Quercus pumila |
Quercus robusta |
|
---|---|---|
runner oak, running oak |
robust oak |
|
Habit | Shrubs, deciduous or tardily deciduous, to 1 m. Bark gray to dark brown. | Trees, deciduous, to 13 m. Bark brown or black, roughly furrowed. |
Twigs | gray-brown to reddish brown, 1-2 mm diam., sparsely to uniformly pubescent. |
dark reddish brown, 1.5-2.5 mm diam., densely pubescent or glabrate. |
Leaves | blade oblong to narrowly obovate, 25-100 × 10-33 mm, base acute to rounded, margins entire, revolute, with 1 apical awn, apex acute or obtuse to rounded; surfaces abaxially uniformly gray-brown pubescent, rarely glabrate, adaxially somewhat convex, rugose, glabrous or with scattered hairs along midrib. |
blade acutely ovate to elliptic, widest at or proximal to middle, 55-120 × 20-50 mm, base cuneate to rounded or subcordate, margins with 6-8 teeth or shallow lobes with rounded sinuses, rarely entire, 1-10 awns, apex acute or attenuate; surfaces abaxially glabrous except for small axillary tufts of tomentum or pubescent along midrib, adaxially glabrous or persistently pubescent near base and along midrib. |
Acorns | annual; cup deeply saucer-shaped to turbinate, 5-12 mm high × 10-15 mm wide, covering 1/3-1/2(-2/3) nut, outer surface pubescent, inner surface densely pubescent, scales rarely involute, often tuberculate, tips tightly appressed, acute; nut globose to ovoid or broadly oblong, 9.5-15 × 9-12 mm, glabrate, scar diam. 5-8 mm. |
biennial; cup deeply cup-shaped, 6-9 mm high × 8-12 mm wide, covering 1/4-1/3 nut, outer surface puberulent or glabrate, inner surface uniformly pubescent, scales tightly appressed, acute or attenuate; nut oblong to broadly ellipsoid, 10-22 × 7-10 mm, glabrate, scar diam. 3.5-4.5 mm. |
Terminal | buds brown to red-brown, ovoid, 2.5-4.5 mm, glabrous or with ciliate scale margins. |
buds glossy light brown, acutely ovoid, 4-7 mm, glabrous or pubescent on apical 1/2. |
Quercus pumila |
Quercus robusta |
|
Phenology | Flowering spring. | Flowering spring. |
Habitat | Dry sandy soils of savannahs, low ridges and oak-pine scrub, occasionally at margins of poorly drained sites | Moist wooded canyons in Chisos Mountains |
Elevation | 0-100 m (0-300 ft) | 1500 m (4900 ft) |
Distribution |
AL; FL; GA; MS; NC; SC
|
TX |
Discussion | Although no hybrid combinations have been formally proposed, D. M. Hunt (1989) has reported evidence of hybridization with Quercus hemisphaerica, Q. incana, Q. myrtifolia, and Q. phellos. (Discussion copyrighted by Flora of North America; reprinted with permission.) |
Of conservation concern. After describing this species, C. H. Muller later (1951, 1970) concluded that it represented a hybrid between Quercus emoryi and Q. gravesii. The extreme forms (e.g., the type specimens) of Q. robusta and Q. gravesii are easily differentiated, but these two taxa appear to occupy the ends of a morphologic continuum. Muller's recent view, however, is that Q. robusta deserves species status. The origin of this taxon is still worthy of study. (Discussion copyrighted by Flora of North America; reprinted with permission.) |
Source | FNA vol. 3. | FNA vol. 3. |
Parent taxa | Fagaceae > Quercus > sect. Lobatae | Fagaceae > Quercus > sect. Lobatae |
Sibling taxa | ||
Name authority | Walter: Fl. Carol., 234. (1788) | C. H. Muller: Torreya 34: 119. (1934) |
Web links |