Quercus ilicifolia Wang. - Bear Oak, Scrub Oak
Native , Common
By Steven D. Glenn
Not peer reviewed
Last Modified 01/25/2013
Common NamesBear Oak, Scrub Oak
Field IdentificationDeciduous shrub with alternate, simple, lobed leaves; leaf undersides white-gray; buds clustered near twig ends; catkin-like flowers in spring followed by acorns in the fall.
Disclaimer: The information provided here is for reference and historical use. We do not recommend nor do we condone the use of this species for medicinal purposes without first consulting a physician.Used by Native Americans to treat "female troubles". (Moerman, 1998)
Other usesOak-mast surveys may help wildlife agencies better understand dynamics of fall harvests and may be useful in harvest management models that attempt to stabilize fall harvest rates of game animals (Norman, 2003).
Tannins derived from oaks have been used historically to tan animal hides into leather. (Burrows & Tyrl, 2001)
Oak leaves, buds, bark, and acorns contain tannins which have varying degrees of toxicity in different animals. Although oak foliage and acorns provide valuable food for many wildlife species and even some livestock, oak toxicosis, a urinary and digestive tract disease can occur when some animals are forced to subsist on oaks exclusively for several days. Poisoning is rare in humans due to the large amounts needed to ingest to cause symptoms. (Burrows & Tyrl, 2001)
Dryads (or "tree spirits") are nymphs associated with Greek mythology which live near, or in, trees. Dryads are born bonded to a specific tree, originally, in the Indo-European Celtic-Druidic culture, an oak tree. Drys in Greek signifies 'oak,' from an Indo-European root *derew(o)- 'tree' or 'wood.'
In a nationwide vote hosted by the National Arbor Day Foundation in 2001, the oak was selected as America's National Tree.
NomenclatureQuercus ilicifolia Wang., Beytr. Teutsch. Holzg. Forstwiss. Nordam. Holz. 79, pl. 6, fig. 17. 1787.
?Quercus pumila W. Young, Cat. Arb. Arbust. Am. 20. 1783.
Quercus nigra pumila Marsh., Arbust. Am. 122. 1785.
Quercus rubra nana Marsh., Arbust. Am. 123. 1785.
Quercus banisteri Michx., Hist. Chenes Amer. no. 15, t. 27. 1801.
Quercus discolor (Q. banisteri) Spach, Hist. Nat. Veg. Phan. 11: 164. 1842.
Quercus nigra var. ilicifolia (Wangh.) Kuntze, Rev. Gen. Pl. 2: 642. 1891.
Quercus nana (Marsh.) Sarg., Gard. & For. 8: 93. 1895.
Quercus pumila (Marsh.) Sudw., U.S. Dept. Agric. For. Serv. Bull. 14: 172. 1897.
HABIT Perennial, deciduous, phanerophytic, shrub, diclinous and monoecious, normally 2-6 m tall; one specimen estimated at 10m in Washington County, Rhode Island, 1927 (Eaton, 1928).
STEMS Main stems ascending or erect, round. Bark gray or dark gray, shallowly fissured and scaly, not exfoliating. Branches erect or ascending or horizontal. Twigs dark brown or brown or gray, fluted-terete, 2-4 mm in diameter, smooth and lenticellate, 1st year twigs densely covered with fasciculate erect or spreading brown to light brown hairs, hairs becoming less dense and turning light gray on 2nd-3rd year twigs; glabrous on older twigs. Pith white, 5-pointed, continuous, nodal diaphragm absent. Sap translucent. For an anatomical study of the xylem see Tillson & Muller, 1942.
BUDS Terminal and axillary present, clustered at twig apices and scattered along stem, usually densely brown or gray hairy for most of their length. Terminal bud ovoid, semi-pointed; axillary buds ovoid, semi-pointed. Bud scales dark reddish-brown or brown, imbricate, with short and unbranched appressed brown or light brown hairs, sparsely distributed. Bud scale scars encircling the twig. Leaf scars crescent or half-round shaped. Vascular bundle scars numerous, scattered.
LEAVES Alternate, simple, (appearing pseudo-opposite or pseudo-whorled at twig apices), crowded toward stem apex or spaced somewhat evenly along and divergent from stem. Stipules lateral, free from the petiole, linear, caducous. Petiole adaxially flattened, .5-2.5 cm long, with brown to light brown fasciculate erect to spreading hairs, moderately densely or densely distributed throughout. Leaf blades: abaxial surface light gray to light gray-green (due to dense covering of tomentum); adaxial surface green to dark green, often glossy; elliptic or ovate or obovate, bilaterally symmetric, 3.5-12 cm long, 2-10 cm wide, chartaceous; base obtuse or cuneate or occasionally truncate; margins somewhat symmetrically 2-3 lobed per side, 1/8-1/2 distance to the midvein with rounded shallow sinuses and acute or obtuse, aristate apices; apex acute and aristate. Abaxial surface usually exhibits the following hair types: a. fasciculate brown to light brown erect to spreading hairs, moderately distributed along the midvein; b. simple brown to light brown erect hairs, sparsely to moderately distributed mainly along the main veins; c. minute simple yellowish more or less appressed multi-cellular glandular hairs, sparsely to moderately distributed throughout; d. tufted multi-radiate light gray (occasionally light brown) hairs densely distributed throughout. Adaxial surface with all aforementioned hair types when young, retaining only sparsely scattered multi-radiate hairs when mature (these minute, surface appearing glabrous with naked eye), see Hardin, 1979a;Thompson & Mohlenbrock, 1979; and for an overview of the phenology and the variability and density of hairs due to ecological factors and hybridization see Hardin, 1979b.
FEMALE INFLORESCENCES Coetaneous, spike consisting of a single flower (sometimes 2-3), in axils of current year leaves, subsessile initially, often becoming short-pedunculate in fruit, surrounded by a cupule which is persistent, accrescent, and indurate in fruit (acorn cap). There has been debate over the years regarding the true ontogenetic nature of the cupule. Originally thought to be an involucre of bracts, recent research suggests that the cupule is a complex partial inflorescence derived from stem tissue, see Abbe, 1974;Brett, 1964;Foreman, 1966;MacDonald, 1979;Fey & Endress, 1983. Each cupule subtended by 3 minute, caducous bracteoles. For an investigation of the influence of micro topography and stem height on floral sex ratios see Aizen & Kenigsten, 1990.
FEMALE FLOWERS Perianth of one whorl, minute, fragrance absent. Calyx urceolate, of fused sepals. Carpels 3. Locules 3, each containing 2 ovules. Styles 3, each with 1 stigma. Ovary inferior. Placentation axile. For an investigation of embryogenesis see Stairs, 1964.
MALE INFLORESCENCES Coetaneous, compound, solitary or fascicled spikes; pendant, catkin-like; in leaf axils of previous year. Rachis densely covered with brown hairs; elongating with age; with 1 subsessile or sessile flower per node, each flower subtended by a small, sessile caducous bracteole. For an investigation of the influence of micro topography and stem height on floral sex ratios see Aizen & Kenigsten, 1990.
MALE FLOWERS Perianth of one whorl, fragrance absent. Calyx actinomorphic, campanulate, of fused sepals. Sepal lobes 3-4, broadly oval to ovate with brown hairs moderately dense distributed throughout. Stamens 3-7, exserted. Anthers glabrous, basifixed, opening along the long axis. Filaments free, 1mm long, straight, glabrous. For a review of pollen morphology see Solomon, 1983a. For an investigation of microsporogenesis see Stairs, 1964.
FRUITS Acorn (glans (Spjut, 1994)) (calybium (Kaul, 1985)) sessile to short-pedunculate; maturation biennial. Acorn ovoid-subglobose, 1-1.7 cm long, comprised of 2 parts- a. the acetabuliform-crateriform cup (cupule), enclosing 1/4-1/2 of the base of the nut; and b. the nut, 1-seeded by abortion. For a hypothesis that the first ovule fertilized suppresses the normal development of the others see Mogensen, 1975. Cupule exterior composed of imbricate, appressed scales moderately covered with brown tomentum. Nut olive-green to brown, ovoid-subglobose, with large light-colored circular cupule scar at base and apiculate at the distal end, initially with minute short and unbranched appressed brown to light brown hairs, sparsely distributed throughout, glabrescent, minutely laterally striate. One study found a size range of .15-1.24 cubic cm with a mean of 0.60 cubic cm and a correlation between smaller acorn size with increasing latitude see Aizen & Woodcock, 1992.
SEEDS Embryo with two large fleshy cotyledons, endosperm lacking. (Young & Young, 1992).
HabitatOccurring in dry to mesic well drained substrates of barrens, roadside banks, slopes, ridges and mountain balds.
DistributionIndigenous to eastern North America.
United States -- CT, DE, MA, MD, ME, NC, NH, NJ, NY, PA, RI, VA, VT, WV
Canada -- ON
New York Metropolitan Region -- Native throughout the metropolitan region.
Rarity StatusGlobal Heritage Rank -- G5
Connecticut -- Not listed
New Jersey -- Not listed
New York -- Not listed
Flowering April [week 4] - May [week 4] (June [week 3])
Fruiting July [week 4] - October [week 1] Exhibits masting (Wolgast, 1972). One study suggests that genetics plays an major role in determining acorn yields(Wolgast, 1978). One study suggests that high humidity levels at flowering time can inhibit acorn yields(Wolgast, 1977).
Dispersal Small predators of acorns facilitate dispersal by dropping undamaged nuts and failing to recover cached nuts. These include Sciurus carolinensis (gray squirrel), Sciurus niger (fox squirrel), Glaucomys volans (Southern Flying Squirrel), Tamias striatus (eastern chipmunk), Peromyscus leucopus (white-footed mouse), Peromyscus maniculatus (deer mouse),Quiscalus quiscula (common grackle) and Cyanocita cristata (blue jay). (Ivan & Swihart, 2000) (Smith, 1972) (Briggs & Smith, 1989) (Wolff, 1996) (Bosema, 1979) (Darley-Hill & Johnson, 1981) (Johnson & Webb, 1989) (Johnson, et al., 1993) (Vaughan, 1991).
In addition, one study found that many predators preferred the basal end of the acorn and consumed only 30-60% of the cotyledon. A chemical analyses of acorns from two species revealed that the concentration of protein-precipitable phenolics (primarily tannins) was 12.5% (Q. phellos) and 84.2% (Q. laevis) higher in the apical portion of the seeds where the embryo is located, suggesting that many acorn consumers consistently eat only a portion of the cotyledon of several species of acorns and thereby permit embryo survival. (Steele, et al., 1993).
Probably included in the diet of the grey fox (Urocyon cinereoargenteus) (Scott, 1955), eastern wild turkeys (Meleagris gallopavo silvestris) (Norman, 2003), and white-tailed deer (Odocoileus virginianus) (Bryant, et al., 1996).
General rules for collecting and storing acorns: 1. Collect acorns before they lose much water. 2. Ensure acorns are fully hydrated, soak in clean tap water overnight before placing them in storage. 3. Surface dry the acorns just before depositing them in storage to reduce mold growth. 4. Place acorns into cold storage as soon after collection as is possible. (Connor, 2004)