Flora of North America species comparison

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Quercus pacifica

Quercus montana

Channel Island scrub oak, island scrub oak, Pacific oak

chestnut oak, mountain chestnut oak, rock chestnut oak
Habit Shrubs, rarely small trees, subevergreen, shrubs to 2 m, trees to 5 m or taller. Trees, deciduous, to 30 m. Bark dark gray or brown, hard, with deep V-shaped furrows.
Bark

scaly on older branches and trunk.

Twigs

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

light brown, 2-3(-4) mm diam., glabrous.
Buds

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

light brown, ovoid, (3-)4-6 mm, occasionally apex acute, 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 obovate to narrowly elliptic or narrowly obovate, (100-)120-200(-220) × 60-100(-120) mm, base subacute or rounded-acuminate, often unequal, margins regularly toothed, teeth rounded or rarely somewhat acute, secondary veins ± parallel, straight or moderately curved, 10-14(-16) on each side, apex broadly acuminate;

surfaces abaxially light green, appearing glabrous but with scattered minute, asymmetric, appressed-stellate hairs and usually visible, larger, simple or fascicled erect hairs along veins, adaxially dark green, glossy, glabrous or with minute, scattered, simple hairs.
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.

1-3, subsessile or on peduncle 8-20(-25) mm;

cup shallowly cup-shaped to hemispheric or deeply goblet-shaped, rim thin, often flared and undulate, helmetlike, 9-15 mm deep × 18-25 mm wide, scales often in concentric or transverse rows, laterally connate, gray, broadly ovate, tips reddish, glabrous;

nut light brown, ovoid-ellipsoid, 15-30 × 10-20(-25) mm, glabrous.
Cotyledons

distinct.

distinct.
2n

= 24.

Quercus pacifica

Quercus montana
Phenology Flowering spring. Flowering mid-late spring.
Habitat Chaparral, oak woodlands, margins of grasslands, understory in closed-cone pine stands Rocky upland forest, dry ridges, mixed deciduous forests on shallow soils
Elevation 0-300 m (0-1000 ft) 0-1400 m (0-4600 ft)
Distribution
from FNA
CA
[WildflowerSearch map]
[BONAP county map]
from FNA
AL; CT; DE; GA; IL; IN; KY; MA; MD; ME; MI; MS; NC; NH; NJ; NY; OH; PA; RI; SC; TN; VA; VT; WV
[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.)

The name Quercus prinus Linnaeus is often applied to this species, particularly in the forestry literature, and in many regional floras. In a number of works, however, Q. prinus has been applied to the species here treated as Q. michauxii. Following the recommendations of J. W. Hardin (1979), because of the persistent confusion in the application of the name Q. prinus and uncertainty regarding the identity of the Linnean type materials, the names Q. montana and Q. michauxii should be used for the two species that have been variously called Q. prinus. Quercus prinus under this interpretation is a name of uncertain position.

The four species of the chestnut oak group in eastern North America (Quercus montana, Q. michauxii, Q. muhlenbergii, and Q. prinoides) are somewhat difficult to distinguish unless careful attention is paid to features of leaf vestiture and fruit and cup morphology. Attempts to identify these species mostly or solely on basis of leaf shape and dentition (as in many other oak species complexes) have resulted in a plethora of misidentified material in herbaria and erroneous reports in the literature. The closely appressed, asymmetric trichomes on the abaxial surface of the mature leaf, in combination with longer simple hairs along the midvein, are unique to Q. montana among North American species of Quercus. Immature leaves and densely shaded leaves sometimes exhibit a more erect trichome that could be confused with the longer, felty hairs of Q. michauxii, so it is important to evaluate mature sun leaves when possible.

(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. 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. 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
Name authority Nixon & C. H. Muller: Novon 4: 391. (1994) Willdenow: Sp. Pl. 4(1): 440. (1805)
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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