Prunus gracilis Engelm. & A. Gray, oklahoma plum. Shrub, deciduous, not spinescent, clonal forming low thicket, much–branched, in range shoots 30—90 cm tall; shoots with only cauline leaves in range initially with glandular teeth.
Stems ± cylindric, initially 1 mm diameter, densely short–tomentose (somewhat channeled beneath hairs); young twigs mostly < 3 mm diameter, with periderm having hairs, satiny purple–red bark; lower stem bark gray.
Leaves helically alternate, simple, petiolate, with stipules; stipules 2, flaplike wings attached to base of petiole with early–deciduous upper portion, ca. 4 mm long, initially whitish aging purplish red, upper portion lanceolate to narrowly triangular, to 3 mm long, with glandular teeth on margins, having some short hairs; petiole < 3—7 mm long; blade obovate to broadly elliptic, < 25—46 × < 13—24 mm tapered to broadly tapered at base often with 1—3 glands (extrafloral nectaries), the glands ca. 1 mm from petiole and 0.5 mm across, low–crenate on margins with a minute, spheroid, purple–red glandular point, acute to obtuse at tip, pinnately veined with principal veins sunken on upper surface and raised on lower surface, upper surface somewhat cobblestonelike, aging dull green with scattered hairs, lower surface conspicuously and densely short–tomentose and having glandular hairs hidden in tomentum and along principal and minor veins.
Inflorescence umbel–like clusters (fasciculate), axillary from 1—2(—3) buds per node (if 3, the central bud often narrower and vegetative), (1—)2—4–flowered per bud (to 7 flowers per node), bracteate; bud before opening ovoid, ca. 3 mm long, with purplish red, broadly ovate outer scales, short–ciliate on exposed margins, outer surface glabrous, inner surface often with appressed short hairs above midpoint, intermediate scales wedge–shaped whitish at base and mostly harder and orangish red, the inner scales fan–shaped to wedge–shaped, to 4.5 mm long, whitish and greenish with or without harder tissue at top, margins with conspicuous glandular teeth and appearing short–ciliate, outer (lower) surface ± glabrous, inner (upper) surface often short–hairy below midpoint; bractlets around bases of pedicels, oblong, 1—2.5 mm long, greenish, with conspicuous glandular teeth on margins above midpoint; pedicel at anthesis 3—4 mm long, green short soft–hairy.
Flower bisexual, radial, 10—13.5 mm across; bud slightly flattened on side touching adjacent flower; hypanthium bell–shaped, ± 2.5 × 1.3—1.7 mm, outer surface green and glabrate to pubescent, inner surface with nectary below filaments orangish (nectar not observed); sepals 5, arising from rim of hypanthium, initially erect later spreading, oblond to obtuse–ovate and cupped upward, 2—2.5 × 0.7—0.9 mm, green, margins with orangish glands on slender teeth, surfaces short–hairy; petals 5(—7), arising from rim of hypanthium, spreading, obovate, 3.5—6 × 2—3 mm, white, glabrous; stamens 25—30, free, arising from upper hypanthium and rim of hypanthium, radiating; filaments unequal, slender, 2.3—5.5 mm long, white, glabrous; anthers dorsifixed, dithecal, 0.6—0.7 mm long, light orangish yellow, with several short hairs, longitudinally dehiscent; pollen orangish yellow; pistil 1, 7.5—8 mm long; ovary superior, ellipsoid slightly compressed, ca. 1.5 × 1 mm, green, sparsely short–hairy, 1–chambered with 1 ovule; style in bud green aging whitish; stigma terminal, at level of many anthers, fleshy and spreading, aging orangish.
Fruit drupe, 1–stoned, ± spheroid, in range 15—16 × 16—19 mm, orange or red–orange to apricot or light scarlet, glabrous; endocarp (stone) lens–shaped, ca. 11 × 9.5 × 7 mm, with hairlike fibers on sides.
A. C. Gibson