Impatiens are the very best annual for abundant color in the shaded garden.
Big blooms cover low, mounded plants and offer an incredible range of hues, just about every color in the rainbow except a true blue. Plants will perform and bloom well in full sun if soils are consistently moist, but shade is where they shine — no other plant can provide the same reliable, profuse flowering display.
These are the classic Impatiens walleriana, not the fancy New Guinea impatiens or SunPatiens that have been filling the greenhouse benches. Common names include busy Lizzy, sultana, patience plant and touch-me-not, though most of us know them simply as impatiens. They have fallen out of favor in recent years, but may well be on the verge of a comeback.
It was August 2012 when impatiens downy mildew (IDM) disease decimated impatiens plants in gardens across the country, including
Michigan, including mine. The disease acts quickly, seemingly overnight turning healthy blooming plants to sickly stems with just a few clinging yellowed leaves. Like other downy mildew diseases, IDM is in the soil, and is spread when water splashes it up on plant leaves. The right combination of plant stress, humidity and temperature will awaken the mildew and it infects the plants. It likely started with the plant supply and spread to gardens where plants were grown.
The only effective treatment is prevention, since impatiens are annuals and would not have time to recover and regrow before the season was over.
Over the past seven years, the impatiens selection has been limited in garden centers.
Growers must be extra vigilant to keep their crop healthy, and the preventive fungicide treatments are expensive — yet it’s not feasible to charge more for a flat of impatiens when the risk doesn’t end once the plants are in the garden. And I, for one, was no longer willing to invest the time, effort and money to fill my shaded gardens with flats of impatiens that could die by midsummer.
Fortunately, we haven’t had another perfect storm since the summer of 2012. IDM is still around, but it has appeared sporadically, without another dramatic, widespread outbreak. Many gardeners have adapted their selection of annual shade plants to adjust for the reduced supply of impatiens, and perhaps even forgot about the disease issue, if they ever really knew the details of what happened.
Not only were impatiens staples of the shaded garden, they were a profitable commodity for the horticulture industry, for home gardens and commercial landscaping. Plant breeders shifted their efforts to developing varieties of impatiens with resistance to IDM.
Two of the biggest seed companies, PanAmerican Seed (part of Ball Horticulture) and Syngenta flowers are introducing resistant series for the coming season. I’m sure that supplies will be limited, but I will be on the lookout for them during my spring plant shopping excursions.
Imara is Syngenta’s introduction — and it may also be sold as Imara XDR (for eXtra Disease Resistant). Available in a mix and six individual colors; rose, white, red, orange, violet and orange star. Plants form uniform, mounded plants with a 10- to 12-inch height and spread.
PanAmerican is offering the Beacon series. Plants have improved vigor over their long-standing Super Elfin series, and of course very high resistance to IDM. Offered in violet shades, bright red, coral, orange, salmon, white and two mixes; red/white and a complete mix. Upright-mounded plants grow 10 to 12 inches tall and 12 to 14 inches wide, with recommended spacing of 8 to 10 inches.
It looks like our favorite shade annual is on its way back.