When people mention heather, they are almost always talking about two different genera of plants: heaths and heathers. Although both belong to the Ericaceae family, they are botanically different and are divided into the Calluna genus and the Erica genus. For practical purposes, however, they are nearly identical, sharing color, form, and growth habits. They are all evergreen, well-mannered, and low-maintenance plants that thrive in similar conditions of sunlight, water, and soil. Winter hardiness is the only major difference between species.
All true heathers are cultivars of just one species, Calluna vulgaris (which some botanists erroneously classify as Erica vulgaris), and there are easily more than 500 varieties available. Most are summer-blooming, ranging from white to rose to deep purple, and their foliage is green to fire orange; their leaves are small and scalelike. Most form low-growing mounds or spreading mats. For the heather lover in the North, these are the plants of choice, as opposed to the true heaths, which offer more colors but are generally less hardy. Calluna are typically hardy in Zones 5-7 but may thrive as far north as Zone 3 with adequate winter protection or snow cover. These low, mounding shrubs are the ling of Scotland, the famous heather of the Highlands.
The true heaths belong to the Erica genus and include more than 700 species and countless cultivars, such as winter heath (Erica carnea), bell heath (Erica cinerea), Darley Dale heath (Erica x darleyensis), Cornish heath (Erica vagans), and cross-leaved heath (Erica tetralix). Hardiness ranges widely; for instance, Erica carnea will bloom under snow, but many of the South African varieties, such as blood-red heath (Erica cruenta), are best left to the greenhouse and florist trades. The true heaths offer an amazing range of foliage and bloom color, well beyond the pinks of the heathers; they also come in taller shrub forms and even some small trees. With hundreds of species and cultivars suitable for hardiness Zones 7-9 or 10 (and a few, such as Erica carnea, even hardier), the heaths provide a wide variety of colors and bloom times to fill Southern gardens.
Other than heaths' greater susceptibility to cold weather, the main difference between heaths and heathers is that heaths have needlelike leaves rather than flat leaves. The scalelike leaves of heather, in fact, feature tiny hairs, which give the foliage a grayish cast. Calluna cultivars also produce blooms where the corolla (or whorl of petals) is completely encased by the calyx (the usually green "leaves" directly beneath a bloom); the Erica species and varieties feature prominent corollas and small calyxes, which often create a two-tone effect to the blooms. However, the bloom shapes are so nearly the same, says Kate Herrick of Rock Spray Nursery in Truro, Massachusetts, "that only a botanist or a true fanatic will know the difference."
Of course, the real reason to plant heath or heather is the colorful bloom and foliage. Imagine Monet's palette loaded with hues of blue, yellow, gold, rose, and green. Imagine a painting built from brush strokes of tall shrubs, lush mounds, and spreading mats. Plant different types of heathers and heaths, and you can have a steady play of form and color as new plants come into bloom when others fade. Plant several varieties en masse on a slope, and an Impressionist's landscape bursts into vivid life.
As heather fans know, selecting plants by color isn't as simple as deciding you like pink blooms; selection by bloom color is actually secondary to the foliage display. A heather's evergreen foliage changes and intensifies in hue during cold weather. For example, Calluna vulgaris 'Firefly' has copper foliage in summer that changes to brick red in winter; Erica x watsonii 'Dawn' (a Watson's heath) has red spring growth that turns to gold later in the year. It is this variability that makes heaths and heathers such arresting plants for the landscape.
"There are so many colors available that selecting plants can be intimidating, and people often make the process more complicated than needed," Herrick says. The colors are so harmonious, however, that a homeowner should pay more attention to plant sizes and spacing, she advises. Selecting plants that will fill a designated space is easier to achieve than trying to work a plant of every bloom and foliage color into the scheme.
"They are a fascinating family of plants," Herrick sums up, "and a lot more fun than red geraniums." Try painting some into your landscape this fall.