36. Prunus mexicana S. Watson, Proc. Amer. Acad. Arts. 17: 353. 1882.
Mexican or bigtree plum
Trees, rarely suckering, 30–120 dm, sparsely thorny. Twigs with axillary end buds, usually glabrous, sometimes hairy. Leaves deciduous; petiole 4–18 mm, hairy, rarely only adaxially, usually glandular distally, glands 1–2(–4); blade usually elliptic, sometimes broadly elliptic, obovate, ovate, or oblong, 6–12 × 3–7 cm, base usually obtuse to broadly rounded, sometimes subcordate, margins ˂coarsely˃, doubly serrate, teeth sharp, eglandular, apex usually abruptly acuminate to acuminate, rarely acute, abaxial surface densely hairy, adaxial ˂rugose˃, glabrous or hairy. Inflorescences 2–5-flowered, umbellate fascicles. Pedicels 4–20 mm, usually glabrous, sometimes sparsely hairy. Flowers blooming before leaf emergence; hypanthium obconic, 2–4.5 mm, glabrous or hairy externally; sepals reflexed, ovate to lanceolate, 1.5–4 mm, margins entire or irregularly or obscurely glandular-toothed, sometimes 2-fid at apices, ˂ciliate˃, surfaces hairy; petals white, sometimes turning pink, elliptic to obovate, 5–10 mm; ovaries glabrous. Drupes purplish red to dark blue, ˂glaucous˃, subglobose to ellipsoid, 15–30 mm, glabrous; mesocarps fleshy; stones ovoid-ellipsoid, strongly flattened.
Flowering Mar–Apr; fruiting Aug–Oct. Stream bottoms, open woods, edges of woods; 10–400 m; Ala., Ark., Ill., Ind., Iowa, Kans., Ky., La., Miss., Mo., Okla., Tenn., Tex.; Mexico (Coahuila, Nuevo León, San Luis Potosí, Tamaulipas).
As L. H. Shinners (1956b) pointed out, plums from Texas determined as Prunus americana var. lanata Sudworth are not P. americana but P. mexicana. This was extrapolated by others to mean that all hairy americana-type plums, which had been called var. lanata, are P. mexicana. As a consequence, P. mexicana is often listed from states far from where it truly occurs (for example, North Carolina, Ohio, Wisconsin) and herbarium sheets of hairy P. americana can often be found filed under P. mexicana.