Willow Oak Quercus phellos L.

Quercus phellos on a sand dune in Brooklyn Stephen M. Young

Quercus phellos on a sand dune in Brooklyn
Stephen M. Young

Class
Dicotyledoneae (Dicots)
Family
Fagaceae (Beech Family)
State Protection
Endangered
Listed as Endangered by New York State: in imminent danger of extirpation in New York. For animals, taking, importation, transportation, or possession is prohibited, except under license or permit. For plants, removal or damage without the consent of the landowner is prohibited.
Federal Protection
Not Listed
State Conservation Status Rank
S1
Critically Imperiled in New York - Especially vulnerable to disappearing from New York due to extreme rarity or other factors; typically 5 or fewer populations or locations in New York, very few individuals, very restricted range, very few remaining acres (or miles of stream), and/or very steep declines.
Global Conservation Status Rank
G5
Secure globally - Common in the world; widespread and abundant (but may be rare in some parts of its range).

Contents

  1. Summary
  2. Conservation and Management
  3. Habitat
  4. Range
  5. Identification Comments
  6. Taxonomy
  7. Additional Resources
  8. About This Guide

Summary

Did you know?

Willow oak is also planted extensively as a street tree in New York City and it is sometimes difficult to distinguish native trees from those that were planted.

State Ranking Justification

There are five existing native populations, but except for one population of tens of trees, there are only a few trees in the other populations. There is one historical population on Long Island and one on Staten Island, but there are also many planted trees around the New York City area.

Short-term Trends

All of the existing populations are small and could be eliminated at any time since none are protected, but currently they seem stable.

Long-term Trends

This tree was always very rare in New York because of climatic conditions and the number of natural populations has remained very small over time. There are many trees in the New York City area because they have been planted as landscaping trees but are not considered natural populations.

Conservation and Management

Threats

Most populations are threatened by the development of the surrounding habitat by roadwork or residential areas. Increased fragmentation would cause more hybridization with the more abundant red oak.

Conservation Strategies and Management Practices

A natural buffer should be established around natural populations and cutting of trees should be prevented.

Research Needs

Genetic work could be done on existing natural populations to see if they are from local genetic stock or actually progeny from introduced trees.

Habitat

Habitat

In New York, Willow Oak has been found in floodplain forests, maritime grasslands, and roadside forests and woodlands (New York Natural Heritage Program 2010). Of bottomland flood plains, also on stream banks, dunes, and terraces, and, occasionally, on poorly drained uplands, from 0 to 400 meters in elevation (FNA 1997). Swamps and moist soil (Gleason & Cronquist 1991). Swamps, bottoms and other low ground, or sandy uplands (Fernald 1970).

Associated Ecological Communities

  • Floodplain forest (guide)
    A hardwood forest that occurs on mineral soils on low terraces of river floodplains and river deltas. These sites are characterized by their flood regime; low areas are annually flooded in spring, and high areas are flooded irregularly.
  • Maritime grassland (guide)
    A grassland community that occurs on rolling outwash plains of the glaciated portion of the Atlantic coastal plain, near the ocean and within the influence of offshore winds and salt spray.
  • Red maple-hardwood swamp (guide)
    A hardwood swamp that occurs in poorly drained depressions, usually on inorganic soils. Red maple is usually the most abundant canopy tree, but it can also be codominant with white, green, or black ash; white or slippery elm; yellow birch; and swamp white oak.
  • Successional maritime forest (guide)
    A successional hardwood forest that occurs in low areas near the seacoast. This forest is a variable type that develops after vegetation has burned or land cleared (such as pastureland or farm fields). The trees may be somewhat stunted and flat-topped because the canopies are pruned by salt spray. The forest may be dominated by a single species, or there may be two or three codominants.

Associated Species

  • Acer rubrum
  • Eupatorium hyssopifolium (hyssop-leaved thoroughwort)
  • Liquidambar styraciflua (sweet-gum)
  • Liriodendron tulipifera (tulip tree, tulip poplar, yellow poplar)
  • Myrica pensylvanica
  • Nyssa sylvatica (black-gum, sour-gum)
  • Parthenocissus quinquefolia (Virginia-creeper)
  • Populus
  • Prunus serotina
  • Quercus x heterophylla
  • Quercus x rudkinii
  • Rhus
  • Smilax glauca (white-leaved greenbrier)
  • Toxicodendron radicans

Range

New York State Distribution

This oak is known from a few native localities on Staten Island and Long Island except Nassau County. It is considered extirpated in Suffolk County.

Global Distribution

This is a tree of the South-Central and Southeastern United States extending north to Southern Illinois where it is rare and to Eastern Pennsylvania and Long Island where it is also rare. It does not extend south into the peninsula of Florida.

Identification Comments

General Description

Willow oak is a long-lived overstory tree, growing up to 30m tall. It has tight, gray to blackish bark. The twigs are reddish brown and glabrous, with mature buds also glabrous, ovoid, pointed, and 2 to 4 mm long. The leaves are linear to narrowly elliptic, entire except for a single bristle-tip, generally 1 to 2 centimeters wide, and glabrous or nearly so, and deciduous in autumn. The fruit (acorns) are 1 to 1.5 cm long, 1/4 to 1/2 covered by the light brown, saucer-shaped, pubescent cap (Rhoads and Block 2000, FNA 1997).

Best Life Stage for Proper Identification

Willow oak can be identified, in the appropriate season, from the seedling stage throughout its maturity.

Similar Species

Willow oak's distinct narrow, unlobed, bristle-tipped leaves are unique among New York oak species.

Best Time to See

Willow Oak may be identified whenever the leaves are out.

  • Vegetative
  • Fruiting

The time of year you would expect to find Willow Oak vegetative and fruiting in New York.

Willow Oak Images

Taxonomy

Willow Oak
Quercus phellos L.

  • Kingdom Plantae
    • Phylum Anthophyta
      • Class Dicotyledoneae (Dicots)
        • Order Fagales
          • Family Fagaceae (Beech Family)

Additional Resources

Best Identification Reference

Gleason, Henry A. and A. Cronquist. 1991. Manual of Vascular Plants of Northeastern United States and Adjacent Canada. The New York Botanical Garden, Bronx, New York. 910 pp.

Other References

Fernald, M.L. 1950. Gray's manual of botany. 8th edition. D. Van Nostrand, New York. 1632 pp.

Flora of North America Editorial Committee. 1997. Flora of North America north of Mexico. Vol. 3. Magnoliophyta: Magnoliidae and Hamamelidae. Oxford Univ. Press, New York. xxiii + 590 pp.

Holmgren, Noel. 1998. The Illustrated Companion to Gleason and Cronquist's Manual. Illustrations of the Vascular Plants of Northeastern United States and Adjacent Canada. The New York Botanical Garden, Bronx, New York.

Little, E.L., Jr. 1979. Checklist of United States trees (native and naturalized). Agriculture Handbook No. 541. U.S. Forest Service, Washington, D.C. 375 pp.

New York Natural Heritage Program. 2010. Biotics database. New York Natural Heritage Program. New York State Department of Environmental Conservation. Albany, NY.

New York Natural Heritage Program. 2023. New York Natural Heritage Program Databases. Albany, NY.

Rhoads, Ann F. and Timothy A. Block. 2005. Trees of Pennsylvania. A Complete Reference Guide. University of Pennsylvania Press, Philadelphia, PA.

Weldy, T. and D. Werier. 2010. New York flora atlas. [S.M. Landry, K.N. Campbell, and L.D. Mabe (original application development), Florida Center for Community Design and Research http://www.fccdr.usf.edu/. University of South Florida http://www.usf.edu/]. New York Flora Association http://newyork.plantatlas.usf.edu/, Albany, New York

Links

About This Guide

Information for this guide was last updated on: February 28, 2011

Please cite this page as:
New York Natural Heritage Program. 2023. Online Conservation Guide for Quercus phellos. Available from: https://guides.nynhp.org/willow-oak/. Accessed March 31, 2023.

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