FNA: Quercus arizonica vs. Quercus douglasii

	Quercus arizonica	Quercus douglasii
	Arizona oak, Arizona white oak	blue oak
Habit	Trees, evergreen or subevergreen, small to moderate-sized trees, rarely to 18 m. Bark scaly.	Trees, deciduous, with single trunks, sometimes with few to several trunks.
Bark		gray, scaly.
Twigs	yellowish, 1.5-2.5 mm diam., persistently felty-tomentose, eventually dingy gray.	reddish or yellowish, ca. 2 mm, densely or sparsely puberulent, occasionally glabrate with age.
Buds	dull russet-brown, ovoid, distally subacute or rounded, 3 mm, sparsely pubescent or glabrate.	reddish brown, rarely yellowish, broadly ovoid to rarely subglobose, (2-)3-5 mm; scales glabrous except for ciliate margins, sometimes sparsely or densely pubescent.
Leaves	blade elliptic or oblong to narrowly obovate or oblanceolate, planar or moderately convex, to (30-)40-80(-90) × 15-30 mm, thick and leathery, usually stiff, base cordate or rounded and weakly cordate, margins entire or coarsely toothed especially near apex, cartilaginously revolute, teeth mucronate-tipped, obscure or prominent, secondary veins ca. 7-11 on each side, branching, passing into teeth when present, apex acute to usually obtuse or broadly rounded; surfaces abaxially dull, sparsely pubescent or subtomentose with curly branched hairs, reticulate from prominent, raised secondary veins, usually glaucous where exposed, adaxially dark or bluish green, moderately lustrous, sparsely and minutely stellate-pubescent, secondary veins slightly raised or prominent within depressions or impressed.	blade obovate or elliptic, oblong or oblanceolate, (20-)40-60(-80) × (15-)20-30(-40) mm, base rounded-attenuate or rounded, rarely cuneate, margins shallowly lobed or irregularly toothed, sometimes entire, lobes mucronate or rounded, secondary veins 6-10 on each side, apex rounded, rarely moderately acute; surfaces abaxially light green or blue-green, waxy, with scattered to crowded, semi-erect, (2-)4-6(-8)-rayed stellate hairs usually 0.2-0.6 mm diam. or larger, adaxially blue-green, glaucous or grayish, vestiture similar to abaxial surface.
Acorns	solitary or paired, subsessile, occasionally on peduncle to 15 mm; cup hemispheric or cup-shaped, 5-10(-15) mm deep × 10-15 mm wide, enclosing ca. 1/2 nut, base rounded, margin rather coarse, scales cream to brown, broadly ovate, evenly and strongly tuberculate, tomentose, tips closely appressed; nut light brown, ovoid or oblong, 8-12 mm, nearly glabrous.	subsessile, solitary; cup hemispheric or cup-shaped, rarely deeper, 5-10 mm deep × 10-15 mm wide, enclosing only base of nut, scales thin and not tuberculate to strongly and irregularly tuberculate, particularly toward base of cup; nut thin-walled, fusiform or subcylindric, 20-30 × 10-16 mm.
Cotyledons	connate.	distinct.
2n		= 24.

	Quercus arizonica	Quercus douglasii
Phenology	Flowering spring.	Flowering late winter–spring.
Habitat	Oak and pinyon woodlands, margins of chaparral, arroyos	Oak woodlands, margins of chaparral and grasslands
Elevation	1300-2500(-3000) m (4300-8200(-9800) ft)	0-1200 m (0-3900 ft)
Distribution	AZ; NM; TX; Mexico (Chihuahua, Coahuila, Durango, and Sonora) [WildflowerSearch map] [BONAP county map]	CA [WildflowerSearch map] [BONAP county map]
Discussion	Some of the specimens previously referred to Quercus endemica by C. H. Muller belong here instead. Putative hybrids between Quercus arizonica and Q. grisea (= Q. ×organensis Trelease) are problematic in local areas of contact from southeastern Arizona to western Texas. These intermediates tend to have narrower leaves than Q. arizonica, with moderately reticulate patterns of venation, and more densely hairy leaves. Quercus arizonica and Q. grisea are amply distinct elsewhere, including large areas in northern Mexico, and they appear to be more closely related to other species than to one another (e.g., Q. arizonica with Q. oblongifolia and Q. laeta Liebmann, and Q. grisea with Q. mohriana and Q. microphylla Née). Thus, Q. arizonica and Q. grisea are best treated as distinct species that hybridize, and not as conspecific populations. (Discussion copyrighted by Flora of North America; reprinted with permission.)	Populations of Quercus douglasii in coastal southern California and on the Channel Islands consist of small stands or solitary individuals often associated with Q. lobata and scrub oaks. Some doubt exists as to whether some or all of those populations are natural stands or are historical introductions near Native American settlements. Along the canyons of Santa Barbara County, putative hybrids between Q. douglasii and Q. dumosa are referred to Q. ×kinselae (C. H. Muller) Nixon. In the interior Coast Ranges of California are found numerous populations that are intermediate in form between Q. douglasii and Q. john-tuckeri (= Q. turbinella var. californica). This appears to be an area of secondary contact, and the two species remain distinct in nearby populations. Because of the widespread nature of the intermediates, following Tucker's extensive studies they can be conveniently referred to as the nothospecies Q. ×alvordiana Eastwood. The plants tend to be shrubs to small trees, with somewhat more spinose leaves than Q. douglasii and fruit similar to those of the latter species. (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. Quercus
Sibling taxa	Q. acerifolia, Q. agrifolia, Q. ajoensis, Q. alba, Q. arkansana, Q. austrina, Q. berberidifolia, Q. bicolor, Q. boyntonii, Q. buckleyi, Q. carmenensis, Q. chapmanii, Q. chihuahuensis, Q. chrysolepis, Q. coccinea, Q. cornelius-mulleri, Q. depressipes, Q. douglasii, Q. dumosa, Q. durata, Q. ellipsoidalis, Q. emoryi, Q. engelmannii, Q. falcata, Q. fusiformis, Q. gambelii, Q. garryana, Q. geminata, Q. georgiana, Q. graciliformis, Q. gravesii, Q. grisea, Q. havardii, Q. hemisphaerica, Q. hinckleyi, Q. hypoleucoides, Q. ilicifolia, Q. imbricaria, Q. incana, Q. inopina, Q. intricata, Q. john-tuckeri, Q. kelloggii, Q. laceyi, Q. laevis, Q. laurifolia, Q. lobata, Q. lyrata, Q. macrocarpa, Q. margarettae, Q. marilandica, Q. michauxii, Q. minima, Q. mohriana, Q. montana, Q. muehlenbergii, Q. myrtifolia, Q. nigra, Q. oblongifolia, Q. oglethorpensis, Q. pacifica, Q. pagoda, Q. palmeri, Q. palustris, Q. phellos, Q. polymorpha, Q. prinoides, Q. pumila, Q. pungens, Q. robur, Q. robusta, Q. rubra, Q. rugosa, Q. sadleriana, Q. shumardii, Q. similis, Q. sinuata, Q. stellata, Q. tardifolia, Q. texana, Q. tomentella, Q. toumeyi, Q. turbinella, Q. vacciniifolia, Q. vaseyana, Q. velutina, Q. viminea, Q. virginiana, Q. wislizenii	Q. acerifolia, Q. agrifolia, Q. ajoensis, Q. alba, Q. arizonica, Q. arkansana, Q. austrina, Q. berberidifolia, Q. bicolor, Q. boyntonii, Q. buckleyi, Q. carmenensis, Q. chapmanii, Q. chihuahuensis, Q. chrysolepis, Q. coccinea, Q. cornelius-mulleri, Q. depressipes, Q. dumosa, Q. durata, Q. ellipsoidalis, Q. emoryi, Q. engelmannii, Q. falcata, Q. fusiformis, Q. gambelii, Q. garryana, Q. geminata, Q. georgiana, Q. graciliformis, Q. gravesii, Q. grisea, Q. havardii, Q. hemisphaerica, Q. hinckleyi, Q. hypoleucoides, Q. ilicifolia, Q. imbricaria, Q. incana, Q. inopina, Q. intricata, Q. john-tuckeri, Q. kelloggii, Q. laceyi, Q. laevis, Q. laurifolia, Q. lobata, Q. lyrata, Q. macrocarpa, Q. margarettae, Q. marilandica, Q. michauxii, Q. minima, Q. mohriana, Q. montana, Q. muehlenbergii, Q. myrtifolia, Q. nigra, Q. oblongifolia, Q. oglethorpensis, Q. pacifica, Q. pagoda, Q. palmeri, Q. palustris, Q. phellos, Q. polymorpha, Q. prinoides, Q. pumila, Q. pungens, Q. robur, Q. robusta, Q. rubra, Q. rugosa, Q. sadleriana, Q. shumardii, Q. similis, Q. sinuata, Q. stellata, Q. tardifolia, Q. texana, Q. tomentella, Q. toumeyi, Q. turbinella, Q. vacciniifolia, Q. vaseyana, Q. velutina, Q. viminea, Q. virginiana, Q. wislizenii
Synonyms	Q. sacame	Q. douglasii var. ransomii, Q. ransomii
Name authority	Sargent: Gard. & Forest 8: 92. (1895)	Hooker & Arnott: Bot. Beechey Voy. 9: 391. (1840)
Web links	WildflowerSearch iNaturalist (observations) USDA Plants Database LBJ Wildflower Center SEINet Plants of the World Online Encyclopedia of Life Wikipedia Google Image Search	Local floras: CA Local Web sites: CalFlora, CalPhotos WildflowerSearch iNaturalist (observations) USDA Plants Database LBJ Wildflower Center SEINet Plants of the World Online Encyclopedia of Life Wikipedia Google Image Search

Quercus douglasii

Arizona oak, Arizona white oak

blue oak

Habit

Trees, evergreen or subevergreen, small to moderate-sized trees, rarely to 18 m. Bark scaly.

Trees, deciduous, with single trunks, sometimes with few to several trunks.

Bark

gray, scaly.

Twigs

yellowish, 1.5-2.5 mm diam., persistently felty-tomentose, eventually dingy gray.

reddish or yellowish, ca. 2 mm, densely or sparsely puberulent, occasionally glabrate with age.

Buds

dull russet-brown, ovoid, distally subacute or rounded, 3 mm, sparsely pubescent or glabrate.

reddish brown, rarely yellowish, broadly ovoid to rarely subglobose, (2-)3-5 mm;

scales glabrous except for ciliate margins, sometimes sparsely or densely pubescent.

Leaves

blade elliptic or oblong to narrowly obovate or oblanceolate, planar or moderately convex, to (30-)40-80(-90) × 15-30 mm, thick and leathery, usually stiff, base cordate or rounded and weakly cordate, margins entire or coarsely toothed especially near apex, cartilaginously revolute, teeth mucronate-tipped, obscure or prominent, secondary veins ca. 7-11 on each side, branching, passing into teeth when present, apex acute to usually obtuse or broadly rounded;

surfaces abaxially dull, sparsely pubescent or subtomentose with curly branched hairs, reticulate from prominent, raised secondary veins, usually glaucous where exposed, adaxially dark or bluish green, moderately lustrous, sparsely and minutely stellate-pubescent, secondary veins slightly raised or prominent within depressions or impressed.

blade obovate or elliptic, oblong or oblanceolate, (20-)40-60(-80) × (15-)20-30(-40) mm, base rounded-attenuate or rounded, rarely cuneate, margins shallowly lobed or irregularly toothed, sometimes entire, lobes mucronate or rounded, secondary veins 6-10 on each side, apex rounded, rarely moderately acute;

surfaces abaxially light green or blue-green, waxy, with scattered to crowded, semi-erect, (2-)4-6(-8)-rayed stellate hairs usually 0.2-0.6 mm diam. or larger, adaxially blue-green, glaucous or grayish, vestiture similar to abaxial surface.

Acorns

solitary or paired, subsessile, occasionally on peduncle to 15 mm;

cup hemispheric or cup-shaped, 5-10(-15) mm deep × 10-15 mm wide, enclosing ca. 1/2 nut, base rounded, margin rather coarse, scales cream to brown, broadly ovate, evenly and strongly tuberculate, tomentose, tips closely appressed;

nut light brown, ovoid or oblong, 8-12 mm, nearly glabrous.

subsessile, solitary;

cup hemispheric or cup-shaped, rarely deeper, 5-10 mm deep × 10-15 mm wide, enclosing only base of nut, scales thin and not tuberculate to strongly and irregularly tuberculate, particularly toward base of cup;

nut thin-walled, fusiform or subcylindric, 20-30 × 10-16 mm.

Cotyledons

connate.

distinct.

= 24.

Quercus arizonica

Quercus douglasii

Phenology

Flowering spring.

Flowering late winter–spring.

Habitat

Oak and pinyon woodlands, margins of chaparral, arroyos

Oak woodlands, margins of chaparral and grasslands

Elevation

1300-2500(-3000) m (4300-8200(-9800) ft)

0-1200 m (0-3900 ft)

Distribution

AZ; NM; TX; Mexico (Chihuahua, Coahuila, Durango, and Sonora)

[WildflowerSearch map]

[BONAP county map]

[WildflowerSearch map]

[BONAP county map]

Discussion

Some of the specimens previously referred to Quercus endemica by C. H. Muller belong here instead.

Putative hybrids between Quercus arizonica and Q. grisea (= Q. ×organensis Trelease) are problematic in local areas of contact from southeastern Arizona to western Texas. These intermediates tend to have narrower leaves than Q. arizonica, with moderately reticulate patterns of venation, and more densely hairy leaves. Quercus arizonica and Q. grisea are amply distinct elsewhere, including large areas in northern Mexico, and they appear to be more closely related to other species than to one another (e.g., Q. arizonica with Q. oblongifolia and Q. laeta Liebmann, and Q. grisea with Q. mohriana and Q. microphylla Née). Thus, Q. arizonica and Q. grisea are best treated as distinct species that hybridize, and not as conspecific populations.

(Discussion copyrighted by Flora of North America; reprinted with permission.)

Populations of Quercus douglasii in coastal southern California and on the Channel Islands consist of small stands or solitary individuals often associated with Q. lobata and scrub oaks. Some doubt exists as to whether some or all of those populations are natural stands or are historical introductions near Native American settlements. Along the canyons of Santa Barbara County, putative hybrids between Q. douglasii and Q. dumosa are referred to Q. ×kinselae (C. H. Muller) Nixon. In the interior Coast Ranges of California are found numerous populations that are intermediate in form between Q. douglasii and Q. john-tuckeri (= Q. turbinella var. californica). This appears to be an area of secondary contact, and the two species remain distinct in nearby populations. Because of the widespread nature of the intermediates, following Tucker's extensive studies they can be conveniently referred to as the nothospecies Q. ×alvordiana Eastwood. The plants tend to be shrubs to small trees, with somewhat more spinose leaves than Q. douglasii and fruit similar to those of the latter species.

(Discussion copyrighted by Flora of North America; reprinted with permission.)

Source

FNA vol. 3.

Parent taxa

Fagaceae > Quercus > sect. Quercus

Sibling taxa

Q. acerifolia, Q. agrifolia, Q. ajoensis, Q. alba, Q. arkansana, Q. austrina, Q. berberidifolia, Q. bicolor, Q. boyntonii, Q. buckleyi, Q. carmenensis, Q. chapmanii, Q. chihuahuensis, Q. chrysolepis, Q. coccinea, Q. cornelius-mulleri, Q. depressipes, Q. douglasii, Q. dumosa, Q. durata, Q. ellipsoidalis, Q. emoryi, Q. engelmannii, Q. falcata, Q. fusiformis, Q. gambelii, Q. garryana, Q. geminata, Q. georgiana, Q. graciliformis, Q. gravesii, Q. grisea, Q. havardii, Q. hemisphaerica, Q. hinckleyi, Q. hypoleucoides, Q. ilicifolia, Q. imbricaria, Q. incana, Q. inopina, Q. intricata, Q. john-tuckeri, Q. kelloggii, Q. laceyi, Q. laevis, Q. laurifolia, Q. lobata, Q. lyrata, Q. macrocarpa, Q. margarettae, Q. marilandica, Q. michauxii, Q. minima, Q. mohriana, Q. montana, Q. muehlenbergii, Q. myrtifolia, Q. nigra, Q. oblongifolia, Q. oglethorpensis, Q. pacifica, Q. pagoda, Q. palmeri, Q. palustris, Q. phellos, Q. polymorpha, Q. prinoides, Q. pumila, Q. pungens, Q. robur, Q. robusta, Q. rubra, Q. rugosa, Q. sadleriana, Q. shumardii, Q. similis, Q. sinuata, Q. stellata, Q. tardifolia, Q. texana, Q. tomentella, Q. toumeyi, Q. turbinella, Q. vacciniifolia, Q. vaseyana, Q. velutina, Q. viminea, Q. virginiana, Q. wislizenii

Q. acerifolia, Q. agrifolia, Q. ajoensis, Q. alba, Q. arizonica, Q. arkansana, Q. austrina, Q. berberidifolia, Q. bicolor, Q. boyntonii, Q. buckleyi, Q. carmenensis, Q. chapmanii, Q. chihuahuensis, Q. chrysolepis, Q. coccinea, Q. cornelius-mulleri, Q. depressipes, Q. dumosa, Q. durata, Q. ellipsoidalis, Q. emoryi, Q. engelmannii, Q. falcata, Q. fusiformis, Q. gambelii, Q. garryana, Q. geminata, Q. georgiana, Q. graciliformis, Q. gravesii, Q. grisea, Q. havardii, Q. hemisphaerica, Q. hinckleyi, Q. hypoleucoides, Q. ilicifolia, Q. imbricaria, Q. incana, Q. inopina, Q. intricata, Q. john-tuckeri, Q. kelloggii, Q. laceyi, Q. laevis, Q. laurifolia, Q. lobata, Q. lyrata, Q. macrocarpa, Q. margarettae, Q. marilandica, Q. michauxii, Q. minima, Q. mohriana, Q. montana, Q. muehlenbergii, Q. myrtifolia, Q. nigra, Q. oblongifolia, Q. oglethorpensis, Q. pacifica, Q. pagoda, Q. palmeri, Q. palustris, Q. phellos, Q. polymorpha, Q. prinoides, Q. pumila, Q. pungens, Q. robur, Q. robusta, Q. rubra, Q. rugosa, Q. sadleriana, Q. shumardii, Q. similis, Q. sinuata, Q. stellata, Q. tardifolia, Q. texana, Q. tomentella, Q. toumeyi, Q. turbinella, Q. vacciniifolia, Q. vaseyana, Q. velutina, Q. viminea, Q. virginiana, Q. wislizenii

Synonyms

Q. sacame

Q. douglasii var. ransomii, Q. ransomii

Name authority

Sargent: Gard. & Forest 8: 92. (1895)

Hooker & Arnott: Bot. Beechey Voy. 9: 391. (1840)

Web links

Unless otherwise noted, all data comes from the online version of the Flora of North America, who have made most of their content available via a Creative Commons license (CC BY 4.0).

Choose a data source: Flora of North America

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Quercus arizonica

Quercus douglasii

Quercus arizonica

Quercus douglasii