Mountain shadbush, amélanchier de Bartram
Shrubs. Stems 1–50, 0.3–2.5(–5) m, suckering and forming +/- dense clumps, fastigiate; twigs glabrous at flowering. Leaves imbricate in bud; half-expanded, brownish or green, and glabrous by flowering; petioles 2–10(–15) mm; blades abaxially green, elliptic-oval to elliptic-oblong, 2–6 x 1.5–3.5 cm, membranous or firm, bases usually cuneate, margins serrate, sometimes doubly, nearly to base, with 6–12 teeth per cm, lateral veins 10–16 pairs, anastomosing and becoming indistinct near margins and not entering teeth, apices acute to rounded, surfaces glabrous. Inflorescences 1–3(–4)-flowered, erect, 2–4 cm, all but terminal pedicel subtended by leaf. Pedicels glabrous, proximalmost 1–3 cm. Flowers: hypanthia campanulate, 3–6 mm diam.; sepals ascending to recurving after flowering , 3–5 mm, hairy adaxially; petals white, oblong-oval, 6–12 x 3–5 mm, not andropetalous; stamens 20; styles (4–)5; ovary summits conic, densely lanuginose. Pomes dark purple, 1–1.5 cm diam., insipid. 2n = 34, 68.
Flowering May–Aug,; fruiting Jul–Sep.
Cool woods, mountain slopes, summits, bogs, poor fens, conifer swamps, acidic soils, sandy lake shores, stream banks, rocky ridges, roadside thickets; 0–15 00m
St. Pierre and Miquelon; N.B., Nfld. & Labr., N.S., Ont., P.E.I., Que.; Maine, Mass., Mich., Minn., N.H., N.Y., Pa., Vt., W.Va.
(see Systematics page for references cited)
No other North American Amelanchier has leaves that are imbricate in bud, fewer than four flowers per inflorescence, and petioles usually less than 1 cm. Because of these differences, P. Landry (1975) placed A. bartramiana in its own subgenus, with all other members of the genus worldwide in another. W. H. Blanchard (1907), W. A. Robinson and C. R. Partanen (1980), and W. A. Robinson (1982) also recognized the distinctness of this species. Amelanchier bartramiana grows farther north than any other species of the genus in eastern North America, and more than other shadbushes, it occupies relatively undisturbed habitats, such as peatlands and natural breaks in mature forests. Finally, it is the only species that has been documented to produce seed sexually (C. S. Campbell et al. 1987; there may well be other exclusively or predominantly sexual taxa in the genus, which have not been well sampled in this regard. Sexual plants of A. bartramiana are self-incompatible diploids. A. C. Dibble et al. (1998) reported a tetraploid individual, which had very large petals and might have been autotetraploid.
Plants in some populations of Amelanchier bartramiana in eastern Canada are small in many vegetative and reproductive parts but otherwise identical to this widespread species.
Amelanchier bartramiana generally flowers with A. laevis, and it frequently hybridizes with other members of the genus. M. L. Fernald (1950) and L. Cinq-Mars (1971) reported hybrids with A. arborea (A. x\quinti-martii Lalonde), A. canadensis, A. fernaldii, A. gaspensis, A. humilis, A. intermedia, A. laevis, A. sanguinea, A. spicata, and A. interior. The hybrid with A. laevis, A. x\neglecta Eggleston, can usually be found when these two species grow together (J. E. Weber and C. S. Campbell 1989).