Rubus allegheniensis is a prickly, arching shrub to 3 m tall; colonial; stems stout, prominently ridged, young stems finely glandular-hairy, sometimes glandular, thorns along main stems fairly straight, bases long, flattened side to side, canes upright to arching, green to dark red.
Leaves alternate, palmately compound, 5 leaflets, hairy below, terminal leaflet egg-shaped, about 15 cm long, widest at or below middle, margin toothed, thorns of leaf stalks and midribs hooked, leaf stalks glandular-hairy.
Flowers white, 2 cm wide in racemes on new growth branching off of primary stems of the last season, stems of inflorescence densely glandular–hairy, flowers insect pollinated; blooms May-June.
Fruit fleshy, of multiple 1-seeded black drupes (unripe fruit red) adhering to receptacle, shiny, June-Aug. Seed load 23% Pulp nutrients: water 89%, lipids <1%, protein 9%, CHO 49% (White 1989). Fruit eaten by numerous birds and mammals (Olmsted and Curtis 1947).
Wetland status: FACU-.
Frequency in NYC: Very common.
Habitat: Open areas, tolerates poor soil. Wetland hummocks and edges, to dry upland and fill. Typically mixed with Phragmites, herbaceous perennials (goldenrods) or greenbrier in burned over or otherwise disturbed areas. Wide tolerance of soils and moisture, grows in fill soils, pH 4.5-7.5. Moderately tolerant of flooding, drought, soil compaction, shade (grows poorly, does not flower in full shade). Intolerant of salt (Hightshoe 1988). Shaded out by closing forest canopy but may persist vegetatively. Stems and leaves eaten by rabbits and deer (Martin et al., 1951).
Notes: May provide sheltered sites for establishment of tree seedlings from competition by weedy herbs (Hanlon et al., 1998). May be infected by fireblight, a bacterial disease of rose family plants caused by Erwinia amylovora. This kills stems and leaves but often first appears in flowers, carried by insect pollinators. Infected parts become dark and shriveled, the infection travels progressively into flower stems and canes which die and turn brown or blackish. Wounded stems, especially those with frost damage, may be infected by Coral spot canker, Nectria cinnabarina (Ascomycotina). Fruiting bodies are of two types, those produced in mostly in spring are small, pinkish to purplish-red warty growths on dead bark or stems (turning black with age). Fruiting bodies produced in summer and fall are round, dark red-orange structures. Healthy plants can resist infection
(Sinclair et al. 1987).