Prunus pensylvanica
Prunus spinosa
bird cherry, cerisier de pennsylvanie, fire cherry, petit merisier, pin cherry, pin or bird or fire cherry
blackthorn, blackthorn plum, sloe, sloe cherry
with terminal end buds, glabrous.
with axillary end buds, hairy.
deciduous;
petiole (7–)9–20 mm, glabrous, glandular distally, glands 1–3;
blade elliptic, oblong-lanceolate, or lanceolate, (2.5–)4.5–10(–14) × 1.5–5 cm, base cuneate to rounded, margins crenulate to crenate-serrate, teeth blunt, glandular, apex usually acuminate, sometimes acute (western specimens), surfaces glabrous.
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.
2–5(–8)-flowered, umbellate fascicles or corymbs;
central axes 0–8(–24) mm.
usually solitary flowers, sometimes 2-flowered fascicles.
(8–)10–30 mm (subtended by minute bracts), glabrous.
0.5–5(–8) mm, usually glabrous, rarely hairy.
blooming at leaf emergence;
hypanthium obconic, 1.8–3 mm, glabrous externally;
sepals reflexed, oblong, 1.2–2.8 mm, margins entire, surfaces glabrous;
petals white, elliptic, obovate, or suborbiculate, 4–7 mm;
ovaries glabrous.
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.
bright red, ellipsoid, 6–10 mm, glabrous;
mesocarps fleshy;
stones ellipsoid, not flattened.
bluish black, globose, 10–15 mm, glabrous;
mesocarps fleshy;
stones subglobose, ± flattened.
= 16.
= 32.
Prunus pensylvanica
Prunus spinosa
Throughout most of its range, Prunus pensylvanica appears distinct from P. emarginata. The leaves of P. pensylvanica are generally larger and lanceolate to ovate-lanceolate rather than oblanceolate to elliptic; the leaf apices are usually acuminate (sometimes acute) versus rounded to obtuse (rarely acute) in P. emarginata. Inflorescences of P. pensylvanica are corymbose to umbellate with central axes shorter than pedicels; in P. emarginata the inflorescences are corymbose to racemose with central axes longer than pedicels. Where their ranges overlap in British Columbia and western Montana, intermediates are found with the corymbose inflorescence of P. emarginata and leaves more comfortably accommodated within the variation of P. pensylvanica. Some of these specimens have been identified as P. corymbulosa, based on a type from Montana, here included within P. pensylvanica.
Along the eastern slopes of the Rockies and throughout the northwestern Great Plains, Prunus pensylvanica is shrubby and has smaller leaves (less than 60 mm) than it does farther east. Compared to leaves of eastern plants, those of western specimens are also broader in proportion to their length (1.7–2.3:1 versus 2–4.3:1), have acute rather than acuminate apices, and tend to be more coarsely toothed. Although sometimes segregated as var. saximontana, or subsp. corymbulosa, when having a corymbose inflorescence, these plants fit within the variation in plant habit, leaf size, leaf shape, and margin serration seen throughout the broad range of P. pensylvanica.
(Discussion copyrighted by Flora of North America; reprinted with permission.)
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.)
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