Physocarpus (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, becoming most noticeable in winter after leaf drop. In spring, burgundy new stems at branch tips erupt with dense foliage.

Large Deciduous Shrubs

Two ninebark species are widely grown in Sonoma County:  Physocarpus opulifolius is native to eastern and central U.S.; Physocarpus capitatus is native along streams in mountainous regions of California and western North America. Both are easily grown in Sonoma County.

• Both species adapt to somewhat arid microclimates but require ample moisture for 1-2 years as their roots become established. Moderate summer irrigation is needed thereafter, less in partial shade, more in inland sites.
• Rounded, pinkish white spring blossoms attract pollinators to the 2-5 in. wide clusters similar to those on Spiraea (spirea). Both shrubs are in the large Rosaceae Shiny red seed capsules form in fall.
• Growth is fairly rapid as shrubs reach 6-8 ft. tall and wider.
• Pruning is needed only to control wayward branches; frequent pruning is discouraged and may initiate an awkward form.
• Older branches can be removed at ground level or close to interior stems when they develop leafless twigs.
• To completely rejuvenate plants, cut all stems close to the ground.

Garden Placement

Ninebark may be planted as a specimen, hedge, screen, or part of a mixed border. 

• This multi-stemmed shrub can become twiggy on interior branches. When planted in full view, appearance is enhanced with judicious thinning.
• Place ninebark where it has plenty space to spread while reaching mature size. Arching branches are best looking when not crowding neighboring plants.
• Ninebark is generally not particular about soil and can grow happily with low or moderate water, in mild microclimates or in partial shade. 
• It prefers a semi-shaded situation with regular summer moisture in the hottest inland valleys but can take full sun and little summer water closer to the coast.

Colorful Foliage

The various species and cultivars each offer their own colorful attractiveness with foliage resembling that of small Japanese maples. Several have spring and summer leaves in dark green, purple, copper, maroon, golden yellow, or lime. All are most dynamic when planted in sharp contrast with flattering garden partners. In fall, foliage turns red-orange. Selection may depend on a particular garden location.

• ‘Coppertina’ has coppery-colored leaves in spring before turning dark red in fall. Pinkish white flower clusters create a striking scene 8-10 ft. high and wide.
• ‘Diablo’ boasts reddish purple or dark 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.
  • ‘Summer Wine,’ is a 5-8 ft. shrub with dark foliage.
  • ‘Nanus’ is a hybrid of ‘Diablo’ and ‘Summer Wine’ and is said to mature at about 4-5 ft. in height and width or a little larger.
  • ‘Dart’s Gold’  has eye-catching, golden-yellow leaves in spring that age in summer to a quieter lime-green before returning to golden yellow in autumn with an overlay of bronzy-red. Mature size may be larger than a projected 5 ft. height and width.

September 2023