Amelanchier humilis

Low shadbush, amélanchier bas

Description
Shrubs. Stems 1–50, commonly less than 1.5 m, occasionally to 8 m in shaded conditions, suckering and forming loosely scattered colonies: twigs glabrous at flowering. Leaves conduplicate in bud; partly or fully expanded and unfolded, green, abaxially densely white- or faintly yellow-tomentose (glabrate) by flowering; petioles 8–25 mm; blades abaxially pale green and slightly glaucous, elliptic or oblong to ovate or obovate, 2.5–5 x 2–4 cm, firm, bases rounded to cordate, margins serrate and often doubly serrate, nearly to or to base with 4–5(–6) teeth per cm or entire, lateral veins 7–13 pairs, remaining distinct near margins and not anastomosing , apices broadly subacute to rounded, mucronate, surfaces glabrous. Inflorescences 5–10-flowered, erect, 2–5 cm, only proximalmost 1–2 pedicels subtended by leaf. Pedicels hairy, proximalmost 0.8–1.5 cm. Flowers: hypanthia saucer-shaped, 3–5 mm diam.; sepals spreading to recurving after flowering , 2–5 mm, adaxially hairy; petals white to cream-colored, obovate-oblong, 7–10 x 4–5 mm, not andropetalous; stamens 20; styles 5; ovary summit rounded, densely lanuginose. Pomes almost black, 6–8 mm diam., sweet. 2n = 34, 68.

Flowering/Fruiting
Flowering Apr–May, fruiting Jul–Aug.

Habitat
Dry, open sites with rocky, gravelly, or sandy soil, often in calcareous regions; 0–5 00m

Range
Ont., Que.; Ill., Iowa, Md., Mich., Minn., Mo., N.Y., N.Dak., Ohio, Pa., S.Dak., Vt., Wis., W.Va.

Discussion
(see Systematics page for references cited)
Amelanchier humilis is distinctive for its strongly suckering habit, relatively coarsely toothed leaves with veins that usually remain distinct to the margin and do not anasomose, and preference for basic or neutral soils. A. humilis was considered to be conspecific with A. spicata by G. N. Jones (1946).

E. L. Nielsen’s (1939) three varieties (in addition to var. humilis) a ll grow in Minnesota, and A. humilis var. compacta was also reported from North Dakota and A. humilis var. campestris from South Dakota. The polymorphism of Amelanchier humilis in Minnesota is important in considering whether to recognize Nielsen’s A. mucronata. Amelanchier mucronata was originally based on collections from one bay on Lake Superior in one county in northeastern Minnesota. M. L. Fernald (1950) reported it from southeastern Manitoba. E. L. Nielsen (1939) stated that A. mucronata is most closely related to A. spicata (as A. stolonifera), and he pointed out distinctive differences in leaf shape and teeth and that A. mucronata is limited to basic rocks, whereas A. spicata is a calciphobe. Curiously, he did not comment on the potential relatedness of A. mucronata to A. humilis, which is strongly suckering , calciphilic, and common in Minnesota. A. mucronata leaves tend to be mostly entire, but A. humilis leaves can also be mostly entire. These two species both have an unusual color to the pubescence when young; emerging leaves are “yellow-green tomentose” in A. mucronata and faintly yellow- hairy in A. humilis (this species may also have white- hairy young foliage). They have similar saucer-shaped hypanthia, inflorescences, and flowers. Their morphologic similarity is implied by the fact that the only occurrence of A. mucronata in Nielsen’s key is in a couplet with A. humilis. In this couplet, A. mucronata is “Leaves mucronate, narrowly to broadly ovate; buds ellipsoid,” and A. humilis is “Leaves not mucronate, elliptic to oblong; buds ovate.” Nielsen’s description of A. mucronata, however, has the buds as “ovate-ellipsoid” and his description of A. humilis has the leaves “sometimes ovate.” We have examined at least one specimen (including types) from all nine collection numbers E. L. Nielsen (1939) listed for A. mucronata. Amelanchier mucronata does differ from A. humilis consistently in that its leaves are glabrate or nearly so by flowering, when leaves of A. humilis are mostly still quite hairy abaxially . This difference, in light of the many ways these two entities resemble one another, does not merit species status for A. mucronata.

M. L. Fernald (1950) reported hybrids between Amelanchier humilis and A. arborea, A. bartramiana, and A. spicata. We have observed putative hybrids with A. amabilis.

The description of Amelanchier erecta Blanchard is very close to A. humilis, but potential type material differs in the lengths of the petals and proximalmost pedicels. Further study is required before the affinities of A. erecta can be determined.