Willow Oak, Peach Oak, Water Oak, Pin Oak, Quercus phellos
Clermont, KY. Photo by Mort Schmidt
Willow Oak (Quercus phellos) isn’t native to Ohio, but it doesn’t miss by much – its range extends to neighboring Kentucky, and it can grow quite large in Ohio, given time. Like Ohio’s Shingle Oak (Q. imbricaria), Willow Oak leaves have no lobes and look nothing like the leaves we associate with Red Oak (Q. rubra) or White Oak (Q. rubra). But remember that leaf shape is secondary in tree classification. Fruits and flowers are primary, and Willow Oaks, Shingle Oaks, and all the other oaks have acorns. Notice, by the way, that one of the common names for Willow Oak is “Pin Oak”, a name more commonly used for Q. palustris. Such is the limitation of common names.
Willow Oak Leaves
Willow Oak leaves are alternately-arranged and simple. Alternately-arranged leaves and branches are not attached to the trees in pairs, directly across from each other. And simple leaves are not necessarily inornate. Simple leaves are attached directly to permanent twigs and branches, whereas compound leaves have deciduous stems with multiple blades attached to them in more or less regular numbers. Poison Ivy, for example, is easily recognized by its compound leaves with three leaflets. Willow Oak leaves are pinnately-veined (feather-like), with a single primary vein and secondary veins attached along its length. Palmately-veined (hand-like) leaves have multiple veins attached to the base of the stem.
Willow Oak leaves are linear, i.e., long and slender, with no lobes, but sometimes lance-like (lanceolate), narrowing somewhat from stem to tip. The leaves are also entire, meaning that they have smooth margins with no teeth. But like other red oaks, the leaves have tiny bristle tips, in this case, at the end of the leaves. Generally, red oaks have pointed leaves and white oaks have rounded tips. (Remember that a pointed needle draws red blood while a round snowball is white). But some of the red oaks have no point to speak of, other than one or more tiny bristles. [Notice that I use “Red Oak” and “White Oak” to indicate particular species, Q. rubra and Q. alba, and lower-case “red oak” and “white oak” to indicate the red oak and white oak groups. More of that later]. Willow Oak’s deciduous leaves are 2.5 to 4.5 inches long and 0.4 to 0.8 inches wide, and they turn brown in fall. Willow Oak leaves could easily be mistaken for willow leaves, but oaks can be distinguished by the presence of multiple terminal buds. Like their leaves, red oak buds are pointed, and white oak buds are round, but the difference isn’t always obvious.
Flowers & Bark
Quercus phellos flowers consist of green catkins. As is typical of inconspicuous green flowers, they’re wind-pollinated. Insect-pollinated flowers more often evolve showy flowers to attract bugs or birds. The 0.3- to 0.5-inch acorns are even smaller than Ohio’s smallest native, the Pin Oak. They have a shallow cap, and like other red oaks, mature in the second year. Red oak acorns are high in tannic acid, which animals find unpalatable, so they wait until spring to sprout roots. White oak acorns are sweeter, and send out roots soon after falling to avoid being eaten. All oaks are monoecious, with male and female flowers on the same tree. The USDA Silvics Manual indicates that Willow Oak starts to produce acorns at an age of approximately 20 years, and unlike many oaks, they produce good seed crops nearly every year. According to Harriet Keeler’s Our Native Trees, Willow Oak is more prone to hybridizing than most other oaks.
pointy multiple terminal buds with the autumn leaves. Photos by Mort Schmidt.
Willow Oak bark is dark brown or gray to black, and smooth to narrowly fissured, developing into shallow furrows and plates with age.
Identification Summary
Quercus phellos has a height of approximately 50 to 80 feet at maturity, and a trunk diameter of 1 to 2.5 feet. The Ohio Champion Q. phellos, located in Hamilton County, has a height of 94 feet, a trunk diameter of 5.8 feet, and a crown width of 100 feet.
ID Summary: Narrow, willow-like leaves with multiple terminal buds and tiny acorns.
Similar Trees: Willows have similar leaves but lack multiple terminal buds, acorns, and bristles at the tips of their leaves. Several other oaks have unlobed leaves, but Willow Oak leaves are the narrowest, and Shingle Oak is the only one often seen in Ohio. The USDA Guide to Eastern Oaks is an excellent, downloadable source of information on oaks.
Willow Oak usually grows along streams, and occasionally in elevated areas with poor drainage. Willow Oak tolerates flooding, but not permanent standing water. Quercus phellos grows relatively quickly by oak standards, but is long lived. Like most trees with thin bark, it’s not fire resistant, as fire resistance isn’t a useful adaptation in wet habitats. Willow Oak grows well in clay soils, and is relatively pollution-tolerant. It prefers sunny locations, and due to its shallow roots, it transplants well, making it good for landscaping.
Willow Oak Range
Willow Oak is a southeastern tree. Lucy Braun’s The Woody Plants of Ohio does not show a range map for Willow Oak, nor does the Columbus, Ohio Street Tree Inventory list Q. phellos among its 80 most common street trees. But Quercus phellos is common in the Southeast, especially in landscape settings. Because of the combination of favorable growing conditions and the presence of extensive public spaces, I saw countless Willow Oaks during a recent visit to Washington, D.C. Go for the history, stay for the Willow Oaks!
Image from USDA Forestry Service.
Willow Oak lumber has a Janka hardness of 1,460 lbf and a density of 0.77 g/cc, according to the Wood Database, compared to the median of my list of 73 Ohio trees of 1,075 lbf and 0.64 g/cc. The lumber is difficult to season without warpage, but is stable once dry. The primary use for Quercus phellos might be ornamental, but it is also used for lumber and for paper pulp. Current uses for the lumber include cabinetry, interior trim, flooring, and furniture. The red oaks are less rot-resistant than white oaks, and are not suitable for external applications.
Human Uses
Historically, Willow Oak was used for slack cooperage – barrels used to store dry materials such as flour or nails. Tight cooperage, barrels designed to hold liquids, would be made of one of the white oaks, or some other wood that doesn’t conduct liquid. Because Willow Oak is very strong for its weight, it was also used for wagon axles and fellies – the segments making up the wheel’s outer circle. Romeyn Beck Hough’s 1907 Handbook of the Trees of the Northern States and Canada states that, “Its wood is used to some extent for lumber and shingles, but mainly for fuel and charcoal”.
According to the Native American Ethnobotany Database, the Seminole people had a number of uses for Quercus phellos, including:
- Decoction of bark applied externally for pain,
- Decoction of wood ashes on the tongue to cleanse the body,
- Acorns used as a food source,
- Wood ashes used to make lye,
- Wood used to make ball sticks.
Willow Oak is an important food source for wildlife, because it provides a consistent, heavy crop of acorns. Their small size might also be easier for smaller animals to carry, and they are widely dispersed by blue jays. Willow Oaks also provide food for butterfly and moth larvae, leaf beetles, waterfowl, woodpeckers, deer, squirrels, and various rodents.
According to the North Carolina Extension Gardener Plant Toolbox, “This tree is a high-value wildlife tree for birds and mammals. It is a host plant for the larvae of the Imperial moth (Eacles imperialis), as well as numerous butterflies, including Banded hairstreak (Satyrium calanus), Edward’s hairstreak (Satyrium edwardsii), Gray hairstreak (Strymon melinus), White-m hairstreak (Parrhasius malbum), Horace’s duskywing (Erynnis horatius), and Juvenalis duskywing (Erynnis juvenalis). It is toxic to horses”.
Willow Oak in History & Mythology
Oaks play a huge part in history and mythology. In fact, early literature often uses the term “oak” to mean simply, “tree”. One of the better known stories concerning oaks involves England’s King George III, who reigned during the American Revolution. As related by Simon Wills, in A History of Trees, In 1789, King George once jumped from his carriage, and ran to an oak tree, crying, “There he is”, The king approached the tree, removed his hat, bowed deeply, and shook a branch, believing it to be the hand of his friend, the king of Prussia. From there he carried on a lively conversation. This was one of the first incidents pointing to George’s mental illness, ending with his death in 1820. However, I must admit that King George’s tree was not a Willow Oak, or any other red oak, as red oaks are a North American phenomenon. The absence of Old World red oaks makes me stretch to tap the extensive European folklore on oaks.
An historically significant Willow Oak, growing in Prince George’s County, Maryland, was witness to the War of 1812. The tree is discussed in the U.S. National Park Service’s Witness Tree Protection Program:
“One prominent landscape element that has heretofore been largely overlooked is a large, venerable willow oak tree located near the parking lot for the Oxon Hill Farm. This tree, here identified as the War of 1812 Willow Oak, likely dates to at least the early nineteenth century. As such, it has stood as a living witness to a remarkable history, from the hardships suffered by the Debutts family during the War of 1812, to the farms of Godding Croft, and finally the evolution of Oxon Hill Farm as a living history site. Given the recent expansion of interpretative themes at the farm, this remarkable tree deserves to be recognized and celebrated as a principal element of the rich cultural landscape present at Oxon Cove Park”.
Look closely the next time you see a willow tree – it just might be a Willow Oak.
Image by Mort Schmidt.
You can also listen to my talks on Ohio Broadleaf Tree Identification on YouTube, Part 1 and Part 2.
