Oaks of the World

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  Quercus turbinella

Greene 1889 Ill. W. Amer. Oaks 1: 37

Synonyms dumosa var. turbinella (Greene) Jepson 1895
dumosa subsp turbinella (Greene) E.Murray 1983
subturbinella Trel. 1924 (Camus = n 182) Diagnosis here
Local names shrub live oak ; turbinella oak ; Sonorian scrub oak ; California scrub oak ;
Range California; 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 !;

1.5-3.5 x 1-2 cm; evergreen; oblong or elliptic; 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;

Flowers March 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

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;
-- Sub-genus Quercus, Section Quercus, Series Leucomexicanae;
-- 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

-- subsp californica J.M.Tucker 1952
= Q. turbinella var. californica (J.M.Tucker) L.Benson
= Q.john-tuckeri Nixon & C.H.Muller 1994 Novon 4: 391
Tucker oak; desert scrub oak;
Section Quercus, subsection Dumosae

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 (but john-tuckeri has not stalked acorns) and
Q. berberidifolia (but john-tuckeri has leaves hairy above and pointed acorns); Q.cornelius-mulleri has leaves densely tomentose eneath, 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). Threatened (IUCN Red List Category : VU).
For Govaerts & Frodin it is a true species.