Quercus alba is a tree to 25 m tall; 100 cm dbh; may live over 300 years (some recorded at over 400 years); (white oak group, subgenus Lepidobalanus); bark light gray, flaky, shallowly furrowed; deep rooted with fine root mats in upper soil, roots associated with ectomycorrhizal fungi (Decker and Boerner 1997); winter buds rounded, tips hairy; twigs purplish.
Leaves alternate, with 3-4 deep, rounded, pinnate lobes per side, widest above middle, base wedge-shaped, young leaves thinly hairy, mostly hairless when mature, dark, slightly blue-waxy green above, whitish below, essentially hairless; leaves expand mid-late May; winter plant leafless 164 days (Britton 1874).
Flowers monoecious, green, male flowers in catkins, female flowers 1-few; blooms May, wind pollinated.
Fruit acorns mature Oct.-Nov., shiny, thin-shelled, nut 1.5-2.5 cm long, cap deeply saucer-shaped, covering up to 1/3 of the nut, scales swollen, slightly warty-looking, kernel low in tannin, about 5.6% (Barnett 1977); matures same autumn, acorns “mast” every few years, producing very large crops, timing depends on both weather and years since last masting (Sork et al. 1993). Seeds dispersed by squirrels, probably by blue jays (Johnson and Adkisson 1985), and other animals that bury acorns. Acorns eaten by many birds and mammals that do not bury nuts (raccoon, foxes, deer, voles, mice, opossum, Muskrat, skunk) white-tailed deer, squirrels and white-footed mice are major predators of acorns. Acorn lipid content ca 5%, protein 7.8% of dry weight (Smith and Follmer 1972; Van Dersal 1940). Seeds germinate the same fall but only send down a root; nutrient storage is transferred from cotyledons to radicle. Squirrels dislike the radicle of germinated acorns (Barnett 1977). Shoot grows up the following spring.
Wetland status: FACU-.
Frequency in NYC: Common.
Habitat: Maturing or older forests from swamp forest margins to dry uplands. Apparently prefers soil pH 4.5-6.8 (USDA, NRCS 2010) found in NYC in soils with pH 4.2-5.5 (Gargiullo unpublished data), seedlings can develop in soil down to pH 3.5 (Wood 1938). Very intolerant of compaction and filling over roots. Intolerant of flooding. Moderately tolerant of drought, and shade, index 5.7. Needs at least 0.8% full sunlight to survive (compensation point) but cannot use more than 29% full sun for photosynthesis (saturation point) (Hicks and Chabot 1985).Tolerant of salt. Moderately ozone tolerant. (Hightshoe 1988).
Notes: Deer and rabbits eat seedlings and twigs, other animals eat buds (Martin et al 1951). A dominant species in pre-European forests of this region (Whitney 1994, p.78). This dominance may, in part, be due to fire use by Native Americans which favored oak species over later successional species such as sugar maple or hemlock (Ruffner and Abrams 2002). Slow growing (only chestnut oak, hickory, and beech are slower), saplings can persist in understory for decades. Young trees stump sprout if cut. Intolerant of flooding. (Sinclair et al. 1987). Quercus sp. in the white oak group are generally more drought tolerant than species in the red oak group (LeBlanc 1998). One of the most damaging pests of white oak is Goes tigrinus (Coleoptera, Lamiinae), the white oak borer. The larva of this beetle feeds in sapwood of young trees, creating a system of tunnels through the wood. This weakens the tree and leaves it open to attack by other wood borers and to fungal infections. White oak is a favored host of the Gypsy moth larvae (Lymantria dispar, Lepidoptera, Lymantriidae). Pale, flightless female moths lay eggs in masses of tan fibers on tree trunks. Larvae emerge in April and May as trees start to leaf out. New larvae disperse by spinning a strand of silk that helps them become airborne in breezes. Older larvae are blackish and hairy, with rows of red and blue dots and yellowish stripes. After about seven weeks, they may grow to over 5 cm long. Gypsy moth larvae can defoliate large areas when populations become large. A deciduous tree usually dies if defoliated more than two years in a row. Larvae pupate (often in masses) during early summer and emerge as adults in July. Male moths are dark brown and fly to find the larger females, which emit attractive sex pheromones. Several parasites and predators have been imported to control gypsy moth populations. These include the bacteria Bacillus thuringiensis, and a number of insect parasites. The fungus Entomophaga maimaiga kills larvae in wet weather and has decreased infestations. White oak foliage is also eaten by the orangestriped oakworm (Anisota senatoria, Lepidoptera, Saturniidae), white m. hairstreak butterfly, Parrhasius m-album; red banded hairstreak, Calycopis cecrops; banded hairstreak, Satyrium calanus, (Lepidoptera, Lycaenidae); Horace’s dusky wing, Erynnis horatius; Juvenal’s dusky wing, E. juvenalis; (Lepidoptera, Hesperiidae); cecropia moth, Hyalophora cecropia; luna moth, Actias luna; io moth, Automeris io; polyphemus moth, Antheraea polyphemus, (Lepidoptera, Saturniidae); imperial moth, Eacles imperialis; waxed sphinx moth Ceratomia undulosa (Lepidoptera, Sphingidae); saddleback caterpillar moth, Sibine stimulea (Lepidoptera, Limacodidae); scalloped sack-bearer moth, Lacosoma chiridota (Lepidoptera, Mimallonidae); American dagger moth, Acronicta americana (Lepidoptera, Noctuidae); fall webworm, Hyphantria cunea (Lepidoptera, Arctiidae); yellow-necked caterpillar moth, Datana ministra (Lepidoptera, Notodontidae); large tolype moth, Tolype velleda (Lepidoptera, Lasiocamidae); and other insects (Pyle 1981; Covell 1984; Tallamy, 2003). Trees are occasionally killed by outbreaks of oak anthracnose (Apiognomonia quercina, Ascomycotina). The reproductive state of this fungus is named Discula quercina. This disease causes browning and death of newly opening leaves and shoots or small decayed spots on mature leaves. However, at least under some circumstances, this fungus acts as an endophyte, which does not harm the tree and may confer some benefits upon it by infecting galls (Wilson 1995a). Trees are more susceptible during wet weather. Trees weakened by defoliation by gypsy moths or other agents, may be killed by a combined attack of the twolined chestnut borer (Agrilus bilineatus, Coleoptera, Buprestidae) and a shoestring fungus, Armilleria sp. (Basidiomycotina). A large polypore fungus, Bondarzewia berkeleyi, (Polyporus b., Basidiomycotina; Berkeley’s polypore), may occasionally be found growing on old or decayed roots near the base of white oaks or other hardwoods in late summer or autumn. Curculio weevils attack acorns, (Agrios 1980; Covell 1984; Sinclair et al. 1987; McKnight and McKnight 1987; Burns and Honkala 1990; Drooz 1985; White 1983; Johnson and Lyon 1991; Borror and White 1970; Lincoff 1981).