Physocarpus opulifolius aka Nine Bark

Physocarpus opulifolius, or ninebark, is a shrub in the rose family. It comes from central and eastern North America, including eastern Canada. Wild plants grow beside streams, on rocky slopes, and in moist thickets. The shrub sheds its leaves each fall. Several stems form a dense clump with upright, arching branches. Garden plants often reach 5–10 feet (1.5–3 metres) tall and wide. The RHS gives a taller upper limit of 13 feet (4 metres).

The bark gives ninebark its name and much of its interest. Older branches shed long strips, exposing brown and reddish inner layers. Winter leaf loss makes these layers easier to see. Dense, tangled twigs can still hide much of the bark. Young twigs are thin and reddish brown, with tight bark. The green leaves grow in an alternate pattern along the stems. Each simple leaf has three to five lobes and toothed edges. Fall brings muted yellow, bronze, or copper tones rather than bright color.

Small white or pink flowers form rounded clusters along the branches. Each flower has five petals and many stamens. Most sources place bloom in late spring or early summer. Reported dates range from April through July, depending on the source. Flowers develop on older growth and draw bees. Birds and butterflies also visit the shrub. Reddish, swollen seed pods follow the flowers in hanging groups. These fruits appear in summer and ripen into fall.

Ninebark grows in full sun or partial shade. Some shade helps at the southern edge of its range. It prefers soil that drains well but accepts many soil types. Clay, sand, loam, and rocky ground can all support it. It tolerates acid and alkaline soils, though shallow chalk may cause yellow leaves. Established plants withstand drought, heat, and compacted soil. Sources place it in USDA zones 2–8; the RHS rates it H7. It needs little care and transplants with ease.

Use ninebark in hedges, screens, shrub borders, or native gardens. Groups of plants can help hold soil on worn slopes. Prune after bloom when thinning or shortening branches is needed. Winter cutting can renew an old shrub. Pests cause few problems, but diseases can affect it. These include powdery mildew, fireblight, leaf spots, and honey fungus. No edible uses are known. Historical bark remedies exist, but large medicinal doses can be toxic.