Oaks of the World

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 Quercus turbinella
AuthorGreene 1889
Synonymsdumosa var. turbinella (Greene) Jepson 1895
dumosa subsp turbinella (Greene) E.Murray 1983
subturbinella Trel. 1924 (Camus = n 182)
Local namesshrub live oak ; turbinella oak ; Sonorian scrub oak ; California scrub oak ;
RangeCalifornia; New-Mexico; Arizona; Colorado; North of Mexico; 600-2500 m;
Growth habit reaches 4 metres tall; but most often bushy, tortuous; numerous underground runners, extending to 500 m around the main root !;
Leaves

1.5-3.5 x 1-2 cm; evergreen; oblong or elliptical; thick, stiff, leathery; apex pointed or acuminate; base rounded or slightly cordate; margin somewhat wavy, sometimes entire, more often with 3-8 pairs of sharp, 2 mm mucronate teeth; hairless, blue green above; yellow green beneath with tufts of flattened glandular and 7-13 rayed stellate, spreading hairs; 4 to 7 vein pairs conspicuous beneath; petiole 1-4 mm long, reddish or yellowish, hairy;

FlowersMarch to June; male flowers with 4-7 stamens;
Fruits acorn 1.5-2.3 m; oblong, narrow; apex pointed; pale brown; peduncle 1-4 cm long; cup scaly, shallow, enclosing 1/4 to 1/3 of nut; maturing in 1 year in July to September;

Bark, twigs and
buds

bark pale grey, rough, fissured; young twigs hairy, smooth, red brown; older twigs dark grey, hairless; buds brown, globose, pubescent, 1-2 mm long;
Hardiness zone, habitat hardy zone 7 (withstands -15C); all types of soils; prefers dry slopes in mountains;
Miscellaneous -- A. Camus : 176;
-- "white oak" (= section Quercus );
-- hybrids with
Q.gambelii, Q.douglasii, Q.lobata and with Q.grisea which it resembles (to distinguish them, see the stellate hairs beneath the leaves, that have spreading rays in Q.turbinella, and are fascicled in Q.grisea); resembles too Q.john-tuckeri that has subsessile, blackish acorns, and base of leaves not cordate; resembles too Q.palmeri but the latter has larger leaves, and cup much broader than acorn; Q.cornelius-mulleri has leaves dull yellow green above, and are densely tomentose beneath;
Subspecies and
varieties

-- subsp californica J.M.Tucker 1952
= Q. turbinella var. californica (J.M.Tucker) L.Benson
= Q.john-tuckeri Nixon & C.H.Muller 1994
Tucker oak; desert scrub oak;
evergreen shrub 1-3(5) metres tall; twigs tomentose; buds globose 2 mm in diameter; leaves concolorous 1-3.5 x 1-2 cm, leathery, apex pointed or rounded; base cuneate or rounded; margin irregularly toothed, spiny, greyish green above with stellate hairs, pale green, bloomy beneath with dense stellate hairs; acorn solitary, subsessile, spindle-like, 2-3 cm long, pointed, dark brown; cup shallow, thin, with warty scales; 900-2000 m, en dry sites; California; resembles Q turbinella (that has not stalked acorns) and
Q. berberidifolia that has leaves hairy above and pointed acorns); Q.cornelius-mulleri has leaves densely tomentose beneath, looking like bicolor;

-- var. ajoensis (C.H.Muller) Little 1979
= Q.ajoensis C.H.Muller 1954   (A. Camus : 182)
= Q. turbinella subsp ajoensis (C.H.Muller) Felger & Lowe
Ajo mountain scrub oak ;
evergreen shrub 2-3 m tall, sometimes more; spreading branches; twig hairless; bark scaly, thin, grey; small buds brown, globose, sometimes tomentose, 1-1.5 mm long; leaves 1.5-3.5 x 1-2 cm, leathery; apex acute, mucronate; base cordate or rounded, asymmetrical; margin flat, cartilaginous, with 6-8 pairs of spiny teeth; hairless and glaucous above; yellow green, almost glabrous, bloomy beneath, with prominent midrib; 3-8 vein pairs, slightly curved; petiole 3-5 mm long, densely pubescent, dark; acorn oblong 1.2-1.5 cm long, with a slender peduncle 3-5 mm long, cup shallow, thin, brown; 500-2000 m; Arizona (Ajo Mountains), Mexico (Baja California).
For Govaerts & Frodin it is a true species.

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