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Colorful Native Shrubs and Trees for Acidic Soil

Leucothoe axillaris 'Curly Red'

Leucothoe axillaris 'Curly Red'

Text by Max Eber for the November/December 2016 issue of Horticulture.

The heath family, Ericaceae, is a jewel box of species much beloved and used by gardeners. Native to a wide range of habitats from heathlands, bogs, moist forests to pine barrens, they can supply a firm design backbone for gardens with difficult situations, with generally one unifying requirement: acidic soil. Like Tiffany jewelry, these plants carry a design theme: waxy pendulous bell- or trumpet-like flowers. The trees and shrubs often have evergreen or semi-evergreen tendencies; the deciduous relations often show rich fall colors.

If your soil is acidic, you probably have one or two such gems in your garden already. Ericaceae boasts claim to not only small, shrubby heathers—the summer-blooming Calluna and winter-blooming Erica species—but also the garden’s hard hitters, such as Rhododendron (thus, also azaleas), Kalmia (mountain laurel), Pieris (known commonly as andromeda in North America), the former Menziesia, (now a part of Rhododendron) and important economic edible crops from Vaccinium (cranberries, blueberries, huckleberries and more) and Gaultheria (wintergreen).

Indeed, many of North America’s showiest and most lucrative native contributions to the garden trade come from Ericaceae. The following are a few of those native gems that showcase the family’s flexibility. They are unique species—one an old standout and three new garden classics—all becoming more widely used in landscapes alongside their more famous cousins. Accordingly so, when happy they never fail to impress.

Bog rosemary
Members of the genus Pieris are often referred to as andromeda, but there is in fact a sole true Andromeda species: Andromeda polifolia, or bog rosemary. The only member of its genus, this northern North America native resembles both heather and the unrelated herb rosemary, with spikey blue-green leaves creeping in mounds 5 to 18 inches tall and wide. ‘Blue Ice’ is the chosen variety, a rather dwarf selection with bright powder blue leaves and pink Vaccinium-like flowers in spring. Bog rosemary prefers sandy, peaty soil and moist, cool conditions. Give it a spot in part-shade to sunny rock gardens and bogs. Extremely cold hardy, it survives USDA Hardiness Zones 2 to 8.

One of the largest of Ericaceae, Oxydendrum arboreum, or sourwood, is a multi-season dream of a tree. It’s absolutely unique, a hand-fashioned gem, being endemic to the Mid-Atlantic and Southeast, with no equivalents or relatives elsewhere in the world. Sourwood remains a small- to medium-size tree in cultivation, growing at a moderate rate to a height of 20 or 30 feet and a pyramidal spread of 15 to 20 feet. It can be long-lived, reaching ages of 80 years or more.

Sourwood bears luxurious green, oblong leaves, four to eight inches long, that give it a languid peach-tree look. In midsummer, long panicles of small, white lily-of-the-valley blooms further the tree’s fountain-like appearance, much like an oversized Pieris. These highly fragrant flowers serve as an important nectar source for beneficial pollinators and make incomparable honey and jellies. Flower panicles and tan capsules cling to tree even after flowers drop, contrasting against the bright scarlet foliage brought on by cooler temperatures in fall. Sourwood is generally a disease-free masterpiece with varied uses and high wildlife value, but it is intolerant of heavy pollution. It prefers full sun in acidic, loamy or clay soils with regular moisture, and it’s appropriate for Zones 5 to 9.

While sourwood loves the sun, Leucothoe is all about the shade. Also known as doghobble, it is native to moist, acidic woods of eastern North America, with species L. fontanesiana and axillaris being the most available and bred for gardens. Resembling a midway point between Pieris and blueberry, these shrubs grow with zigzag branches of thick, shiny evergreen leaves, garnet and bronze when new, aging to deep green in summer and turning plum or red toward winter. Spring also brings Pieris-like springs of white flowers in tight clusters.

These colony-forming shrubs range two to six feet tall and as about as wide for cool moist, sandy, or loamy shade to part shade locations. Common cultivars include 'Greensprite', which can achieve five feet or more, with willowy foliage. ‘Nana’ and ‘Compacta’ are dwarf cultivars, while ‘Sarah’s Choice’ grows four feet around and offers heavier bloom and saturated red growth. Cultivars of L. fontanesiana include 'Zeblid' (also known as Scarletta); at a compact 18 to 24 inches tall and 3 to 4 feet wide, it can be used as a groundcover-like filler. It boasts pronounced maroon-red coloring. 'Rollisonii' is praised for its all-around vigor, while ‘Girard's Rainbow’, or simply ‘Rainbow’, has variegated leaves splashed with cream, pink, and plum and light green that require protection from burning. When comfortable it creates a stately fountain of a shrub. All leucothoe appreciate good air circulation to prevent foliage disease, plus protection from exposure to winter winds. They like cool moist, sandy or loamy shade to part-shade locations in Zones 5b to 8.

Zenobia is a small branch of North American native heaths found in the Southeast and Southern coastal regions alongside leucothoe. They share their name with a third-century queen of the Palmyrene Empire in Syria, and these shrubs are certainly royal. Of the three native species, Zenobia pulverulenta (dusty zenobia) is the most widely cultivated. Its selection 'Woodlander's Blue' is a wonderful addition to full sun or partial shade sites, growing two to five feet tall and roughly as wide. Semi-evergreen to deciduous, it has Vaccinium-like leaves that age to a unique, powdery gray-blue as the growing season progresses and turn brilliant yellow and red in the fall. It blooms in sweet, citrusy-scented racemes of oversize white flowers in late spring to early summer. It’s perfect for boggy, moist sites in acidic, well-drained soils, just like its azalea and blueberry cousins. Grow it in Zones 5 to 9.

The heath family stands nearly bar-none for acidic locations; its members deserve every bit of space tailored to their needs that you can offer. If approached with care, seldom will these gems let you down.

Image credit: steve-goacher/iStock/Getty Images