7. Prunus mexicana S. Watson (big tree plum, wild plum)
Pl. 536 a, b;
Map 2477
Plants trees to
12 m tall, usually not suckering or colonial. Branches sparsely thorny. Twigs
usually glabrous, but occasionally hairy, producing pseudoterminal winter buds
(these usually in a cluster of 2 or 3 at the tip). Petioles 4–18 mm long,
usually evenly hairy on all sides, usually with 1 or 2(–4) large, dark,
club-shaped glands near the tip. Leaf blades 6–12 cm long, 3–7 cm wide, 2 times
as long as wide or wider, obovate to oblong-ovate, less commonly elliptic,
broadly elliptic, or ovate, broadly angled to more commonly rounded or
shallowly cordate at the base, short-tapered or tapered to rarely angled to a
sharply pointed tip, the margins coarsely and doubly toothed, the sharp teeth
relatively straight, glandless, the upper surface glabrous to moderately
short-hairy and appearing somewhat wrinkled, the undersurface densely
short-hairy. Inflorescences produced before the leaves, umbellate clusters of
2–5 flowers per bud, the flower stalks 4–20 mm long, glabrous or sparsely
hairy. Flowers with the hypanthium 2.0–4.5 mm long, conic, usually glabrous,
rarely finely hairy. Sepals 1.5–4.0 mm long, reflexed at flowering, lanceolate
to ovate, rounded or sometimes minutely notched or toothed at the tip, the
margins hairy, entire or obscurely glandular, the inner surface moderately to
densely hairy. Petals 6–12 mm long, elliptic to obovate, white, sometimes
fading to pink. Fruits 15–30 mm long, ellipsoid to nearly globose, shallowly longitudinally
grooved on 1 side, the surface purplish red to dark blue, glabrous, glaucous,
the fleshy layer well-developed, the stone ovoid-ellipsoid, somewhat flattened,
the surface usually smooth. 2n=16. April–May.
Scattered to
common nearly throughout the state (South Dakota to Texas east to Indiana and
Georgia; Mexico). Banks of streams and rivers, mesic upland forests, margins of
ponds, bases and tops of bluffs, edges of glades, and edges of sand prairies;
also pastures, old fields, fencerows, old mines, railroads, and roadsides.
Prunus
mexicana is sometimes
planted as an ornamental or as a wildlife food plant. Specimens attributed to
this species sometimes are morphologically intermediate with P. americana
and P. hortulana. For a discussion of putative hybridization in this
complex see the treatments of those species.