General: Medium to tall shrub, 1-4 m tall; branches erect to arching, angled, smooth to minutely star-shaped-hairy when young, eventually with brown, shredding bark.
Leaves: Alternate, deciduous, the stalks 1-3 cm long, the blades egg- to heart-shaped in outline, 3-10 cm long, palmately 3- or 5-lobed, the lobes irregularly double-toothed, deeply veined, shiny dark green above, paler and with abundant star-shaped hairs below.
Flowers: Inflorescences dense, terminal, half-rounded clusters of numerous stalked flowers, the stalks woolly; corollas white, saucer-shaped, the petals 5, nearly circular, 3-5 mm long; calyces densely star-shaped-hairy, 5-lobed, the lanceolate lobes about 3 mm long, somewhat bent back; ovaries superior; stamens about 30, pink.
Fruits: Follicles, 3 to 5, barely joined at the base, inflated, 7-11 mm long, reddish, mostly smooth; seeds 1 to 4 per follicle, pear-shaped, yellowish, hardened, shiny.
Moist to wet streamside thickets, forest edges, open forests, margins of lakes and marshes, clearings and roadsides in the lowland to montane zones; frequent in SW BC, locally frequent in SE BC; N to AK and S to N ID and CA.
Pacific ninebark is a large shrub frequently reaching four meters in height, but the dwarf mutant grows to be only about one-half meter in height, with horizontal spreading branches. Such dwarf mutants may involve a mutation affecting the normal growth hormones in the plant, or they could affect some biosynthetic pathway that is necessary for normal growth. Despite its small size, the mutant produces normal leaves and flowers.
Source: Extracted from Griffiths and Ganders, 1983, Wildflower Genetics: A Field Guide for British Columbia and the Northwest.
Ecology
Ecological Framework for Physocarpus capitatus
The table below shows the species-specific information calculated from original data (BEC database) provided by the BC Ministry of Forests and Range. (Updated August, 2013)
A shade-tolerant/intolerant, Western North American dciduous shrub distributed more in the Pacific than the Cordilleran region. Occurs in wet cool temperate and cool mesothermal climates on very moist to wet, nitrogen-rich soils (Moder and Mull humus forms); its occurrence decreases with increasing elevation and continentality. Scattered in semiopen or open-canopy forests on water-receiving and watercollecting sites, typically on fine-textured, gleyed alluvial soils with fluctuating groundwater table. Usually associated with Cornus sericea and Rubus spectabilis. Characteristic of alluvial floodplain forests.
Griffiths, Anthony J. F. and Fred R. Ganders. 1983. Wildflower Genetics: A Field Guide for British Columbia and the Pacific Northwest. Flight Press, Vancouver.
