|Quercus phellos in autumn foliage|
|Subgenus:||Quercus subg. Quercus|
|Section:||Quercus sect. Lobatae|
Quercus phellos, the willow oak, is a North American species of a deciduous tree in the red oak group of oaks. It is native to the eastern and central United States from Long Island Sound south to northern Florida, and west to southernmost Illinois, Missouri, Oklahoma, and eastern Texas. It is most commonly found growing on lowland floodplains, often along streams, but rarely also in uplands with poor drainage, up to 400 meters (1,300 ft) altitude. Willow oak's natural range extends into southeastern Pennsylvania and southern New Jersey. The book Pennsylvania Trees (1928), written by state chief forester Joseph Illick, records willow oak as occurring in Lancaster, Bucks, Chester, Delaware, and Philadelphia counties, chiefly on wet sites, occasionally in drier, upland ones. Much of that area has been built over and developed since World War II, and the tree is now classified as endangered in the state.
It is a medium-sized tree growing to 20–30 metres (65–100 ft) tall (exceptionally to 39 m, 128 ft), with a trunk up to 1–1.5 m (40–60 in) diameter (exceptionally 2 metres, 6.6 ft). It is distinguished from most other oaks by its leaves, which are shaped like willow leaves, 5–12 cm (2–4 3⁄4 in) long and 1–2.5 cm (3⁄8–1 in) broad with an entire (untoothed and unlobed) margin; they are bright green above, paler beneath, usually hairless but sometimes downy beneath. The fruit is an acorn, 8–12 mm (5⁄16–15⁄32 in) long, and almost as wide as long, with a shallow cup; it is one of the most prolific producers of acorns, an important food tree for squirrels, birds, and other animals in the forest. The tree starts acorn production around 15 years of age, earlier than many oak species.
Willow oaks can grow moderately fast (height growth up to 60 cm, 2 ft a year), and tend to be conic to oblong when young, rounding out and gaining girth at maturity (i.e. more than 50 years).
Cultivation and uses
The willow oak is one of the most popular trees for horticultural planting, due to its rapid growth, hardiness, balance between axial and radial dominance, ability to withstand both sun and shade, light green leaf color and full crown. Despite being heavily used in landscaping in the Southern US (such as Washington, D.C., Charlotte, North Carolina and Atlanta, Georgia) around malls, along roads, etc., the trees tend to grow larger than planners expect, which often leads to cracked sidewalks.
Distribution and Occurrence
- "Quercus phellos". iucnredlist.org. iucnredlist. 2016. Retrieved 4 November 2017.
- "Quercus phellos". County-level distribution map from the North American Plant Atlas (NAPA). Biota of North America Program (BONAP). 2014.
- Nixon, Kevin C. (1997). "Quercus phellos". In Flora of North America Editorial Committee (ed.). Flora of North America North of Mexico (FNA). 3. New York and Oxford – via eFloras.org, Missouri Botanical Garden, St. Louis, MO & Harvard University Herbaria, Cambridge, MA.
- "Quercus phellos". fs.fed.us. p. 1. Retrieved 21 July 2019.
- Schlaegel, Bryce E. (1990). "Quercus phellos". In Burns, Russell M.; Honkala, Barbara H. (eds.). Hardwoods. Silvics of North America. Washington, D.C.: United States Forest Service (USFS), United States Department of Agriculture (USDA). 2 – via Southern Research Station (www.srs.fs.fed.us).