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Vascular Plants of California
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Quercus robur

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
Scientific Editor: Thomas J. Rosatti, Bruce G. Baldwin.
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
Reference: Manos et al. 1999 Molec Phylogen Evol 12:333--349
Unabridged Reference: Cottam, W. P., J. M. Tucker, & F. S. Santamour. 1982. Oak hybridization at the University of Utah. State Arboretum of Utah Publication No. 1. Salt Lake City; Hardin, J. W. 1975. Hybridization and introgression in Quercus alba. Journal of the Arnold Arboretum 56: 336--363; Manos, P. S., Doyle, J. J., & Nixon, K. C. 1999. Phylogeny, biogeography, and processes of molecular differentiation of Quercus subgenus Quercus (Fagaceae). Molec Phylogen Evol 12: 333--349.
Quercus robur L.
Habit: Tree < 30 m, deciduous; trunk bark scaly, light gray. Leaf: (5)7--15(20) cm; petiole 3--6 mm; blade obovate to narrow-elliptic or -obovate, adaxially shiny or dull, deep to light green or gray, abaxially glabrous (in youth sometimes sparsely hairy), light green, base strongly cordate, often revolute, tip widely rounded, margin lobes 6--12 per leaf, deep (sinuses 1/3--7/8 distance lobe tip to midrib), rounded, generally coarsely 2-toothed at tip. Fruit: cup 13--20 mm wide, 8--10 mm deep, hemispheric to deeply goblet-shaped, scales +- not tubercled; nut 15--30(35) mm, 12--20 mm wide, ellipsoid or oblong, distally obtuse to rounded, shell woolly inside; mature in year 1.
Ecology: Roadsides, pastures, forest margins, woodlands, persisting near old homesites; Elevation: < 1000 m. Bioregional Distribution: s SnFrB (Santa Cruz Mountains); Distribution Outside California: Washington, British Columbia to Prince Edward Island; native to Europe. Flowering Time: Mar--Apr Note: Cordate leaf base distinctive, evidently dominant, present in hybrids. Very important in furniture, previously in sailing ships. Hybridizes with Quercus lobata; hybridized artificially with Quercus turbinella; hybrids with Quercus ilex (Quercus ×turneri Willd.) in cultivation but evidently not in nature despite occurring together.
Synonyms: Quercus pedunculata Ehrh.
Unabridged Note: Hybrids reported with a number of taxa that have not been reported from California: Quercus alba L. (Quercus ×bimundorum E.J. Palmer); Quercus bicolor Willd. (Quercus ×warei T.L. Green & W.J. Hess); Quercus cerris L.; Quercus faginea Lam.; Quercus frainetto Ten.; Quercus humilis DC.; Quercus macrocarpa Michx. (Quercus ×macdanielii T.L. Green & W.J. Hess); Quercus mongolica Fisch. ex Ledeb.; Quercus petraea (Matt.) Liebl. (Quercus ×rosacea Bechst.); Quercus pyrenaica Willd. (Quercus ×andevagensis Hy 1895, Quercus ×henriquesii Franco & Vasc. 1954).
Jepson eFlora Author: Thomas J. Rosatti & John M. Tucker
Reference: Manos et al. 1999 Molec Phylogen Evol 12:333--349
Index of California Plant Names (ICPN; linked via the Jepson Online Interchange)

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Citation for this treatment: Thomas J. Rosatti & John M. Tucker 2014, Quercus robur, in Jepson Flora Project (eds.) Jepson eFlora, Revision 2,, accessed on June 22, 2021.

Citation for the whole project: Jepson Flora Project (eds.) 2021, Jepson eFlora,, accessed on June 22, 2021.

No expert verified images found for Quercus robur.

Geographic subdivisions for Quercus robur:
s SnFrB (Santa Cruz Mountains)
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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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All markers link to CCH specimen records. The original determination is shown in the popup window.
Blue markers indicate specimens that map to one of the expected Jepson geographic subdivisions (see left map). Purple markers indicate specimens collected from a garden, greenhouse, or other non-wild location.
Yellow markers indicate records that may provide evidence for eFlora range revision or may have georeferencing or identification issues.

CCH collections by month

Duplicates counted once; synonyms included.
Species do not include records of infraspecific taxa, if there are more than 1 infraspecific taxon in CA.
Blue line denotes eFlora flowering time (fruiting time in some monocot genera).