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Key to families | Table of families and genera

Specimen numbers are hyperlinked to records in the Consortium of California Herbaria data view where possible. Taxa are hyperlinked to entries in the Jepson Interchange via the "[Online Interchange]" link.


Evergreen or not. Leaf: stipules small, generally early-deciduous. Staminate inflorescence: catkins, 1–several, pendent, slender, proximal on twig. Pistillate inflorescence: in upper 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); scales tubercled to not; mature years 1 (on younger stems) or 2 (on older stems).
± 600 species: northern hemisphere, to northern South America, India. (Latin: ancient name for oak) [Manos et al. 1999 Molec Phylogen Evol 12:333–349] 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.
Unabridged references: [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.]

Key to Quercus

1. Acorn cup scales thin, not tubercled, shell hairy to woolly inside, at least at tip; bark dark gray or gray-brown to black

2. Leaf moderately to deeply lobed, lobes 1–4-toothed, teeth generally bristle-tipped; plant deciduous ..... Q. kelloggii

2' Leaf entire to toothed, teeth abruptly pointed to spine-tipped, not bristle-tipped; plant evergreen

3. Leaf adaxially convex, margin inrolled or not, obscuring marginal teeth, blade generally widely elliptic to round; fruit mature year 1 ..... Q. agrifolia

4. Leaf abaxially glabrous to sparsely hairy except vein axils hair-tufted ..... var. agrifolia

4' Leaf abaxially densely tomentose ..... var. oxyadenia

3' Leaf adaxially ± flat, margin not inrolled, blade generally lanceolate to oblong; fruit mature years 1–2

5. Leaf abaxially ± yellow or ± white woolly; fruit mature year 1 ..... Q. ilex

5' Leaf abaxially glabrous; fruit mature year 2

6. Leaf 2–5 cm, abaxially generally ± shiny, yellow-green; nut gradually tapered from below middle to tip ..... Q. wislizeni

7. Shrub 2–4(6) m ..... var. frutescens

7' Tree generally 10–22 m ..... var. wislizeni

6' Leaf 3–9(14) cm, abaxially generally ± dull ..... Q. parvula

8. Tree < 17 m — s North Coast, Inner North Coast Ranges, Central Western California (except Inner South Coast Ranges), Western Transverse Ranges ..... var. shrevei

8' Shrub 1–6 m

9. Leaf margin generally entire; Outer South Coast Ranges (Santa Barbara Co.), n Channel Islands (Santa Cruz Island), e Western Transverse Ranges ..... var. parvula

9' Leaf margin long-tapered dentate; San Francisco Bay Area (Mount Tamalpais) ..... var. tamalpaisensis

1' Acorn cup scales generally thick, generally tubercled to ± not, shell glabrous to woolly inside; bark light gray to ± white

10. Acorn nut shell ± woolly inside; fruit mature year 2; plants evergreen

11. Leaf generally 3–8 cm; acorn cup > 1.5 cm wide; generally tree, > 7 m

12. Leaf adaxially with lateral veins ± not impressed, abaxially golden-puberulent, glabrous in age ..... Q. chrysolepis

12' Leaf adaxially with lateral veins impressed, abaxially densely tomentose, sparsely tomentose in age — Channel Islands ..... Q. tomentella

11' Leaf generally 1–3.5 cm; acorn cup < 1.5 cm wide (if > 1.5 cm wide, leaves <= 3 cm); generally shrub, < 7 m

13. Twigs rigid; leaf margin wavy, strongly spine-toothed; blade elliptic to round-ovate; plants 2–6 m, erect ..... Q. palmeri

13' Twigs flexible; leaf margin entire to irregularly serrate, teeth mucronate or spine-tipped; blade oblong or lanceolate to ovate; plants to 5 m, prostrate to erect

14. Leaf margin entire or with few irregular spine-tipped teeth; dry chaparral, 100–1800 m, sw Peninsular Ranges ..... Q. cedrosensis

14' Leaf margin entire to mucro-toothed; montane conifer zone, 900–2800 m, Klamath Ranges, High North Coast Ranges, Inner North Coast Ranges, High Cascade Range, High Sierra Nevada, Modoc Plateau ..... Q. vacciniifolia

10' Acorn nut shell glabrous inside; fruit mature year 1; plants evergreen or not

15. Leaf lobed, margins generally without spines; plants deciduous

16. Leaf shallowly lobed (sinuses generally < 1/2 distance lobe tip to midrib), adaxially generally dull, green to blue-green

17. Leaf adaxially green; acorn cup scales tubercled; Channel Islands ..... Q. ×macdonaldii

17' Leaf adaxially blue- or gray-green; acorn cup scales ± tubercled; mainland

18. Shrub, tree < 3 m, evergreen to deciduous; leaves 1.5–5 cm, generally irregularly coarsely toothed, adaxially blue- or gray-green ..... Q. ×alvordiana (2)

18' Tree, deciduous; leaves 3–6(8) cm, ± entire, wavy, or ± lobed, adaxially blue-green ..... Q. douglasii

16' Leaf moderately to deeply lobed (sinuses generally > 1/2 distance lobe tip to midrib), adaxially ± shiny, dark green

19. Tree; acorn cup 10–30 mm deep, all scales tubercled; nut 30–50 mm, generally long-conic, tip pointed ..... Q. lobata

19' Shrub, tree; acorn cup 4–9 mm deep, lower scales ± tubercled, upper ± not; nut 20–30 mm, ovoid to ± spheric, tip rounded ..... Q. garryana

20. Tree, 8–20 m, generally with 1 trunk; terminal buds 5–12 mm, fusiform, hairs dense, ± yellow or ± white ..... var. garryana

20' Shrub, small tree, often < 5 m, generally with > 1 trunk; terminal buds 2–5 mm, hairs sparse, brown or ± red

21. Rays of stellate hairs on leaf abaxially generally 4–6, 0.25–0.5 mm; Klamath Ranges, High North Coast Ranges, Central Coast ..... var. breweri

21' Rays of stellate hairs on leaf abaxially generally 6–8, < 0.3 mm; Klamath Ranges, Inner North Coast Ranges, High Cascade Range, Sierra Nevada (except c High Sierra Nevada), San Francisco Bay Area, Outer South Coast Ranges, ne Western Transverse Ranges, Modoc Plateau ..... var. semota

15' Leaf generally entire to toothed, not lobed, teeth with spines or not; plants generally evergreen

22. Leaves 7–11(18) cm, serrate, lateral veins of larger leaves generally 20–28, generally straight and prominent; stipules persistent, > 10 mm, silky-hairy ..... Q. sadleriana

22' Leaves 1–6 cm, entire to dentate, lateral veins of larger leaves generally < 20, generally not straight and prominent; stipules early-deciduous, < 10 mm, not silky-hairy

23. Tree generally > 5 m; leaves 2–6 cm, oblong to obovate, entire or ± toothed, adaxially green to blue-green

24. Shrub to small tree, 5–6(10) m; leaf blade (10)20–35(60) mm, adaxially shiny green to dull blue-green, margin entire, dentate, or wavy-dentate ..... Q. ×acutidens (2)

24' Tree, 5–18 m; leaf blade (20)30–60(80) mm, adaxially blue-green, dull, margin wavy-dentate to generally entire ..... Q. engelmannii

23' Shrub generally < 5 m; leaves 1–5 cm, elliptic to ovate or ± round, variously toothed, adaxially generally green

25. Leaf 2-colored, adaxially yellow- to gray-green, abaxially ± white, densely fine-tomentose, hairs obscuring lateral veins ..... Q. cornelius-mulleri

25' Leaf 1–2-colored, adaxially green to gray- or blue-green, abaxially generally green, not densely tomentose, hairs not obscuring lateral veins

26. Leaf generally oblong to obovate, margin wavy to obtuse-toothed; Peninsular Ranges ..... Q. ×acutidens (2)

26' Leaf elliptic to ovate or ± round, margin toothed, teeth abruptly pointed to spine-tipped

27. Acorn cup thin, scales ± tubercled to not; leaf adaxially gray- or blue-green, dull

28. Acorn stalk 10–15 mm, nut cylindric-ovoid to elliptic, abruptly tapered to tip, 12–23 mm, generally yellow-brown; leaves oblong to elliptic, generally regularly spine-toothed ..... Q. turbinella

28' Acorn stalk 0, nut conic-ovoid, gradually tapered to tip, 20–40 mm, generally dark brown; leaves oblong to elliptic or obovate, irregularly toothed, teeth blunt to weakly spiny

29. Shrub, tree < 3 m; leaves 1.5–5 cm, toothed but not spine-toothed, adaxially blue- to gray-green ..... Q. ×alvordiana (2)

29' Shrub; leaves 1.3–2.8 cm, spine-toothed, adaxially gray-green ..... Q. john-tuckeri

27' Acorn cup thick, scales tubercled; leaf adaxially generally green, ± shiny (dull or not in Quercus durata)

30. Leaf adaxially dull, convex, margin often inrolled, obscuring teeth ..... Q. durata

31. Leaf adaxially strongly convex, abaxially short-hairy when young; generally on serpentine, North Coast Ranges, n Sierra Nevada, n Central Coast, San Francisco Bay Area, South Coast Ranges ..... var. durata

31' Leaf adaxially ± convex, abaxially densely short-hairy when young; not on serpentine, se Western Transverse Ranges, San Gabriel Mountains (s slope) ..... var. gabrielensis

30' Leaf adaxially ± shiny, flat to ± wavy, not convex, margin generally not inrolled

32. Leaf abaxially with spreading, 2–6-rayed hairs — South Coast, Peninsular Ranges, chaparral or coastal-sage scrub, < 200 m ..... Q. dumosa

32' Leaf abaxially with appressed, 4–10-rayed hairs

33. Leaf base wedge-shaped or generally truncate or rounded; margin mucro- or spine-toothed; widespread on mainland ..... Q. berberidifolia

33' Leaf base gradually tapered, wedge-shaped, or rounded; margin entire, wavy, or ± toothed, teeth generally mucronate; Channel Islands ..... Q. pacifica


Citation for the whole project: Jepson Flora Project (eds.) [year] Jepson eFlora, [accessed on month, day, year]
Citation for an individual treatment: [Author of taxon treatment] [year]. [Taxon name] in Jepson Flora Project (eds.) Jepson eFlora, [URL for treatment]. Accessed on [month, day, year].
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