September 2022 - Willow Oak

Common Name:  Willow oak; other names include peach oak, water oak, swamp chestnut oak. 

Botanical Name:  Quercus phellos

Native Range:  Native in the southeast of the U.S.  Grows in the coastal plain from central New Jersey and to the south.   Found in bottomlands, floodplains and adjacent slopes, and rich uplands in USDA Hardiness Zones 5 to 9 (but its winter hardiness is questionable in Zone 5).  However, not found in the interior of the N.J.’s pine barrens as it is extremely fire intolerant.

Height: Typically grows 40 to 60 feet high but can reach 100 feet.

Spread: Crown is typically 25 to 50 feet wide.

Form:  Pyramidal in youth, its straight trunk supports an oblong-oval to rounded crown at maturity.  The tree’s long, fine-textured, narrow leaves give it a willow-like appearance.  Some consider it to be the best oak for overall texture and form.  

Growth Rate:  Has a medium growth rate, 1 to 2 feet per year.

Sun:  Full sun or part shade. 

Soil:   Slightly acid, moist and well-drained soil preferred, but can adapt to other conditions, including clays with somewhat poor drainage.  Will not tolerate calcareous soils.  In New Jersey usually found in wet or low woods bordering swamps, streams, and canals.

Leaf Description:  Alternate, simple, narrowly elliptical or lance-shaped, 2 to 5 1/2 inches long and 1/3 to 1 inch wide.  Leaf margins are slightly wavy and entire.  Leaves end in a sharp bristle tip and are attached to the stem by a petiole 1/8 to 1/4 inch long.  In spring they are a light to bright green but become darker green in summer.  

Fall Color:  Its deciduous leaves turn yellow, bronze-orange, yellow-brown and russet red in autumn.  

Flower Description:  Willow oak is monoecious; with male and female flowers on separate catkins on the same tree.   Male flowers are in slender yellow-green hairy catkins, 2 to 3 inches long borne from axils of the previous year’s growth.  Female flowers are tiny, clustered in few-flowered catkins, in the axils of the current year’s growth.  Flowering occurs around April, about a week before the leaf buds open.

Fruit:  Fruits are acorns, solitary or paired, greenish-brown, 1/2 inch or less long and wide, almost globe-shaped, and enclosed at base by a thin, saucer-like cap that is striated with alternating brown and blackish bands.  Matures in second season (in 18 months).

Bark Description:  Young stems are slender, smooth, and somewhat lustrous, reddish-brown to dark brown.  Older trees have gray-brown and slightly red-tinged and generally smooth trunk and limbs, although shallow narrow fissures form irregular plates (gray to dark gray-brown) on more mature trees. 

Wildlife Benefit:  Oaks are an important element in the food web.  They tend to have a prolific seed crop is an important food source for dozens of bird species.  They are also eaten by squirrels and numerous other mammals.  And oaks are not just a food source.  They are the larval host for at least two species of butterflies.   They offer nesting sites.  Dozens of species of arthropods, mollusks, and annelids depend on oak leaf litter for nourishment and protection.  

Tolerates:  Urban pollution, clay soil and wet soil.

Possible Disease and Insect Problems:   Considered to have good resistance to pests and to be a low-maintenance tree.  Even so, oaks can be affected by diseases imported from other continents, such as sudden oak death and oak wilt.  And occasionally by chestnut blight, shoestring root rot, anthracnose, oak leaf blister, cankers, leaf spots and powdery mildew. Potential insect pests include scale, oak skeletonizer, leaf miner, galls, oak lace bugs, borers, caterpillars and nut weevils. 

Uses:  

• A splendid avenue, street, or boulevard tree; also excellent for large area use, such as around commercial establishments and in golf courses and parks.
• Can be suitable on properties with large lawns but may grow too large for many residential settings. 
• Effective as a shade tree along ponds or in water gardens.

Where to be found on municipal property:  There are newly planted willow oak in the Mount Lucas and Jefferson Island and along Spruce Street adjacent to the Cemetery. There are mature willow oak trees plant along William Street. There is also a mature specimen in Marquand Park. 

Additional Facts:

• A member of the red oak group.
• Transplants readily because of its shallow, fibrous root system but, if planted too near, its roots may lift pavement of a driveway or sidewalk.
• Its extensive root system helps stabilize soils, sequester carbon, and manage stormwater.

References

Missouri Botanical Garden - https://www.missouribotanicalgarden.org/PlantFinder/PlantFinderDetails.aspx?kempercode=a191 

Kartesz, J.T., The Biota of North America Program (BONAP). 2015. North American Plant Atlas. (http://bonap.net/napa). Chapel Hill, N.C. http://bonap.net/MapGallery/County/Quercus%20phellos.png

Martine, Christopher, Trees of New Jersey and the Mid-Atlantic States, Forest Education Resource Center, NJ Department of Environmental Protection, 4^th Edition, 2000, p. 70.

Dirr, Michael A., Manual of Woody Landscape Plants, Their Identification, Ornamental Characteristics, Culture, Propagation and Uses, 5^th Edition, Stipes Publishing L.L.C., 1998.

Tallamy, Douglas W., The Nature of Oaks, Timber Press, 2021.

Lady Bird Johnson Wildflower Center - https://www.wildflower.org/plants/result.php?id_plant=QUPH

U.S. Department of Agriculture, Forest Service, Southern Research Station - https://www.srs.fs.usda.gov/pubs/misc/ag_654/volume_2/quercus/phellos.htm

Cullina, William, Native Trees, Shrubs, & Vines, The New England Wild Flower Society, 2002, p 208.

Sandra Chen, July 2022