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alder-leaf shadbush, amélanchier à feuilles d'aulne, saskatoon, saskatoon berry, saskatoon serviceberry, service berry, western serviceberry

Cusick's serviceberry, Cusick's shadbush, saskatoon

Habit Shrubs, 1–12 m. Stems 1–50, solitary or colonial. Shrubs, 2–8 m. Stems 1–50, solitary or in colonies.
Leaves

mostly unfolded;

petiole (3–)6.8–19.1(–28) mm;

blade usually elliptic to oval to suborbiculate, sometimes quadrangular, (14–)24–47(–67) × (7–)17–36(–55) mm, base usually subcordate to truncate, sometimes ± tapering or ± cuneate, each margin with 0–3(–9) teeth on proximal 1/2 and (0–)3–5(–8) teeth in distalmost cm, largest teeth more than 1 mm, apex rounded to truncate or occasionally acute or mucronate, abaxial surface sparsely to densely hairy (or glabrous) by flowering, sparsely to moderately hairy (or glabrous) later, adaxial glabrous or sparsely (moderately) hairy later.

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–)6–11(–16)-flowered, (8–)14–43(–62) mm.

(4–)6–8(–10)-flowered, (17–)26–36(–47) mm.

Pedicels

(0 or)1 or 2(or 3) subtended by a leaf, proximalmost (2–)3–20(–29) mm.

(0 or)1 or 2 subtended by a leaf, proximalmost (4–)9–14(–18) mm.

Flowers

sepals erect to recurved after flowering, (1.4–)2.2–4(–4.9) mm;

petals oblanceolate to oval or obovate to elliptic, (5.7–)9.5–14(–18.8) × (2.2–)3.3–5.2(–6.6) mm;

stamens (10–)15–21(–22);

styles (3 or)4 or 5(or 6), (1.3–)2–2.9(–3.9) mm;

ovary apex moderately to densely hairy (or glabrous).

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

black or purple, 8–15 mm diam.

bluish black, 10 mm diam. 2n = 4x.

Amelanchier alnifolia

Amelanchier cusickii

Phenology Flowering Mar–Jul; fruiting May–Aug.
Habitat Basaltic ledges, cliffs, and bluffs along streams, stony soil, streambeds, stream banks, copses, mountainsides, roadsides
Elevation 600–2300 m (2000–7500 ft)
Distribution
from FNA
AK; AZ; CA; CO; IA; ID; KS; MN; MT; ND; NE; NM; NV; OR; SD; TX; UT; WA; WY; AB; BC; MB; NT; ON; SK; YT
[WildflowerSearch map]
[BONAP county map]
from FNA
ID; MT; OR; WA; BC
[WildflowerSearch map]
[BONAP county map]
Discussion

Varieties 3 (3 in the flora).

Amelanchier alnifolia is widespread and polymorphic, and its taxonomic and geographic limits have been viewed differently. L. Cinq-Mars (1971) considered this species to range eastward to the Gaspé Peninsula. Disagreements about the boundary between A. alnifolia and A. humilis are evident in herbarium specimen annotations. The distinctness of the varieties of A. alnifolia has also been questioned. G. N. Jones (1946) treated the three varieties recognized here as distinct species and noted that the leaves of var. alnifolia and var. semiintegrifolia (A. florida) are virtually indistinguishable, and, although petal lengths of the two do not overlap, occasional larger-flowered var. alnifolia and occasional smaller-flowered var. semiintegrifolia occur, so the petal length distinction is not an absolute one. Geographically these two varieties are largely separate, with var. alnifolia occurring in the Great Plains and Rocky Mountains and var. semiintegrifolia on the Pacific slopes of mountains from Alaska to northern California.

Amelanchier alnifolia is thought to hybridize with Sorbus scopulina (x\Amelasorbus jackii Rehder).

(Discussion copyrighted by Flora of North America; reprinted with permission.)

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.

(Discussion copyrighted by Flora of North America; reprinted with permission.)

Key
1. Ovary apices glabrous (or sparsely hairy); shrubs 1–2(–4) m.
var. pumila
1. Ovary apices moderately to densely hairy (or glabrous); shrubs or trees, 1–12 m
→ 2
2. Inflorescences (8–)26–43(–62) mm; proximalmost pedicels (5–)8–16(–29) mm.
var. alnifolia
2. Inflorescences (8–)14–26(–35) mm; proximalmost pedicels (2 or)3–8(–13) mm.
var. semiintegrifolia
Source FNA vol. 9, p. 651. FNA vol. 9, p. 652.
Parent taxa Rosaceae > subfam. Amygdaloideae > tribe Maleae > Amelanchier Rosaceae > subfam. Amygdaloideae > tribe Maleae > Amelanchier
Sibling taxa
A. amabilis, A. arborea, A. bartramiana, A. canadensis, A. cusickii, A. fernaldii, A. gaspensis, A. humilis, A. interior, A. intermedia, A. laevis, A. nantucketensis, A. nitens, A. pallida, A. sanguinea, A. spicata, A. utahensis
A. alnifolia, A. amabilis, A. arborea, A. bartramiana, A. canadensis, A. fernaldii, A. gaspensis, A. humilis, A. interior, A. intermedia, A. laevis, A. nantucketensis, A. nitens, A. pallida, A. sanguinea, A. spicata, A. utahensis
Subordinate taxa
A. alnifolia var. alnifolia, A. alnifolia var. pumila, A. alnifolia var. semiintegrifolia
Synonyms Aronia alnifolia A. alnifolia var. cusickii, A. basalticola
Name authority (Nuttall) Nuttall ex M. Roemer: Fam. Nat. Syn. Monogr. 3: 147. (1847) Fernald: Erythea 7: 121. (1899)
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