The bad news first.
Impatiens — the beloved bedding plant, the darling of dappled shade — continue to be dogged by downy mildew disease.
Even plants that look healthy when you buy them at the garden center can become infected several weeks to months later and present the telltale symptoms, including yellowing or curling leaves, blossom drop and stunted growth.
The disfiguring spores of this mold travel through water and air, and once the soil in a flowerbed is contaminated, downy mildew can persist for eight to 10 years. Fungicides have proven ineffective against this plant pathogen.
But there is good news.
There are disease-resistant impatiens for those who can’t let go of the popular plants that fill shady spots with bright, consistent color. Bounce, an interspecific hybrid, provides the traditional horizontal habit that impatiens are prized for, growing knee-high in Northern gardens. And, as its name implies, the plant bounces back if you miss a watering or two.
Lew Gerten of Gerten’s Greenhouses is “really impressed” with the new Impatiens Sun Harmony Series, which he describes as shade-tolerant and free-flowering with a semi-upright, mounding habit.
Of course, lots of landscape experts confess a secret distaste for the ubiquitous impatiens. While they never applaud diseases in plants, some say they hope downy mildew will encourage gardeners to step out of their floral comfort zone and discover new colors, shapes and textures for their shady spots. Here are annual alternatives to impatiens:
• New Guinea impatiens: While they’re not threatened by downy mildew, their more upright growth habit makes them less suitable for bedding areas, some gardeners find.
• Torenia: Sometimes called wishbone or clown flower, torenia flowers resemble tiny snapdragons. They come in blue, purple, pink, yellow and white and have throats splotched with contrasting color. Hummingbirds like them, too.
• Polka-dot plant: Many garden centers are now promoting this popular houseplant as a substitute for impatiens. The adorable, fast-growing plant boasts candy-pink polka dots and a tolerance for heat and humidity.
• Coleus: This vigorous, easy-growing plant comes in countless variations of pink, wine, chartreuse and even deep purples and sunset tones.
• Strobilanthes: Who needs flowers with Persian shield’s almost metallic purple leaves? This foliage plant also can be enjoyed indoors as a houseplant during winter.
• Browallia: The pretty blue-purple flowers and bright green foliage of heat-tolerant browallia form a mounding habit.
• Caladiums: The fancy foliage of caladiums draws a lot attention. The large heart-shaped leaves come in shades of white, pink, red and green. They’re striking in gardens as well as containers and window boxes.
• Alteranthera: Also known as Joseph’s coat, this low-maintenance plant sports colorful foliage. Partytime rocks shocking pink with contrasting green, Red Threads has finely cut, reddish-purple leaves and Little Ruby boasts smaller, rounded ruby-colored leaves.
• Nicotiana: While this well-loved plant can be leggy, there are shorter varieties available, such as Eau de Cologne, which offers a sweet fragrance as well as a more compact size. Star-shaped nicotiana blooms come in rose, pink, white and pale green.
If you’re rethinking your choices of made-for-the-shade annuals, you might want to consider rethinking annuals altogether and put in perennials instead.
Corydalis is a beautiful blooming alternative. Related to bleeding hearts, its fern-like foliage and clusters of yellow flowers make it a charming woodland perennial. There also are new cultivars of heucheras, tiarellas, hostas and ferns that can provide reliable color throughout the season with foliage alone.
The first year you plant any of these perennials, you can get a twofer: Use them as annual container plants in the summer, then plant them in the shade garden come fall.
Rhonda Hayes is a Minneapolis-based garden writer. She blogs at www.thegardenbuzz.com.