden elements. On the bright side, here’s a true chance for the creative and thoughtful gardeners to shine and teach us all. Keep growing.