Shrubs or trees, ?sometimes fastigiate?, 2–250 dm; ?suckering and/or rhizomatous, sometimes forming colonies?. Stems 1–150, erect to ascending; bark usually gray, sometimes brown or salmon colored, ?smooth or fissuring in older trees?; short shoots present or absent; unarmed; young stems glabrous or hairy. Leaves deciduous, cauline, simple; stipules caducous, free, linear, margins entire; petiole present; blade elliptic, elliptic-oblong, elliptic-oval, ovate, oval, oblanceolate, oblong, oblong-ovate, obovate, quadrangular, suborbiculate, or orbiculate, 0.2–10 × 0.2–6 cm, membranous to coriaceous, ?base tapering or truncate to rounded or cordate?, margins flat, entire or serrate, sometimes doubly serrate, or dentate distally or throughout, venation pinnate, ?apex acuminate to truncate or retuse, or mucronate to apiculate?, abaxial surface glabrous or sparsely to densely hairy by flowering, glabrous or ± hairy at maturity, ?usually paler than adaxial surface?. Inflorescences terminal, ?arching, ascending, erect, or drooping, sometimes spreading or nodding?, 1–4-flowered clusters or 4–17-flowered racemes (panicles); bracts absent; bracteoles sometimes present. Pedicels present, ?proximal 1–3 subtended by leaves?. Flowers opening during leaf expansion, perianth and androecium epigynous, 10–55 mm diam.; hypanthium campanulate or funnelform to saucer-shaped, 3–9 mm diam., hairy or glabrous; sepals 5, erect to reflexed, triangular to lanceolate; petals 5, usually white, sometimes ivory, rarely ± pink, linear to orbiculate; stamens 7–28, shorter than or equal to petals; carpels 2–5, connate, adnate to hypanthium, ?ovary 6–10-loculed by false partitions?, apex densely hairy or glabrous, styles ?2–6?, terminal, distinct or ± connate; ovules 2. Fruits pomes, bluish or purplish to nearly black, pinkish or maroon-purple, dark purple-blue, or brownish, globose (pear-shaped in A. bartramiana), 6–15 mm diam.; ?taste insipid to sweet?; hypanthium persistent; sepals persistent, erect to strongly reflexed; carpels cartilaginous; styles sometimes persistent. Seeds absent or few. x = 17.
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Hypanthium obconic, campanulate, or saucer-shaped; sep 5, erect to reflexed, persistent; pet 5, white; stamens usually 20, shorter than the pet; ovary inferior, 5-locular in our spp., the 5 styles distinct or partly connate; ovules 2 per locule, soon separated by a partition growing in from the back of each carpel, the 10-seeded pome therefore apparently 10-locular; unarmed shrubs or trees with simple, alternate, serrate lvs and medium-sized fls in rather short, often leafy-bracteate racemes (rarely reduced to a single fl) terminating the branches of the season and opening with or before the lvs; x=17. 20, N. Temp.Genus beset with hybridization, polyploidy, and apomixis (as shown by the frequent apparently fertile triploids). Plants called A. intermedia Spach probably reflect hybridization between A. canadensis and A. arborea or A. laevis. Plants called A. interior Nielsen, found mainly in Minn., Wis., e. Io., and n. Mich., may be a hybrid swarm or a set of segregating polyploids derived from A. laevis and A. sanguinea. Plants called A. wiegandii Nielsen may reflect hybridization between A. sanguinea and A. arborea or A. laevis. Plants called A. nantucketensis E. P. Bicknell may be hybrids between A. canadensis and A. spicata. Other hybrids also occur and may be to some degree self-perpetuating.
Shrubs or trees, deciduous; buds conspicuous, narrowly conical, with several scales. Leaves simple, petiolate, stipulate, venation camptodromous, margin entire or serrate. Racemes terminal; bracts caducous. Hypanthium campanulate. Sepals 5, margin entire. Petals 5, white, oblong or lanceolate, slender. Stamens 10–20. Ovary inferior or semi-inferior, 2–5-loculed, with 2 ovules per locule, separated by a false partition from back of locule; styles 2–5, partly connate or free. Fruit a small berrylike pome, bluish black to dark purple, usually juicy and sweet, incompletely 4–10-loculed, with one seed in each locule, crowned by persistent, usually recurved sepals.
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