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Quercus douglasii
BLUE OAK

Higher Taxonomy
Family: FagaceaeView DescriptionDichotomous Key

Common Name: OAK FAMILY
Habit: Shrub, tree, evergreen or not; monoecious. Leaf: simple, alternate, petioled; margin entire to lobed; stipules small, generally deciduous. Staminate Inflorescence: catkin or stiff spike, many-flowered. Pistillate Inflorescence: 1--few-flowered, generally above staminate inflorescence; involucre bracts many, generally overlapping, flat or cylindric. Staminate Flower: calyx generally 4--6-lobed, minute; petals 0; stamens 4--12+. Pistillate Flower: calyx generally 6-lobed, minute; petals 0; ovary inferior, style branches generally 3. Fruit: 1 nut subtended, partly enclosed by scaly, cup-like involucre or 1--3 nuts subtended, enclosed by spiny, bur-like involucre; mature years 1--2. Seed: generally 1.
Genera In Family: 7 genera, +- 900 species: generally northern hemisphere. Note: Wood of Quercus critical for pre-20th century ship-building, charcoal for metallurgy; some now supply wood (Fagus, Quercus), cork (Quercus suber), food (Castanea, chestnut). Lithocarpus densiflorus moved to Notholithocarpus.
eFlora Treatment Author: John M. Tucker, except as noted
Genus: QuercusView DescriptionDichotomous Key

Common Name: OAK
Habit: Evergreen or not. Leaf: stipules small, generally early-deciduous. Staminate Inflorescence: catkins, 1--several, pendent, slender, proximal on twig. Pistillate Inflorescence: in distal leaf axils, short-stalked; flower generally 1. Staminate Flower: stamens 4--10. Pistillate Flower: calyx minute, generally 6-lobed; ovary enclosed by involucre. Fruit: nut 1, partly enclosed by cup-like involucre (cup) with appressed scales (nut and cup = acorn), remnants of perianth and style persistent as small point at tip; scales tubercled to not; mature in years 1 (on younger stems) or 2 (on older stems). Chromosomes: 2n=24.
Species In Genus: +- 600 species: northern hemisphere, to northern South America, India. Etymology: (Latin: ancient name for oak) Note: Many named hybrids; those (3) treated here form widespread populations; most others occur as single individuals, and some but not all of these are mentioned here, under the first parent treated (alphabetically). Reproduction of many species declining due to habitat degradation or loss as well as disease. Quercus robur added, as waif.
eFlora Treatment Author: Thomas J. Rosatti & John M. Tucker

Quercus douglasii Hook. & Arn.
NATIVE
Habit: Tree 6--20 m, deciduous; trunk bark checkered into thin scales, +- gray. Leaf: 3--6(8) cm; petiole 3--9 mm; blade oblong to obovate, adaxially dull, blue-green, abaxially puberulent, pale blue-green, tip generally rounded, margin +- entire, wavy, or +- lobed. Fruit: cup 12--20 mm wide, 6--10 mm deep, cup- to bowl-shaped, scales +- tubercled; nut 20--35 mm, ovoid to subcylindric, distally acute to +- obtuse, shell glabrous inside; mature in year 1.
Ecology: Dry slopes, interior foothills, woodland; Elevation: < 1590 m. Bioregional Distribution: KR, NCoRO, NCoRI, CaRF, SNF, Teh, ScV (Sutter Buttes), SnJV, SnFrB, SCoR, s ChI (Santa Catalina Island), WTR (n slope), MP. Flowering Time: Apr--May Note: Hybridizes with Quercus garryana (Quercus ×eplingii C.H. Mull.), Quercus john-tuckeri (Quercus ×alvordiana), Quercus lobata (Quercus ×jolonensis Sarg.).
eFlora Treatment Author: Thomas J. Rosatti & John M. Tucker
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Citation for this treatment: Thomas J. Rosatti & John M. Tucker 2016. Quercus douglasii, Revision 2, in Jepson Flora Project (eds.) Jepson eFlora, http://ucjeps.berkeley.edu/cgi-bin/get_IJM.pl?tid=40581, accessed on September 27, 2016.

Citation for the whole project: Jepson Flora Project (eds.) 2016. Jepson eFlora, http://ucjeps.berkeley.edu/IJM.html, accessed on September 27, 2016.


Quercus douglasii
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© 2008 Keir Morse
Quercus douglasii
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© 2008 Keir Morse
Quercus douglasii
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© 2013 Neal Kramer
Quercus douglasii
click for enlargement
© 2008 Keir Morse
Quercus douglasii
click for enlargement
© 2013 Neal Kramer
Quercus douglasii
click for enlargement
© 2015 Keir Morse

More photos of Quercus douglasii in CalPhotos


Geographic subdivisions for Quercus douglasii:
KR, NCoRO, NCoRI, CaRF, SNF, Teh, ScV (Sutter Buttes), SnJV, SnFrB, SCoR, s ChI (Santa Catalina Island), WTR (n slope), MP.
Markers link to CCH specimen records. Yellow markers indicate records that may provide evidence for eFlora range revision or may have georeferencing or identification issues. Purple markers indicate specimens collected from a garden, greenhouse, or other non-wild location.
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map of distribution 1
(Note: any qualifiers in the taxon distribution description, such as 'northern', 'southern', 'adjacent' etc., are not reflected in the map above, and in some cases indication of a taxon in a subdivision is based on a single collection or author-verified occurence).

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Data provided by the participants of the Consortium of California Herbaria.
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CCH collections by month

Duplicates counted once; synonyms included.
Species do not include records of infraspecific taxa.
Blue line denotes eFlora flowering time.