Rosa pisocarpa aka Cluster Rose

Rosa pisocarpa is a deciduous shrub in the rose family. Its common names include cluster rose and pea-fruited rose. It grows from southern British Columbia to northern California. Its range also reaches northern Idaho. It grows near streams and on shaded slopes. This rose can form thickets through its dense, branching growth. It suits woodland edges, wildlife gardens, and informal flower beds.

Garden plants reach about 1.6–3.3 feet [0.5–1 metre] tall and wide, according to RHS. Other accounts describe taller shrubs, reaching 7–8 feet [2.1–2.5 metres]. The bark is light brown. Young stems may be purple with a pale coating. Oregon State describes dark red or black stems. Sparse, straight prickles grow along the stems, sometimes in pairs. The leaves grow alternately and have a pinnate form. Each leaf has five to nine toothed leaflets. Fine hairs cover both sides of the green leaflets.

Small pink flowers grow in clusters of two to ten. Each flower has five petals around pale yellow stamens. The RHS describes one flowering period in midsummer. Rounded or egg-shaped hips follow the flowers. These turn red or orange-red and have a glossy surface. Each hip measures about half an inch across. Inside, a thin layer of flesh surrounds many seeds. The clustered fruit adds interest after the flowers fade. Leave stems unpruned after flowering to keep the hips.

Grow this rose in sun or partial shade. RHS recommends rich, moist soil that drains well. It accepts clay, loam, sand, and chalk across different pH levels. Oregon State also reports growth in waterlogged ground. RHS rates its UK hardiness as H5. PFAF lists USDA zones 5–9; Oregon State gives zone 7. Mulch in late winter or early spring. RHS recommends feeding in spring and early summer for flowering. Aphids, mites, scale insects, caterpillars, and sawflies may attack it. Deer and rabbits can also cause damage. Possible diseases include black spot, rust, powdery mildew, and dieback. Honey fungus and replant disease may also occur.

Sources differ on food use and safety. PFAF records hips eaten raw, cooked, or made into tea. It also lists seeds and peeled young shoots as foods. Hairs around the seeds can irritate the mouth and gut. RHS warns against eating the fruit, including for pets. PFAF records traditional medicinal uses of roots, bark, branches, and leaves. These records do not establish that such treatments work.