Willow oak (Quercus phellos) is a large deciduous tree . Leaves are very narrow with a short stalk, wavy along the margins (edges) and appear very willow-like. Typically, oak leaves (like beech, another Fagaceae) retain leaves during the winter. Leaves stand out stiffly all around very slender twigs. Bark of mature trunks is relatively smooth with faint ridges. Acorns are small (1/2” long). Native to the southeastern United States, willow oak is commonly cultivated in landscaping and common in bottom lands and other wet lowlands. This tree is easily distinguished by its leaves which are very similar to certain willows (Salix). Like all Fagales many leaves are retained during the winter. The common name derives from its willow-like leaves. Its epithet refers to the somewhat corky ridges that develop on the bark of old trees (phellos is the Greek word for cork). Quercus is the Latin name for “oak”. The Latin name for acorn is ‘glans’ which is morphological similar to the tip of the mammalian penis also called a ‘glans’.
Common name: Willow Oak, Peach Oak, Pin Oak, Swamp Willow Oak
Scientific Name (family and order): Quercus phellos L. (Fagaceae, Fagales)
Species Origin: Eastern United States
New Jersey Status: USDA Native
Habit: 60 – 80’ tall; bole 2-3’ wide;
Habitat: Zones 7 – 9; moist swampy soil.
Trunk/Stem: Bark gray and relatively smooth without obvious ridges even on large mature trunks (this smooth bark contrasts with oaks from the white oak group).
Leaves: Deciduous, Simple, Alternate. Narrowly oblong, widest at the middle, 4” long x 1” wide, ending in a small, fine point, untoothed; bright green above and paler green below. Smooth on both sides (glabrous). The margins are entire and they are always unlobed and untoothed ending in a single bristle-tip at the pointed apex. Notably the leaves are very narrow, narrower than Laurel Oak. Fall color yellow to pale orange-brown. The narrow leaves stand out stiffly all around the twig.
Flowers: Monoecious. Flowers appear on old or new growth; staminate catkins pendent and clustered; its flowers comprise a 4 – 7 lobed calyx which encloses 6 stamens. The pistillate flowers are solitary or on few-to-many-flowered spikes which form in the axial of new leaves. Individual flowers consist of a 6 lobed calyx surrounding 3-celled ovary; the whole is partly covered by the involucre.
Fruits and seeds: Fruit an acorn 5/8” long, about ¼ enclosed by cup. Downy, yellow brown. Borne on short pedicle; matures in two years.