Prunus mexicana S. Watson, Mexican plum, big–tree plum, wild plum. Small tree, winter–deciduous, with 1 trunk, in range to 6 m tall; shoots with only cauline leaves, young foliage short–hairy and somewhat velveteen.

Stems

Stems cylindric with persistent leaf bases, glabrous; bark on typical individuals gray with horizontally oriented lenticels, on trunk of large individual orange–brown with vertical fissures.

Leaves

Leaves helically alternate, simple, petiolate, with stipules; stipules 2, attached on leaf base just beneath petiole, narrowly elliptic to linear or narrowly lanceolate, 4—6 mm long, dissected and shallowly serrate, somewhat winged at base and sometimes with 1—several lobes, short–ciliate and often with short teeth having amber glandular tips on margins, short–hairy, early–deciduous; petiole channeled, 2—12 mm long, densely short–hairy; blade broadly elliptic or ovate to elliptic–obovate, 25—100 × 11—57 mm, broadly tapered to subtruncate or truncate and somewhat oblique at base (never cordate), serrate on margins with 4—5 nonglandular, acute teeth/10 mm and sparsely short–ciliate, acute at tip, pinnately veined with principal veins sunken on upper surface and raised on lower surface, short–villous and somewhat velveteen, sometimes with 1—2 green, torch–shaped or club–shaped glands at base or upper petiole.

Inflorescence

Inflorescence umbel–like cyme, in range 2—4 flowers/cluster on short, lateral spur shoot, bracteate; spur shoot axis to 2 mm long, scales of spur shoot lanceolate, flat, pubescent on inner surface; bracts subtending pedicel 2, ovate, 4—6 mm long, to 2.5 mm wide decreasing upward, translucent with several, fine brown–red parallel veins, having a broad, straight base; bractlet subtending pedicel linear to oblanceolate–linear, < bract, with several glandular teeth on margins and fringed approaching tip, upper surface short–hairy above midpoint; pedicel at anthesis 9—12 mm long increasing in fruit, glabrous

Flower

Flower radial, bisexual, 12—19 mm across; hypanthium bell–shaped, 3.5—4 × 3 mm, green blushed reddish and puberulent on outer surface, whitish around rim, inner surface with light orange, gland–dotted, nectar–producing thickening, nectar forming as small beads of nectar; sepals 5, in flower spreading (somewhat reflexed after flowering), obtuse–triangular to obovate or somewhat rounded and somewhat cupped, 2.8—3.3 × 1.5—2 mm, green with reddish–orange glandular teeth above midpoint, wavy on margins, venation inconspicuous; petals 5, clawed, arising from rim of hypanthium, spreading; claw < 1 mm long, dark rose, limb broadly elliptic to roundish with narrow base, 5.5—9.3 × 4—6.3 mm, white or reddish like claw at base, pinnately veined, near base with several short hairs on both surfaces; stamens ± 30 in several series, 5 stamens/sepal and 1 stamen/petal, free, arising from rim of hypanthium; filaments 4.6—6.9 mm long, white or bases occasionally reddish, glabrous; anthers dorsifixed, dithecal, 0.8—1 mm long, pale light yellow, longitudinally dehiscent with the longest stamens dehiscing last; pollen light yellow; pistil 1, 12.5—13 mm long; ovary superior, ellipsoid, ca. 1 × 0.6 mm, light green, 1–chambered with 1 ovule; style ca. 0.35 mm diameter, light green, glabrous; stigma terminal, disclike, 0.7 mm across.

Fruit

Fruit drupe, in umbel–like cluster to 4 fruits, spheric, 14—17 × 15—16 mm, grayish tinged purplish and conspicuously glaucous; mesocarp ca. 4 mm thick, yellowish; endocarp (stone) like that of cherry, 12—14 × 11—12 × 6.5—7 mm, yellowish, without surface fibers; pedicel straight, < 20 mm long, < 1 mm diameter at midpoint, on spur shoot above numerous bud scars.

A. C. Gibson