Practical ecological knowledge for the temperate reader.

Pacific Ninebark - Physocarpus capitatus

Family: Rosaceae - Rose family [E-flora]

Introduction: :The genus name Physocarpus, which is derived from the Greek for "bladder" (physa) and "fruit" (carpos), describes the plant's inflated seed pods or follicles. The species name capitatus refers to the flower head, which forms a dense, compact, round cluster. Ninebark's common name is based on the belief that its shredding bark has nine layers. The exfoliating bronzy bark, together with the shrub's arching form and affinity for stream banks, damp places, and woodlands, make P. capitatus easy to recognize." [PWNL]

Origin Status: Native [1.3]

Similar Species:
Dwarf Pacific Ninebark
"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."[E-flora]
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. [IFBC-E-flora]
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. [IFBC-E-flora]
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. [IFBC-E-flora]
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.[IFBC-E-flora]

Habitat & Range
Habitat: Moist to wet streamside thickets, forest edges, open forests, margins of lakes and marshes, clearings and roadsides in the lowland to montane zones.[IFBC-E-flora] Range: frequent in SW BC, locally frequent in SE BC; N to AK and S to N ID and CA. [IFBC-E-flora]

Ecological Indicator
"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." [IPBC-E-flora]


Edible Uses

Other Uses

Medicinal Uses


"A crude extract of Physocarpus capitatus aggregated actin in cells and induced the formation of binucleated cells, a sign of strong cytokinesis-inhibitory activity." [AAC]
"Bioassay-guided fractionation of Physocarpus capitatus yielded two new cucurbitacins (3 and 4) along with the known cucurbitacin F (1) and dihydrocucurbitacin F (2). Preliminary mechanism of action studies indicate that the cucurbitacins cause actin aggregates and inhibit cell division."[AAC]


Transplanting native plants from the wild has limited success.[PWNL]
"Pacific ninebark is hardy in the northern regions at low to middle elevations. It prefers a location which receives moisture year round such as a stream bank or the edge of a pond; but it will grow on drier sites once it is established. Ninebark is suited to either a shady or semi - shady site and will survive on the edge of an open area if mixed with other shrubs such as Indian plum (Oemleria cerasiformis), red osier dogwood (Cornus stolonifera), salmonberry (Rubus spectabilis), and cascara (Rhamnus purshiana). Use it as part of a hedge, or for a screening effect -- or perhaps against a backdrop of conifers." [PWNL]
"To propagate ninebark, take cuttings in the early spring or fall from either the newer reddish stems or the previous season's growth. The cutting should be approximately 15 to 20 centimetres in length, with the incision made at a point 0.5 centimetres below a leaf node (where the leaves join the stem). Remove any leaves that remain on the lower two - thirds of the twig and insert it into a damp mixture of equal parts sand and peat moss."[PWNL]
"Using 10 - centimetre plastic pots with drainage holes, place the cuttings around the edge of the pot about 2.5 centimetres apart. Firmly insert each twig so that it stands upright on its own. Remove any remaining leaves that are under the soil line, or any that eventually drop off (this will decrease the chance of fungal growth). Finally, label the pot with the plant name and the date as this will be helpful if you are taking other shrub cuttings -- or are starting cuttings at different times of the year."[PWNL]
"If you live on the west coast, you can place the pots outdoors in a sheltered spot. Otherwise, you should place them in a cold frame for the winter. Cuttings that are taken in the springtime can remain outside in a shady site, but they will need to be watered occasionally so don't forget about them entirely!"[PWNL]
The twigs should be rooted after approximately six weeks (or at the end of winter for fall cuttings). At that point, they can be transplanted into individual 10 - centimetre pots with drainage holes. Be sure to use a good compost mix, and to label each pot. Keep the newly potted up cuttings in a semi - shady location, such as under deciduous trees, until fall; and again, remember to water them."[PWNL]
"You can apply a weak, one - quarter strength fertilizer solution (20 - 20 - 20 or 15 - 30 - 15) to the cuttings every two weeks during the growing season if desired. In the fall, either transplant the cuttings into 15 - centimetre pots or into your garden location if the shrub appears large and strong enough. The shrub can be pruned back at planting time to increase bushiness. If ninebark is already on site, you can layer its lower branches in the spring to produce a transplantable shrub by the following spring. (Refer to methods of layering in general gardening books.)"[PWNL]
"The ripe seeds can also be collected from the follicles at the end of summer. Sow these on top of a good compost and sand mix in the fall or early spring. Use 10 - centimetre pots with drainageholes, and firmly press the soil mix into the pot leaving approximately one centimetre at the top. Cover the seeds with a thin layer of fine sand, such as cactus sand, and water them before labelling the pots and and placing them outdoors. Propagation by seeds will be somewhat slower than cuttings, but once the seeds have germinated, treat them as described above, transplanting as soon as the seedlings have two - to - four sets of leaves." [PWNL]

Use of Related Species

Physocarpus opulifolius - Common ninebark


Page last modified on Sunday, March 13, 2022 12:56 PM