Prunus nigra
Prunus myrtifolia
black plum, Canada plum, Canadian plum, prunier noir
West Indian cherry, West Indies or myrtle laurel cherry
with axillary end buds, usually glabrous, rarely hairy.
with terminal end buds, glabrous.
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.
persistent;
petiole 8–16 mm, glabrous, eglandular;
blade elliptic to broadly elliptic, 4–10 × 2–4.5(–6.5) cm, base cuneate, obtuse, or nearly rounded, margins undulate, entire, apex acute to acuminate, apicula obtuse, surfaces glabrous, abaxial glandular, glands 2, proximal, flat, circular to oval.
2–4-flowered, umbellate fascicles.
12–30-flowered, racemes;
central axes (11–)20–50 mm, leafless at bases.
7–20 mm, usually glabrous, rarely hairy.
(2–)3–6 mm, glabrous.
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.
usually bisexual, proximal sometimes staminate, blooming before leaf emergence;
hypanthium cupulate, 1.5–2.5 mm, glabrous externally;
sepals spreading, semicircular, 0.5–0.8 mm, margins usually entire, occassionally with a glandular tooth, surfaces glabrous;
petals white, obovate to suborbiculate, 1.5 mm;
ovaries glabrous.
red, orange, or yellowish, barely glaucous, globose to ellipsoid, 15–30 mm, glabrous;
mesocarps fleshy;
stones ovoid-ellipsoid, strongly flattened.
purple-black, globose to ± ovoid, 8–12 mm, glabrous;
mesocarps leathery;
stones subglobose, not flattened.
= 16.
Prunus nigra
Prunus myrtifolia
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.)
Prunus myrtifolia, when compared with P. caroliniana, has flowers more widely spaced on longer rachises and pedicels, and flowers in the winter rather than the spring. The leaves of P. myrtifolia are broader on average, and their apices are blunt at the tip; the fruits are more rounded at the apices with smaller apicula.
(Discussion copyrighted by Flora of North America; reprinted with permission.)
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