Flora of North America species comparison

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Quercus pacifica

Quercus sinuata

Channel Island scrub oak, island scrub oak, Pacific oak

bastard oak, bastard white oak, Durand oak, Durand white oak
Habit Shrubs, rarely small trees, subevergreen, shrubs to 2 m, trees to 5 m or taller. Trees or shrubs, deciduous, to 15(-20) m, with solitary or multiple trunks.
Bark

scaly on older branches and trunk.

gray to light brown, flaky to papery and exfoliating.
Twigs

brownish or reddish, minutely puberulent, becoming glabrate and gray with age.

light gray or gray, 1-2(-3) mm diam., glabrous, rarely minutely puberulent.
Buds

light or chestnut brown, ovate or globose, 2-3 × 1-2 mm.

brown or reddish brown, broadly ovoid, 2-3 mm, essentially glabrous.
Leaves

blade obovate or oblong, planar to moderately convex or undulate, 15-40 × 7-20(-40) mm, base cuneate or rounded, attenuate-decurrent along petiole, margins minutely cartilaginous, entire or with 1-5 irregular teeth on each side, secondary veins obscure, 1-5 on each side, apex blunt or rounded, occasionally subacute with mucronate tip;

surfaces abaxially waxy, glandular, with scattered minute, flat, appressed, ± 8-rayed stellate hairs, not obscuring surface, adaxially green, glossy, glabrate or with minute, scattered, stellate hairs.

blade oblong to oblanceolate, or narrowly rhomboid, or cuneiform, or rounded-3-dentate, (25-)30-120(-140) × (15-)25-60 mm, base acute, cuneate, attenuate-rounded, or obtuse, margins entire to irregularly toothed or moderately, sinuately lobed, flat, secondary veins ca. 7-11 on each side, apex broadly rounded, rarely attenuately narrowed or obscurely 3-lobed;

surfaces abaxially silvery or dull green, with scattered to crowded, minute, appressed-stellate, 8-10-rayed hairs, or glabrate or glabrous, especially in shade forms, adaxially green or dull green, glabrous.
Acorns

paired or solitary in leaf axil, subsessile, rarely pedunculate in teratological forms;

cup hemispheric to turbinate, to 15 mm deep × 20 mm wide, enclosing only 1/4-1/2 nut, scales moderately to heavily tuberculate, irregularly formed;

nut light brown, acute-cylindric or fusiform, tapered, (15-)20-30 × (6-)9-15 m, apex acute, glabrate.

solitary or paired, subsessile or on axillary peduncle to 1-7 mm;

cup saucer-shaped to shallowly cup-shaped, rarely deeper, 2-8 mm deep × 8-15(-20) mm wide, enclosing 1/8-1/4 nut, rarely more, base flat, rounded, or constricted, margin thin, scales closely appressed, grayish with reddish margins, ovate, flat, obtuse, not tuberculate;

nut light brown, depressed-ovoid to oblong, 7-15 × 7-12(-17) mm, glabrous.
Cotyledons

distinct.

distinct.

Quercus pacifica

Quercus sinuata
Phenology Flowering spring.
Habitat Chaparral, oak woodlands, margins of grasslands, understory in closed-cone pine stands
Elevation 0-300 m (0-1000 ft)
Distribution
from FNA
CA
[WildflowerSearch map]
[BONAP county map]
from FNA
AL; AR; FL; GA; LA; MS; NC; OK; SC; TX
[WildflowerSearch map]
[BONAP county map]
Discussion

Of conservation concern.

Quercus pacifica is endemic on three of the California Channel Islands: Santa Cruz, Santa Catalina, and Santa Rosa. It is not known from the mainland, but it bears a superficial similarity to some of the tree forms that are putative hybrids between Q. engelmannii and Q. cornelius-mulleri in San Diego County. The latter populations, sometimes treated as Q. ×acutidens, differ in having much greater variability in leaf shape; thicker, more leathery leaves; denser abaxial leaf vestiture; much smaller hairs, having more than 10 rays; and variable levels of connation of cotyledons (always distinct in Q. pacifica). Quercus pacifica appears to be most closely related to Q. douglasii, whether by direct descent or by introgression with another species no longer extant on the islands.

Quercus ×macdonaldii Greene (as a species) [= Quercus dumosa var. macdonaldii (Greene) Jepson] is a stabilized hybrid complex between Quercus pacifica and Q. lobata Née. The plants tend to be small to moderate trees with leaves that resemble those of Q. lobata; the leaves are much more shallowly lobed and always less than two-thirds the distance from the margin to the midrib. Quercus ×macdonaldii is known from Santa Rosa, Santa Cruz, and Santa Catalina islands.

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

Varieties 2 (2 in the flora).

The question of the correct name for this species has persisted, with some authors rejecting the usage here in favor of Quercus durandii. Although no type material is extant, the original description of Q. sinuata is consistent with the concept presented here, as by W. W. Ashe (1916) and W. Trelease (1924), and inconsistent with any other oak from the broad area covered by Thomas Walter's Flora Caroliniana (1788).

The two varieties differ in habit, habitat, leaf size and lobing, and geographic range, and considerable variability exists within both varities as to the degree and density of silvery stellate-pubescence on the abaxial surface of the leaf. Sun leaves of both tend to have a higher proportion of silvery pubescence, and shade leaves and some individual trees tend to have more glabrate leaves, although evidence of flat-stellate trichomes is usually apparent. Plants with young, expanding leaves sometimes are mistaken for Quercus nigra, a member of the red oak group.

(Discussion copyrighted by Flora of North America; reprinted with permission.)
Key
1. Trees to 20 m, trunk usually solitary; moist bottomlands and riparian habitats.
var. sinuata
1. Shrubs or small trees to 3(–5) m, often forming thickets, trunks multiple from near ground; dry limestone hills.
var. breviloba
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. 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. 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. 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. 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. stellata, Q. tardifolia, Q. texana, Q. tomentella, Q. toumeyi, Q. turbinella, Q. vacciniifolia, Q. vaseyana, Q. velutina, Q. viminea, Q. virginiana, Q. wislizenii
Subordinate taxa
Q. sinuata var. breviloba, Q. sinuata var. sinuata
Synonyms Q. dumosa var. polycarpa Q. durandii
Name authority Nixon & C. H. Muller: Novon 4: 391. (1994) Walter: Fl. Carol., 235. (1788)
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).



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