Prunus spinosa
Prunus nigra
blackthorn, blackthorn plum, sloe, sloe cherry
black plum, Canada plum, Canadian plum, prunier noir
with axillary end buds, hairy.
with axillary end buds, usually glabrous, rarely hairy.
deciduous;
petiole 4–7 mm, hairy, eglandular;
blade elliptic to obovate, 1.5–4 × 1–2.2 cm, base obtuse to rounded, margins crenulate-serrulate, teeth blunt, often glandular, apex acute to obtuse, abaxial surface hairy (especially along midribs and veins), adaxial glabrate.
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.
usually solitary flowers, sometimes 2-flowered fascicles.
2–4-flowered, umbellate fascicles.
0.5–5(–8) mm, usually glabrous, rarely hairy.
7–20 mm, usually glabrous, rarely hairy.
blooming before leaf emergence;
hypanthium cupulate, 1.5–2.5 mm, glabrous externally;
sepals spreading, oblong, 1.5–2.5 mm, margins glandular-toothed, surfaces glabrous or adaxially hairy at bases;
petals white, elliptic, 4–8 mm;
ovaries 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.
bluish black, globose, 10–15 mm, glabrous;
mesocarps fleshy;
stones subglobose, ± flattened.
red, orange, or yellowish, barely glaucous, globose to ellipsoid, 15–30 mm, glabrous;
mesocarps fleshy;
stones ovoid-ellipsoid, strongly flattened.
= 32.
= 16.
Prunus spinosa
Prunus nigra
As past flora writers (C. L. Hitchcock et al. 1955–1969; E. G. Voss 1972–1996) have noted, the distinctions between Prunus spinosa and P. domestica are not clear. Some researchers consider the hexaploid P. domestica to have been derived from the tetraploid P. spinosa, often in a scenario involving hybridization with P. cerasifera. It should not be surprising that some of the characters used in keys to separate these three taxa (spininess, indument, leaf size, pedicel length, numbers of flowers per bud) are subject to variation within each species and overlap among the species.
(Discussion copyrighted by Flora of North America; reprinted with permission.)
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.)
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BC, 
OR, 
WA - Local Web sites:
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