In my BDN post two weeks ago (May 2), I described four woody plants that belong in a small garden designed for all seasons: pagoda dogwood and the ‘Donald Wyman’ crabapple, both small trees, and two flowering shrubs, summersweet clethra and red-vein enkianthus, although the later can be developed into a small tree with careful pruning. This column focuses on four native perennial groundcovers that would thrive in shady areas of the small garden, including beneath the canopy of a small garden tree.
You can find foamflowers (Tiarella cordifolia) growing in small patches along stream banks. They are native to woodlands throughout New England, growing 6 to 8 inches tall and 11 inches wide with slightly hairy heart-shaped leaves and foliage that is often marked with maroon patches. In spring the plants give rise to spikes of starry white or pink flowers that move in a gentle breeze like foam on a sea of green.
Many of the foamflowers found in nurseries and garden centers are varieties developed for their unique foliage color and leaf shape. In Marjorie’s Garden we are growing the white-flowered ‘Running Tapestry,’ its dark green leaves boldly marked by deep maroon veins. We were sold on this evergreen variety when we saw the coppery tones of foliage in early spring as the plants emerged from under the snow.
Foamflowers are easily grown in well-drained soil in partial to full shade. They prefer humus-rich, moisture-retentive soil that does not dry out; wet soils, particularly in winter, can be fatal. You may want to remove the spent flower stalks after the blooming period to fully enjoy the summer foliage.
Tiarella spreads vegetatively by runners, so a handful of plants purchased at the nursery will, in a few years, cover the ground beneath the canopy of a garden tree. One of our favorite scenes in the spring garden is the sea of foamflowers that flows beneath the branches of a white fringetree (Chionanthus virginicus).
Natural colonies of Canada mayflower (Maianthemum canadense) grow throughout New England. In Marjorie’s Garden, their glossy green oval leaves soak up dappled sun beneath white pines and spruces. They seem to thrive in the thin acidic soils beneath these trees. Growing from 3 to 6 inches tall, the plants in some colonies have mostly infertile shoots and seldom flower, while those in other colonies send up 2-inch-high flowering stalks each May, the tiny white flowers arranged in pairs along the stalks on slender pedicels. Small native bees collect pollen from the fragrant flowers.
The flowers are followed by quarter-inch round berries, green at first, speckled pale red at maturity. These berries are eaten by ruffed grouse, white-footed mice, and chipmunks, all of which help spread the seed around.
Starflowers (Trientalis borealis), dainty plants rising only 4 to 8 inches from the ground, are always a joy to find blooming in Marjorie’s Garden during May. They often mingle with the Canada mayflowers, developing open colonies from slender rhizomes. The star-shaped white flowers, about one-half inch across, frequently have seven petals, but sometimes as few as five or as many as ten. While tolerant of thin acidic soils, they also thrive in cool wooded areas with peaty soils.
Many New England gardeners are lucky to have starflowers as part of the native flora in their garden. They can, however, be planted. The New England Wildflower Society (Framingham, Massachusetts) recommends transplanting seed-germinated plants from containers in spring or planting dormant rhizomes into a moist acidic soil in late summer.
When asked to recommend a native groundcover for a shady site, I often encourage the gardener to plant more than one shade-tolerant species. Growing conditions at the base of a garden tree will vary from spot to spot, influenced by the extent of competition for water and nutrients and by the amount of sunlight received during the day, so it is unlikely that a single plant species will carpet an extensive area. We can mimic what happens in nature and plant a tapestry of Canada mayflower and starflower, a combination often seen in the wild.
Growing only a few inches high, bunchberry (Cornus canadensis), a native dogwood, is one of several companion plants of mossy areas. It colonizes small niches where the moss languishes to create a tapestry of colors and textures. Like its tree-form relatives, the flowers of this dogwood are in tiny white clusters surrounded by four large bracts, giving the appearance of a single blossom. The fruits, borne in clusters (or bunches, as indicated by the common name), are coral red.
Many New England gardeners are lucky to have bunchberry growing wild on their property, often in the garden proper. It grows most vigorously in partial shade, preferring soils that are moist but well drained and acidic.
Take a walk through a local wooded area with an eye to the ground and you are likely to find combinations of bunchberry, lowbush blueberry (Vaccinium angustifolium), and ferns. Here the bunchberry will thrive, there the blueberry, and so on, each species occupying the spots most suitable to its needs.