Physocarpus capitatus aka Pacific Ninebark

Physocarpus capitatus is known as Pacific or western ninebark. This deciduous shrub belongs to the rose family, Rosaceae. Its native range runs from Alaska into the western United States. Oregon State describes its range from British Columbia to central California. It also reaches east into western Montana and grows in Oregon. It lives in temperate regions, often near fresh water. Stream banks, lake shores, wet ground, and moist woods provide habitat.

This shrub has an open shape with loose, angled branches. Oregon State gives a height of 5–20 feet [1.5–6 metres]. Its width is less than its height. Virginia Tech describes an upright shrub reaching 12 feet [3.7 metres]. These accounts show that its final size can vary. Thin bark adds interest beyond the leaf and flower seasons. It ranges from yellow-brown to orange-brown on older stems. As stems age, their bark splits and sheds long strips. Young, slender twigs start with tight, orange-brown bark.

The leaves grow in an alternate pattern along the stems. Each leaf is simple, with three to five pointed lobes. The outline looks much like a small maple leaf. Veins spread from the leaf base toward the lobes. The edges have a double row of teeth. Upper surfaces are dark green and may look slightly glossy. Lower surfaces are paler and bear fine hairs. The shrub loses its leaves at the end of the growing season.

Small white flowers form rounded clusters at the branch tips. The clusters stand upright and have a domed top. Bloom falls in late spring and can reach early summer. Each flower has five petals and many stamens. Flowers contain both male and female parts. Small, swollen fruits follow, held together in dense clusters. These fruits are follicles, which change from reddish tones to brown. Their clustered form remains a useful feature for plant identification.

In gardens, Pacific ninebark accepts both sun and shade. Oregon State reports that it does best in acid soil. It needs some watering, which fits its moist native habitats. The same source rates it hardy to USDA Zone 5. Cuttings offer an easy way to raise new plants. Its peeling bark, lobed leaves, and white flowers offer seasonal interest.