Arkansas oak

Quercus caput-rivuli Ashe

Trees , deciduous, to 15 m. Bark black with long rough ridges separated by deep furrows. Twigs 1.5-3 mm diam., gray-pubescent, rarely glabrate. Terminal buds red-brown, ovoid, 2-5 mm, glabrous or with scales somewhat ciliate on margins, especially at apex. Leaves: petiole 5-25 mm, pubescent, rarely glabrate. Leaf blade rhombic to obovate or obtrullate, 50-150 × 35-100 mm, base acute to cordate, margins entire or with 2-3 shallow lobes and up to 10 awns, apex broadly obtuse to rounded; surfaces abaxially uniformly pubescent to glabrous except for conspicuous axillary tufts of tomentum, veins prominent, adaxially planar or somewhat rugose with a few persistent hairs near base. Acorns biennial; cup thin, shallow goblet- to almost saucer-shaped, 5-9 mm high × 10-16 mm wide, covering 1/4-1/2 nut, outer surface puberulent, inner surface sparsely to uniformly pubescent, scale tips appressed, acute; nut broadly ellipsoid to subglobose, 10-15 × 9-15 mm, puberulent, scar diam. 5-10 mm.

Flowering spring. An understory tree of well-drained, sandy soils, on ravine heads (pocosins, steepheads); 50-150 m; Ala., Ark., Fla., Ga., La., Tex.

Quercus arkansana reportedly hybridizes with Q . incana (= Q . × venulosa Ashe) and Q . nigra (D. M. Hunt 1986; W. H. Duncan and M. B. Duncan 1988). While agreeing that an isotype of the former clearly indicated a relationship to Q . arkansana , E. J. Palmer (1948) questioned the identity of the second parent and noted that venulosa is a homonym of a fossil species. In addition, D. M. Hunt (1989) cited evidence of hybridization with Q . hemisphaerica , Q . laevis , Q . marilandica , Q . myrtifolia , and either Q . falcata or Q . velutina .