Flora of North America species comparison

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Quercus pacifica

Quercus muehlenbergii

Channel Island scrub oak, island scrub oak, Pacific oak

Chinkapin oak, chinquapin oak, yellow chestnut oak
Habit Shrubs, rarely small trees, subevergreen, shrubs to 2 m, trees to 5 m or taller. Trees, deciduous, moderate to large, to 30 m, occasionally large shrubs (ca. 3 m) on drier sites.
Bark

scaly on older branches and trunk.

gray, thin, flaky to papery.
Twigs

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

brownish, 1.5-3(-4) mm diam., sparsely fine-pubescent, soon becoming glabrate, graying in 2d year.
Buds

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

brown to red-brown, subrotund to broadly ovoid, 20-40 × (10-)15-25 mm, apex rounded, very sparsely pubescent.
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 usually obovate, sometimes lanceolate to oblanceolate, (32-)50-150(-210) × (10-)40-80(-106) mm, leathery, base truncate to cuneate, margins regularly undulate, toothed or shallow-lobed, teeth or lobes rounded, or acute-acuminate, often strongly antrorse, secondary veins usually (9-)10-14(-16) on each side, ± parallel, apex short-acute to acuminate or apiculate;

surfaces abaxially glaucous or light green, appearing glabrate but with scattered or crowded minute, appressed, symmetric, 6-10-rayed stellate hairs, adaxially lustrous dark green, glabrate.
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.

1-2, subsessile or on axillary peduncle to 8 mm;

cup hemispheric or shallowly cupped, 4-12 mm deep × 8-22 mm wide, enclosing 1/4-1/2 nut, base rounded, margin usually thin, scales closely appressed, moderately to prominently tuberculate, uniformly short gray-pubescent;

nut light brown, oblong to ovoid, (13-)15-20(-28) × 10-13(-16) mm.
Cotyledons

distinct.

distinct.
2n

= 24.

Quercus pacifica

Quercus muehlenbergii
Phenology Flowering spring. Flowering late winter–spring.
Habitat Chaparral, oak woodlands, margins of grasslands, understory in closed-cone pine stands Mixed deciduous forest, woodlands and thickets, sometimes restricted to n slopes and riparian habitats in w parts of range, limestone and calcareous soils, rarely on other substrates
Elevation 0-300 m (0-1000 ft) 0-2300 m (0-7500 ft)
Distribution
from FNA
CA
[WildflowerSearch map]
[BONAP county map]
from FNA
AL; AR; CT; FL; GA; IA; IL; IN; KS; KY; LA; MA; MD; MI; MN; MO; MS; NC; NE; NJ; NM; NY; OH; OK; PA; SC; TN; TX; VA; VT; WI; WV; ON; Mexico (Coahuila, Nuevo León, Hidalgo, and Tamaulipas)
[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.)

Shrubby forms of Quercus muhlenbergii are difficult to distinguish from Quercus prinoides, but Q. muhlenbergii does not spread clonally or produce acorns on small shrubs as does Q. prinoides. The edaphic preferences of these two species are distinctive, with Q. muhlenbergii never far from limestone substrates and Q. prinoides occurring mostly on dry shales and deep sands. Populations of Q. muhlenbergii from the southwest part of its range, on the Edwards Plateau of Texas and westward, sometimes are segregated as Q. brayi Small, but the variation appears to be clinal with inconsistent differences. Distributed from Hidalgo, Mexico to Maine, Q. muhlenbergii is one of the most widespread species of temperate North American trees.

The Delaware-Ontario prepared infusions from the bark of Quercus muhlenbergii to stop vomiting (D. E. Moerman 1986).

(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. 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. 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. dumosa var. polycarpa Q. acuminata, Q. brayi, Q. prinus var. acuminata
Name authority Nixon & C. H. Muller: Novon 4: 391. (1994) Engelmann: Trans. Acad. Sci. St. Louis 3: 391. (1887)
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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