Physocarpus opulifolius — Ninebark
Physocarpus is commonly called ninebark for the exfoliating layers of bark that slowly peel away on older branches. Over time, reddish to light brown inner layers are exposed, most noticeable in winter after leaf drop. In spring, burgundy new stems at branch tips extend beyond dense foliage.
Native along streams in western U.S. mountainous regions, Physocarpus capitatus adapts easily to more arid sites. A somewhat twiggy multi-stemmed shrub, it grows 5-12 ft. in height and width. Rounded pinkish white spring blossoms 1-2 in. wide are similar to those on spirea, which is also in the large Rosaceae family along with Physocarpus. Fall foliage turns red-orange before leaf drop.
Ninebark may be planted as a specimen, hedge, screen, or part of a mixed border. It is generally not particular about soil and can grow happily with low or moderate water. It prefers a semi-shaded situation in the hottest inland valleys but can take full sun and little summer water closer to the coast. Pruning is needed only to control wayward branches; frequent pruning is discouraged and may initiate an awkward form. To rejuvenate plants, cut all stems close to the ground.
Physocarpus opulifolius is native to eastern and central North America but many of its selections are popular in western states. All thrive with low to moderate summer irrigation and good drainage in winter. Leaves somewhat resemble lobed maples or grape leaves but are much smaller, 2-3 in. long. Several named cultivars offer foliage in dark green, purple, copper, maroon, golden yellow, or lime and are most dynamic when planted in sharp contrast with plant partners.
‘Coppertina’ has copper leaves in spring that deepen in hue before turning dark red in fall. With moderate growth, it eventually reaches 8-12 ft. high and wide as arching branches reach out all around. Pinkish white flower clusters create a striking scene.
‘Diablo’ boasts reddish purple or reddish brown foliage on a shrub nearly as wide as its 8-10 ft. height; foliage tends to develop more of a deep green cast in shaded sites. ‘Luteus’ has a similar size but a completely different look with yellow foliage in sun, yellowish green in shade.
Gardens that cannot accommodate large shrubs may have space for one of the more compact cultivars, although they, too, reach considerable size. ‘Dart’s Gold’ matures to about 5 ft. tall and as wide. Emerging leaves in spring are an eye-catching, golden-yellow hue. Later in summer, the foliage ages to a quieter lime-green, and in autumn, its greenery shifts back to yellow with an overlay of bronzy-red. After cream-colored blossom clusters fade, bright red berries appear until they desiccate several weeks later. ‘Nanus’ grows 2-4 ft. with small, dark green leaves.
‘Summer Wine,’ a fairly new hybrid of Physocarpus ‘Nana’ and Physocarpus ‘Diablo’ features darkly colored crimson-red foliage with the same flowers and fall color as ‘Diablo.’ It matures at about 5-6 ft. in height and width.