Quercus turbinella Greene

by Susan Bean, Native Plants of Arizona 2007
Common names: Sonoran scrub oak (1), shrub live oak, encino achaparrado, scrub oak (2), California scrub oak, turbinella oak, Tucker’s oak (3).
Family: Fagaceae (1)
subfamily: Fagoideae (4)
Synonymy: Quercus dumosa Nutt. var. turbinella (Greene) Jepson (1), Quercus turbinella var. ajoensis (3), Quercus dumosa Nuttall var. turbinella (Greene), Jepson; Q. subturbinella Trelease (5).
Etymology: Quercus is classical Latin for oak, possibly derived from the Celtic quer, "fine," and cuez, "tree" (6); turbinella: shaped like a spinning top (6), referring to the acorn cupule (7).

Identification
Growth form: Clump-forming evergreen shrub or small tree. Typically from 1-2 m. in height with stem diameters to 20 cm but can reach 5 m or more (3). Much-branched with a spreading crown (7).
Roots: Sprouts from rhizomes, forming colonies. Roots and rhizomes may spread 4.9 m or more horizonally. Thousands of stems may form from a single or a few individuals. Top foot of soil typically a dense network of small laterals that aid in absorption of moisture. Roots over 8 m deep reported in parts of Arizona (3).
Stem: Bark light gray or brown, scaly. Twigs brown to gray, 1-3 mm diameter, usually tomentulose, sometimes glabrous, becoming glabrate (5). Rigid branches (7)
Leaves: Leaves highly variable (8). Bluish-green with bloom (powdery surface); nearly hairless above, yellowish green and finely haired beneath; elliptical to oblong, thick, stiff; margins have small, spinelike teeth; evergreen (9). Leathery leaves are 1.3-4 cm long, 0.7-2.4 cm wide (3).  Petiole 1-4 mm. Leaf margins planar or slightly crisped-undulate, coarsely 3-5-toothed or very shallowly lobed on each side, teeth spinose with spines 1-1.5 mm, secondary veins 4-8 on each side (5). Holly-like leaves unfold a reddish color and change to shiny lime-green before becoming blue and bloomy. The leaves remain on the shrub all year until pushed off by new growth (7).
Inflorescence/flowers: Flowers are tiny. Male and female flowers on same tree. Male in drooping catkin, female in short spike (9).
Fruit: Brownish, narrow, pointed acorn in shallow, scaly cup (9) Annual acorns 1.3-2.5 cm long with turbinate cups (3). Acorns solitary or several, on axillary peduncle 10-40 mm; cup hemispheric or shallowly cup-shaped, 4-6 mm deep × 8-12 mm wide, covering 1/4-1/2 of the nut, scales tightly appressed, ovate, grayish or yellowish; nut light brown, ovoid, to 20 × 11 mm. Cotyledons distinct (5).
Similar species: Quercus turbinella is distinguished by its spiny-toothed, thick, stiff leaves with whitish bloom (powdery appearance) (9); it forms putative hybrid swarms with Q . gambelii as well as with Q. grisea (5).

Ecology

Life history: Perennial shrub to tree (1).
Native/introduced: Native to southwestern United States (1).
Phenology: Flowers April through June. Acorns mature in summer or early fall. At one Arizona site, acorns present from late August to early September. Tree is associated with monsoon pattern and acorns often germinate during summer rainy period (3).
Distribution: Occurs in every county in Arizona (1) as well as in California, Colorado, New Mexico, Nevada, Texas, Utah, northern and Baja Mexico (5). Found in semiarid, lower elevation chaparral, pinyon-juniper, shrub deserts, oak woodlands, ponderosa pine, and riparian communities. Often grows in scattered patches in swales and canyons. A dominant shrub in Arizona chaparral, frequently comprising up to 50% of shrub cover. Drought tolerant, often grows on warm, dry, southern exposures in northern part of range. (3)

Uses: The Hualapai use the acorns to make bread, stew, and mush; they also also eat the acorns roasted. The Gila River Pima eat the acorns raw. The Cocopa gather the acorns for trade with the Paipai for sheep skins. The Havasupai use the wood for hoe and axe handles (10).

The leaves are valuable browse and emergency winter or drought food for wildflife in southern and central Arizona (3). Quercus turbinella can survive heavy browsing and may remain as almost the only forage on deteriorated ranges in Arizona. New, succulent growth is most palatable. Mule deer and desert bighorn sheep browse on Q. turbinella in Arizona, as do cattle, domestic sheep, and domestic goats. The acorns are eaten by cattle, collared peccary, wild turkey, mule deer, numerous rodents, geese, grouse, quail, scrub jays, and many other birds. The cambium is eaten by sapsuckers, the bark by porcupines, and the twigs by beavers. Quercus turbinella thickets provide cover for wide range of birds and mammals (3).

Notes: Chaparro is Spanish for live oak. Chaparral is derived from chaparro (6).  Greene, Edward Lee, 1843-1915: Botanist in Colorado, California, New Mexico. Authored hundreds of botanical articles and history of botany. Lecturer at University of California at Berkeley, Curator of Herbarium at California Academy of Sciences, Professor and Chair of new Botany Department in 1891.  Became Associate of the Smithsonian. Pre-eminent taxonomic splitter, proposing around 3000 new specific names during his life (11).

References

1.  USDA, NRCS. The PLANTS Database (http://plants.usda.gov, 12 October 2007). National Plant Data Center, Baton Rouge, LA 70874-4490 USA.

2. Elmore, F.H. 1976. Shrubs and Trees of the Southwest Uplands. Southwest Parks and Monuments Association. Globe, Arizona.

3. Tirmenstein, D. 1999. Quercus turbinella. In: Fire Effects Information System, U.S. Department of Agriculture, Forest Service, Rocky Mountain Research Station, Fire Sciences Laboratory (Producer). (http://www.fs.fed.us/database/feis/ 2007, October 13].

4. USDA Germplasm Resources Information Network. (http://www.ars-grin.gov, 12 October 2007). Agricultural Research Service, Beltsville Area.

5. Flora of North America. 2007. Flora of North America Association. (http://www.efloras.org, 12 October 2007).

6. Charters, M. 2007. Calflora Botanical Names.  (http://www.calflora.net/botanical names, 12 October 2007

7. NATIVE PLANT DATABASE (http://www.wildflower.org/plants, 12 October 2007). Lady Bird Johnson Wildflower Center, University of Texas at Austin.

8. Ayers, T. 2007. Spoken communication 10-2-07.

9. Epple, Anne Orth. 1995. A Field Guide to the Plants of Arizona. Falcon Press. Helena, Montana.

10. Moerman, D. Native American Ethnobotany Database (http://herb.umd.umich.edu/, 12 October 2007). University of Michigan, Dearborn

11. Schneider, A. and B. 2001–2007. Wildflowers, Ferns, and Trees 
of the
Four Corners Region of 
Colorado, New Mexico, Arizona, & Utah. www.swcoloradowildflowers.com