Prunus subcordata
Prunus americana
Klamath plum, Oregon plum, Pacific plum, Sierra or Klamath or Pacific plume, Sierra plum, western plum
American plum, prunier d'amérique, wild plum
with axillary end buds, glabrous or hairy.
with axillary end buds, usually hairy, sometimes glabrous.
deciduous;
petiole 4–18 mm, glabrous or hairy, usually glandular distally, glands 1–3, discoid;
blade elliptic, oblong-ovate, or suborbiculate, 2–5(–6.5) × 1.3–3.5(–4.5) cm, base rounded or subcordate, margins singly to doubly serrulate, teeth blunt, glandular, apex usually obtuse to rounded, rarely acute, abaxial surface glabrous or hairy, adaxial glabrous or appressed-hairy.
deciduous;
petiole 4–19 mm, usually hairy on adaxial surface, sometimes on both surfaces, rarely glabrous, usually eglandular, sometimes glandular distally, glands 1–2, discoid;
blade usually elliptic, broadly elliptic, or obovate, rarely ovate, 5–11 × 2–5.5 cm, base usually cuneate to obtuse, sometimes rounded, margins coarsely, doubly serrate, teeth sharp, eglandular, apex usually abruptly acuminate, rarely acute, surfaces glabrous or sparsely hairy along main veins.
2–5-flowered, umbellate fascicles.
2–5-flowered, umbellate fascicles.
5–15 mm, glabrous or hairy.
(4–)8–20 mm, usually glabrous, sometimes hairy.
blooming at leaf emergence;
hypanthium campanulate, 2–3.5 mm, glabrous or hairy externally;
sepals broadly spreading to reflexed, obovate, 2.2–4(–5) mm, margins glandular-toothed, sometimes obscurely so, sometimes ciliate, surfaces glabrous or hairy;
petals white, oblong-obovate, 5–10 mm;
ovaries usually glabrous, rarely hairy.
blooming before or at leaf emergence;
hypanthium obconic, 2.5–5 mm, usually glabrous, sometimes hairy, externally;
sepals broadly spreading to reflexed, ovate to lanceolate, 2–3.5(–5) mm, margins entire or irregularly or obscurely glandular-toothed, sometimes 2-fid at apices, ciliate, abaxial surface glabrous or hairy, adaxial tomentose;
petals white, oval to oblong-obovate, 7–12 mm;
ovaries glabrous.
usually red to reddish purple, sometimes yellow, globose to ellipsoid, 15–25 mm, usually glabrous, rarely puberulent;
mesocarps fleshy;
stones ovoid, ± flattened.
red, orange, or yellowish, glaucous, subglobose to ellipsoid, 15–30 mm, glabrous;
mesocarps fleshy;
stones ovoid, strongly flattened.
= 16.
Prunus subcordata
Prunus americana
Prunus subcordata shows variation in color, size, indument, and palatability of fruits, which has been the basis for recognition of taxonomic segregates. Variety kelloggii was described as a larger plant with less hairy foliage than in typical P. subcordata, and its fruits are yellow, larger, sweeter, and more pulpy. Variety rubicunda is a smaller shrub with bright red, bitter fruits. Most noteworthy is var. oregana with densely hairy ovaries and puberulent fruits, recorded only from the sparsely inhabited border region between northeastern California and adjacent Oregon. Specimens in herbaria are few and recent collections are lacking. The assignment of P. texana with hairy fruits to the plums (J. Shaw and R. L. Small 2005) makes this variant all the more interesting. Field study and collection followed by morphologic, genetic, and molecular study are needed to clarify its systematic position and significance.
(Discussion copyrighted by Flora of North America; reprinted with permission.)
Of our native plum species, Prunus americana is the most widely distributed and abundant in terms of individual plants. As might be expected, it is variable. U. P. Hedrick (1911) reported that about 260 horticultural varieties had been derived from it, far more than from any other North American plum. Not infrequently, individual specimens possess characteristics intermediate between P. americana and other plum species, probably the result of gene exchange, which seems to be common among American plums (J. Shaw and R. L. Small 2005).
The most obvious variation in Prunus americana is the presence or absence of indument on twigs, pedicels, hypanthia, sepals, petioles, and abaxial surfaces of leaves. The hairy form has been known by the epithets mollis and lanata, both as varieties of P. americana and at species rank. The type of P. mollis, upon which all of these names are ultimately based, is conspecific with that of P. nigra, and thus mollis and lanata are misapplied as infraspecific epithets of P. americana (L. H. Shinners 1956b). The hairy form is most abundant in the western part of the species range, where it is at least as prevalent as the glabrous form; hairy individuals are found throughout the range of the species. As in other species of Prunus, variation in indument is an easily noticed difference among individuals but not one of taxonomic significance.
In Missouri, Arkansas, and neighboring states, hairy Prunus americana intergrades with P. mexicana. In this zone of sympatry, they hybridize and produce intermediate forms, making determination of some herbarium specimens from this region difficult, if not arbitrary. One solution, not chosen here, would be to combine P. americana and P. mexicana into a single species. Tradition and morphologic distinctions argue for keeping them separate until more data can clarify the entire North American plum complex. Typically, P. americana is a shrub or tree to 80 dm tall and the plants sucker to form thickets; P. mexicana is a single tree 30–120 dm tall, rarely suckering. The leaves of P. americana are longer in proportion to their width than those of P. mexicana, and the leaf bases are cuneate in P. americana versus rounded or subcordate in P. mexicana. In hairy individuals of P. americana, the form most likely to be confused with P. mexicana, twigs are almost always hairy; about 70% of all P. mexicana specimens examined have glabrous twigs.
The following names have been misapplied to Prunus americana, though the types belong with that of P. nigra: Prunus americana var. lanata Sudworth, P. americana var. mollis (Torrey) Torrey & A. Gray, P. lanata (Sudworth) Mackenzie & Bush, and P. mollis Torrey.
(Discussion copyrighted by Flora of North America; reprinted with permission.)
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