Delightful in spring when the frilly white to pink flowers cloak a woodland garden's floor, foamflower (Tiarella spp.) spreads to form an attractively leafed ground cover. Modern hybrids of foamflower boast more colorful or uniquely shaped leaves, making these perennials great for temperate-zoned landscapes. Winter hardiness ranges per species, but these plants need a distinct chilly to cold winter dormancy.
Seven species of foamflowers exist in the wild, growing naturally in woodlands and stream banks in temperate eastern Asia and across central and northern North America.
Four of the five species that constitute the core of ornamental foamflower garden species hail from North America. From the eastern United States and Canada is Tiarella cordifolia. America's Appalachian Mountains are home to the species Tiarella wherryi. Western North American brings us Tiarella unifoliata and Tiarella trifoliata. The Asian Himalayan forests yield Tiarella polyphylla. Hybridization between and among these five species provides dozens of cultivars, cultivated varieties, selected by man.
Growing from underground stems called rhizomes, foamflowers go dormant in winter. In spring basal clumps of stems topped with leaves with an oval to heart shape appear, generally green to yellow-green. Some leaves bear toothed edges and others carry three or five lobes. In the cooler autumn days, the leaves blush attractive tones of gold, orange, salmon, bronze and copper before dying to the ground. In late spring to early summer, delicate upright flower spikes jet up from the foliage clumps and reveal many tiny star-like blossoms of white or pink. Collectively, all these flowers and spikes resemble water foam atop a carpet of green leaves.
Tolerating a wide array of soil conditions, foamflower prospers when soils remain moist and cool. In the woodland setting, partial shade conditions expose plants to shifting dappled sunlight across the day. Brightly colored foliage selections tend to diminish their color if shade becomes too deep. Soil should have lots of organic matter in the soil for lush growth. Foamflowers should not be planted in soils or regions known to experience excessively wet winter conditions.
A "must have" for any shady garden, clumps and drifting masses of foamflowers are used in a woodland garden or in the foreground as edging in a mixed perennial or shrub border. Foamflowers visually complement the foliage textures and colors of hostas, columbines, coral bells, violets and ferns. Foamflowers also may be grown in containers to brighten shaded corners of a deck or porch where traditional sun-loving annuals fail to produce flowers.
When the growing season remains uncommonly humid and rainy, rust may form on the foliage, exacerbated by warmth and lack of air circulation. Slugs relish the foliage and remain a perennial nuisance and destroyer of foamflowers.