Merry yuletide to all.
I am drinking a leisurely coffee, too replete to want even another cookie, and using the Boxing Day respite to think about one of the toughest problems in recommending native plants to replace invasives: ground covers for shade.
The standard list of ground covers for shade includes some of the greatest threats to forest biodiversity conventional horticulture offers. And when you come to think about, that’s predictable. Anything that can suppress weeds (one of the great selling points for ground covers) can surely suppress hepaticas and trilliums, and the other choice but slow-growing gems of the forest floor in eastern North America.
Many of the commoner ground-covers are touted as evergreen – think pachysandra, English ivy, periwinkle – and that is part of their appeal to the gardener. In my part of the world, low native evergreen for shade aren’t that plentiful. (There are more choices where the soil is acidic.) However, it eventually becomes clear to the more experienced gardener that the evergreen properties of the standard ground covers are more selling points than fact. In the areas of southern Ontario where snow cover is unpredictable and comes and goes over the winter, the so called evergreen ground covers look pretty darn shabby by March, and you might wish they were decently deciduous so you could clean them up easily. This took years for me to learn, so powerful is the appeal of “evergreen”, and the combined brainwashing effect of wishful thinking, catalogue descriptions, and the accounts of legendary British horticulturalists. A once-a-decade winter where the snow came early and lasted left the snow-protected leaves of, say, European ginger, looking quite acceptable in late winter, and the self-deception was maintained. It took years for me to figure out that the winters that the leaves look good are the winters that you cannot actually see them.
Beyond “evergreen”, the other stumbling block is the use of ground covers in big single species masses. That too is a big part of their appeal. The garden looks intentional and orderly, and one can make a good argument that the visual quietness of a homogenous area sets off specimen plants, or scuplture, and allows the gardener to play with interesting gardenworthy aesthetic effects. Homogeneity also simplifies rote maintenance enormously. The problem in promoting natives for ground covering purposes is that most native forest-floor species live in communities and assemblages, not homogenous masses. Maintaining an assemblage of species requires a knowledgeable gardener; it is not a task one can entrust to a mow-and-blow service. The good news is, if you get the assemblage right for your garden site, your little native mini-community will do a great deal of the maintenance for itself.
Not all of the maintenance though. Stepping back and saying “They are native – they can look after themselves” will quickly leading to the establishment of a thicket of invasive woody saplings. (That’s why they are invasive – they out-compete natives.) So there is no getting around the fact that natives will require more maintenance than the all-smothering standards. However, most of the maintenance should be in the form of knowledgeable attentiveness, not actual work.
That said, there are natives one can coax into growing in single-species masses, there are a few evergreen choices for near neutral soils, there are delightful ways of layering spring ephemerals with more lasting companions, and other ways of finding garden worthy substitutes for invasive alien ground covers. I’ll explore a few possibilities in future posts this winter.