Amelanchier canadensis var. canadensis

Eastern shadbush, amélanchier du Canada

Description
Shrubs . Stems 1–25, 0.5–8 m, forming vaselike or alder-like clumps, fastigiate; twigs glabrous at flowering. Leaves conduplicate in bud; less than half-expanded and unfolded, green, abaxially densely tomentose by flowering; petioles 8–15 mm; blades abaxially green, oblong to oblong-elliptic or narrowly oblong-obovate, 1–5.5 x 1.8–2.8 cm, firm, bases rounded, margins serrate nearly to or to base with 6–11 teeth per cm (entire), lateral veins 10–15 pairs, anastomosing and becoming indistinct near margins , apices subacute to rounded, mucronate, surfaces glabrous. Inflorescences 4–10-flowered, erect, 4 –6 cm, only proximalmost 1–2 subtended by leaf. Pedicels hairy, proximalmost 1.4 –2 cm. Flowers: hypanthia campanulate, 3–5 mm diam.; sepals erect or loosely spreading after flowering , 1.5–3 mm, adaxially hairy; petals white, linear to oblong, 7.6–11 x 2–4 mm, not andropetalous; stamens 20; styles 5; ovary summit rounded, glabrous or occasionally sparsely hairy. Pomes maroon-purple, 7–10 mm diam., sweet. 2n = 34, 68.

Flowering/Fruiting
Flowering Mar–May, fruiting Jun–Jul.

Habitat
Mostly damp soils of swamps, wet streamheads, bogs, moist to wet thickets, woods; 0–200 m

Range
N.B., N.S., P.E.I., Que.; Conn., Del., D.C., Ga., Maine, Md., Mass., N.H., N.J., N.Y., N.C., Pa., R.I., S.C., Tenn., Vt., Va.

Discussion
(see Systematics page for references cited)
The vaselike or alder-like clumps of larger plants, erect inflorescences, usually glabrous ovary summit, and sepals that are erect or ascending after flowering are, in combination, distinctive for Amelanchier canadensis. Unusual features of A. canadensis its restriction mostly to the Atlantic coastal plain and t olerance of hydric soils; it is abundant in forested wetlands and ecotones with fresh-tidal marshes in the Chesapeake Bay region. K. M. Wiegand (1912) and C. T. Frye (2006) noted that the inflorescence of this species does not elongate much following flowering.

Amelanchier canadensis is remarkably plastic in habit, flowering at heights of less than 0.5 m in thin soils while growing up to 8 m in better conditions. New Brunswick and eastern Maine have a small variant of this species that does not appear to be edaphic. Amelanchier canadensis var. subintegra Fernald, which grows in low pine barrens of southeastern Virginia, was distinguished by having leaf blades that are entire or toothed only near the apex (M. L. Fernald 1950b). We are not recognizing this variety. Plants occurring at higher elevations in bogs, fens and other wetlands in the Appalachian Mountains have more rotund leaves with larger teeth and may warrant separate recognition.

Amelanchier canadensis is morphologically close to three species of eastern North America that have finely toothed leaves, glabrous ovary summits, and often grow into trees. These are A. arborea, A. intermedia, and A. laevis. Amelanchier canadensis is morphologically closest to A. intermedia. How these two species are distinguished is detailed in the discussion of the latter.

Amelanchier canadensis generally flowers at about the same time as A. laevis. M. L. Fernald (1950) and J. E. Cruise (1964) reported that A. canadensis hybridizes with A. arborea, A. intermedia, A. laevis, and A. spicata. C. T. Frye (2006) reported morphologic evidence of introgression with A. obovalis. A. canadensis was documented to be self-compatible and to produce seeds asexually (C. S. Campbell et al. 1987).