Quercus havardii |
Quercus arkansana |
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Havard oak, Havard's oak, Havard's shinnery oak, sand shinnery oak, sand shinoak, shinnery oak |
Arkansas oak |
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Habit | Shrubs, deciduous, low, forming clones 0.3-1.5 × 10 m, rhizomatous. | Trees, deciduous, to 15 m. Bark black with long rough ridges separated by deep furrows. |
Bark | light gray, scaly-papery. |
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Twigs | brown or grayish, 1-2.5 mm diam., glabrous or densely short grayish or yellowish tomentulose, glabrate in age. |
1.5-3 mm diam., gray-pubescent, rarely glabrate. |
Buds | dark red-brown, subglobose, ca. 2 mm, sparsely pubescent. |
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Leaves | blade green, often turning brownish with age, polymorphic, oblong or elliptic or sometimes lanceolate to oblanceolate or ovate to obovate, (30-)50-100 × (10-)20-50 mm, rather thick and hard, base rounded to cuneate, margins flat to revolute, at least some undulate, 2-3 rounded teeth on each side, secondary veins 5-8 on each side, much branched, apex broadly rounded, rarely acute; surfaces abaxially densely grayish or yellowish tomentulose or stellate-pubescent, sometimes only sparsely pubescent, secondary veins quite prominent, adaxially lustrous, very sparsely stellate-pubescent or glabrate, secondary veins very slightly if at all raised. |
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 | solitary or paired, subsessile or on peduncle to 10(-18) mm; cup from deeply cup-shaped to goblet-shaped, 10-12 mm deep × 15-25 mm wide, enclosing 1/3-1/2 nut, base rounded or slightly constricted, margin very thin and smooth, scales reddish brown, triangular-ovate to long-acute, proximally moderately to markedly tuberculate, pubescent, often canescent, tips loosely appressed; nut brown, ovoid, 12-25 × 14-18 mm. |
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. |
Cotyledons | distinct. |
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Terminal | buds red-brown, ovoid, 2-5 mm, glabrous or with scales somewhat ciliate on margins, especially at apex. |
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Quercus havardii |
Quercus arkansana |
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Phenology | Flowering spring. | Flowering spring. |
Habitat | Deep, shifting or stabilized sand dunes, off deep sands in putative hybrid populations | An understory tree of well-drained, sandy soils, on ravine heads (pocosins, steepheads) |
Elevation | 500-1500 m (1600-4900 ft) | 50-150 m (200-500 ft) |
Distribution |
NM; OK; TX
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AL; AR; FL; GA; LA; TX
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Discussion | Individual clones emerging to heights of 2-3 m from thickets occur sporadically across the Texas range of Quercus havardii and express some characteristics of Q. stellata, such as more deeply lobed leaves and smaller acorns. Such putative hybrids increase in frequency in the eastern part of the range of the species. Material of Quercus havardii from the Navajo Basin of Utah and adjacent Arizona has been treated as Q. havardii var. tuckeri Welsh. Welsh followed J. M. Tucker (1970) and interpreted these intermediate populations as putative hybrids between Q. havardii and both Q. turbinella and Q. gambelii. Giving varietal rank, instead of nothospecies status, to such populations seems arbitrary, and it certainly is inconsistent with their putative hybrid origins. (Discussion copyrighted by Flora of North America; reprinted with permission.) |
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. (Discussion copyrighted by Flora of North America; reprinted with permission.) |
Source | FNA vol. 3. | FNA vol. 3. |
Parent taxa | Fagaceae > Quercus > sect. Quercus | Fagaceae > Quercus > sect. Lobatae |
Sibling taxa | ||
Synonyms | Q. caput-rivuli | |
Name authority | Rydberg: Bull. New York Bot. Gard. 2: 213. (1901) | Sargent: Trees & Shrubs 2: 121. (1911) |
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