Prunus nigra
Prunus mexicana
black plum, Canada plum, Canadian plum, prunier noir
bigtree plum, Mexican plum
with axillary end buds, usually glabrous, rarely hairy.
with axillary end buds, usually glabrous, sometimes hairy.
deciduous;
petiole 8–22 mm, glabrate with hairs adaxially, sometimes glandular distally, glands 1–3, discoid;
blade broadly elliptic to obovate, (5–)7–11 × 3–6.5 cm, base obtuse to rounded or subcordate, margins doubly crenate-serrate, teeth blunt, glandular, apex abruptly acuminate, abaxial surface hairy along midribs and major veins, adaxial glabrous.
deciduous;
petiole 4–18 mm, hairy, rarely only adaxially, usually glandular distally, glands 1–2(–4);
blade usually elliptic, sometimes broadly elliptic, obovate, ovate, or oblong, 6–12 × 3–7 cm, base usually obtuse to broadly rounded, sometimes subcordate, margins coarsely, doubly serrate, teeth sharp, eglandular, apex usually abruptly acuminate to acuminate, rarely acute, abaxial surface densely hairy, adaxial rugose, glabrous or hairy.
2–4-flowered, umbellate fascicles.
2–5-flowered, umbellate fascicles.
7–20 mm, usually glabrous, rarely hairy.
4–20 mm, usually glabrous, sometimes sparsely hairy.
blooming before or at leaf emergence;
hypanthium red-tinged, obconic, 3–4(–5) mm, usually glabrous, rarely hairy externally;
sepals broadly spreading to reflexed, ovate, 2–4(–5) mm, margins glandular-toothed, abaxial surface usually glabrous, rarely sparsely hairy, adaxial glabrous or hairy;
petals white, often fading to pink, suborbiculate to oblong-obovate, 8–13 mm;
ovaries glabrous.
blooming before leaf emergence;
hypanthium obconic, 2–4.5 mm, glabrous or hairy externally;
sepals reflexed, ovate to lanceolate, 1.5–4 mm, margins entire or irregularly or obscurely glandular-toothed, sometimes 2-fid at apices, ciliate, surfaces hairy;
petals white, sometimes turning pink, elliptic to obovate, 5–10 mm;
ovaries glabrous.
red, orange, or yellowish, barely glaucous, globose to ellipsoid, 15–30 mm, glabrous;
mesocarps fleshy;
stones ovoid-ellipsoid, strongly flattened.
purplish red to dark blue, glaucous, subglobose to ellipsoid, 15–30 mm, glabrous;
mesocarps fleshy;
stones ovoid-ellipsoid, strongly flattened.
= 16.
Prunus nigra
Prunus mexicana
In the northeastern United States and adjacent Canada, Prunus nigra co-occurs with, and is sometimes confused with, P. americana, despite being distinct in both flower and leaf. The red-tinged hypanthia and sepals of P. nigra give the entire inflorescence a pinkish coloration even when the petals are pure white, and the sepals bear obvious glandular teeth along their margins; in P. americana the hypanthia and sepals are green and the sepals bear relatively few glandular teeth or are eglandular. The leaf marginal teeth of P. nigra are rounded and bear glands at their tips or have callus scars where the glands fell off; those of P. americana are acute and eglandular; some may have a callused tip.
(Discussion copyrighted by Flora of North America; reprinted with permission.)
As L. H. Shinners (1956b) pointed out, plums from Texas determined as Prunus americana var. lanata Sudworth are not P. americana but P. mexicana. This was extrapolated by others to mean that all hairy americana-type plums, which had been called var. lanata, are P. mexicana. As a consequence, P. mexicana is often listed from states far from where it truly occurs (for example, North Carolina, Ohio, Wisconsin) and herbarium sheets of hairy P. americana can often be found filed under P. mexicana.
(Discussion copyrighted by Flora of North America; reprinted with permission.)
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