Prunus cerasifera
Prunus rivularis
cherry plum, myrobalan, myrobalan plum, purple leaf plum
creek plum, creek plume, hog plume
with axillary end buds, glabrous.
with axillary end buds, glabrous.
deciduous;
petiole 5–20 mm, glabrous except for a few hairs on adaxial surface, eglandular;
blade ovate, elliptic, or obovate, 3–7 × 1.5–3.5 cm, base obtuse, margins singly to doubly crenate-serrate, teeth blunt, glandular, apex obtuse to acute, abaxial surface hairy along midribs and veins, adaxial glabrous.
deciduous;
petiole 7–21 mm, glabrous or sparsely hairy on adaxial surface, glandular distally, glands 1–4;
blade lanceolate, oblong-lanceolate, or elliptic to narrowly elliptic, usually folded along midribs, 4–11 × 1.5–5 cm, base obtuse to rounded, margins singly to doubly crenate-serrulate, teeth blunt, glandular, glands inconspicuous, blackish, apex usually acuminate, sometimes acute, abaxial surface glabrous or ± hairy along midribs and veins, adaxial usually glabrous, rarely midribs hairy.
usually solitary flowers, sometimes 2-flowered fascicles.
2–4-flowered, umbellate fascicles.
(4–)10–18 mm, glabrous.
3–15 mm, glabrous.
blooming before leaf emergence;
hypanthium campanulate, 2–4 mm, glabrous externally;
sepals reflexed to spreading, oblong-ovate, 2–4 mm, margins glandular-toothed to nearly entire, eciliate, abaxial surface glabrous, adaxial hairy at bases;
petals white (reddish pink in cultivars), elliptic to suborbiculate, 7–14 mm;
ovaries glabrous.
blooming before or at leaf emergence;
hypanthium campanulate, 2–3 mm, usually glabrous, rarely glabrate, externally;
sepals broadly spreading to reflexed, oblong-ovate, 1.5–2.5 mm, margins glandular-toothed, abaxial surface glabrous or sparsely hairy, adaxial densely hairy at bases;
petals white, obovate, 4–7 mm;
ovaries glabrous.
purple-red to yellow, sometimes glaucous, ovoid, ellipsoid, or globose, 15–30 mm, glabrous;
mesocarps fleshy;
stones ellipsoid to ovoid, ± to strongly flattened.
usually red, sometimes yellowish orange, with white dots, not or only slightly glaucous, globose, 12–25 mm, glabrous;
mesocarps fleshy;
stones ovoid to subglobose, ± flattened.
= 16.
Prunus cerasifera
Prunus rivularis
The purple-leaved, pink-flowered cultivars of Prunus cerasifera are especially popular for ornamental use. The earliest purple form was introduced into European gardens about 1880 by M. Pissard, gardener to the Shah of Iran. Prunus cerasifera is widely used as a rootstock for commercial plums.
(Discussion copyrighted by Flora of North America; reprinted with permission.)
Prunus munsoniana is here placed in synonymy with P. rivularis, greatly expanding the range of the latter compared to its traditional treatment. Descriptions of P. munsoniana and P. rivularis differ mostly in size of the plants, leaves, and floral structures. As suggested by G. M. Diggs et al. (1999), P. munsoniana is simply a larger version of P. rivularis.
Evidence from analysis of DNA sequences of two nuclear genes in native plums (J. R. Rohrer et al. 2008) indicates that Prunus rivularis may be an allopolyploid. Three plants sequenced from Texas contained alleles seemingly derived from P. angustifolia on the one hand and P. hortulana (or P. murrayana) on the other. Further, two individuals determined as P. munsoniana, one each from Pennsylvania and Texas, had sequences very similar to those of P. rivularis.
Other specimens in herbaria labeled as Prunus munsoniana include hybrids between P. americana and P. angustifolia, as well as individuals of P. hortulana that bloom before the leaves emerge or that sucker freely.
(Discussion copyrighted by Flora of North America; reprinted with permission.)
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