I’m being forced out of my comfort zone this year. Like many shade gardeners, I’ve been over-dependent on impatiens for color, and I’ve been planting the same arrangement of white, pink, lavender-blue and violet impatiens in a bed at the end of a long walkway in my shady garden for a decade or more. But last year the patch came down with downy mildew, a nasty fungus disease that has infested a lot of the greenhouses where impatiens crops are produced. Since the fungus spores persist in the soil, I can’t plant impatiens in that spot this year. It’s time for a new look.
I can safely plant unrelated plants in that bed, because as far as anybody knows this fungus only attacks impatiens. (Vegetable gardeners rotate crops, routinely switch unrelated plants around from year to year to break the cycle of diseases or pests. Why didn’t it ever occur to me to do the same thing with annuals?)
My alternatives for color in the shade start with that old standby coleus. The gaudier varieties, with multicolored spots and blotches and fringed or scalloped leaves, are a taste I haven’t acquired. But I find many uses for more sedate ones, with uncomplicated chartreuse or purply-red foliage. They are great fillers in shady spots.
Chartreuse sweet potato vine is another foliage plant that brightens shade. I’ve often used it in hanging baskets. I also plant a few begonias in pots each year, some for their leaves and some for their flowers, and this is probably my year to broaden my begonia range.
There are other flowering annuals that have some shade tolerance. I’ve had luck with blue torenia and streptocarpus, a charmer with delicate violet-blue flowers that that my stepmother used to call “that whooping cough plant.” But the shade in my garden is too deep for lobelia or fuchsia to keep blooming.
Many shade annuals have the additional virtue that they can be overwintered as houseplants or in a greenhouse. But they’re not the only alternative.
Some shade-tolerant perennials have season long color in their leaves. The obvious example is coral bells, which have been bred with foliage in colors including sickly pale yellow, chartreuse, silver-green, pink, apricot-orange, burgundy, purple and almost black. As with all plants, the most shade-tolerant coral bells are the ones with straightforward plain green leaves, because they have the most chlorophyll for photosynthesis. Plants with less green need more sunlight to make up for it.
I’ll be mixing up all these plants this year. My new plan for the bed at the end of the walk is a collection of pots, surrounded by a perennial groundcover — a silvery lamium, maybe, or wild ginger. With fresh, sterilized potting mix in the containers, maybe I’ll even risk a pot of impatiens.