Cusick’s shadbush

Amelanchier alnifolia (Nuttall) Nuttall ex M. Roemer var. cusickii (Fernald) C. L. Hitchcock; A. basalticola Piper

Shrubs, 2–8 m. Stems 1–50, solitary or in colonies. Leaves fully unfolded; petiole (9–)12.8–19(–28) mm; blade elliptic to suborbiculate, (22–)33–46(–61) × (13–)25–32(–50) mm, base subcordate to truncate, each margin with (0 or)1–6(–11) teeth on proximal 1/2 and (2–)4 or 5(–7) teeth in distalmost cm, largest teeth 1 mm, apex usually truncate, sometimes mucronate to acute, abaxial surface glabrous or sparsely hairy by flowering, glabrous (or sparsely hairy) later, adaxial glabrous later. Inflorescences (4–)6–8(–10)-flowered, (17–)26–36(–47) mm. Pedicels: (0 or)1 or 2 subtended by a leaf, proximalmost (4–)9–14(–18) mm. Flowers: sepals erect to recurved after flowering, (2.6–)3.3–4.3(–5.3) mm; petals obovate to oblanceolate, (10.8–)13.3–20.1(–23.2) × (2.3–)3.3–6.3(–7.5) mm; stamens (14–)18–20(–21); styles (4 or)5, (1.7–)2.6–4(–4.8) mm; ovary apex glabrous or sparsely hairy (or with a ring of hairs at base of styles). Pomes bluish black, 10 mm diam. 2n = 4x.

Flowering Mar–Jul; fruiting May–Aug. Basaltic ledges, cliffs, and bluffs along streams, stony soil, streambeds, stream banks, copses, mountainsides, roadsides; 600–2300 m; B.C.; Idaho, Mont., Oreg., Wash.

Amelanchier cusickii has distinctively long petals. Leaves that are glabrous upon expanding and glabrous or sparsely hairy ovary apices are also useful for identification. The species flowers before A. alnifolia, which suggests that the two are genetically distinct. G. N. Jones (1946) noted that A. alnifolia and A. cusickii frequently grow together and that there is no evidence of hybridization; the authors have observed hybridization between A. alnifolia var. semiintegrifolia and A. cusickii.