Bur Oak

Bur oak, Quercus macrocarpa (estimated to be over 200 years old)

Another member of the white oak subgenus, bur oak can be found throughout a large portion of the Great Plains, parts of the eastern United States, and along the southern edges of Canada. While bur oak is the most common name, others include blue oak, mossy white oak, scrub oak, and mossycup oak. Compared to all other native oaks, bur oak has the largest acorns, is also one of the most drought resistant, and is also one of the most cold tolerant of the natives.

Bark of the Bur Oak.

Although bur oak is a slow growing tree, it can reach impressive sizes and live a long life. On average, a mature tree may reach up to 30 m (100 ft), but many grow beyond that with one region recording bur oaks averaging 52 m (170 ft) tall in the Ohio Valley. They also average a lifespan of 200 to 300 years, but may also easily surpass the average. They are a preferred browse for deer and rabbits, especially when young and in reach. The acorns are also a common food source for many wildlife species including squirrels and raccoons, and when at maturity, a common nesting and roosting sight for numerous bird species.

The above bur oak is estimated to be over 200 years old. It has been home to owls, carpenter ants, bee hives, and numerous other wildlife over the years. Although located in a floodplain where water can easily reach 1 m (3 ft) in depth, it has thrive and crayfish often then create homes around it. This bur oak as well as a few other old, mature ones can be found at the Heard Natural Science Museum and Wildlife Sanctuary.

Chinkapin Oak

Chinkapin oak, Quercus muehlenbergii

Chinkapin oak, part of the white oak subgenus, is also commonly called rock oak, chestnut oak, and yellow oak. The name chinkapin comes from its resemblance of the leaves of Allegheny chinquapin, a relative of American chestnut. Chinkapin oak can be found throughout most of the eastern and central portions of the United States, preferring humidity and either limestone outcrops or upland soils derived from limestone. It may grow up to 21 m (70 ft), but is rarely a predominant tree.

Bark of chinkapin oak.

Common in oak dominated forest cover, the chinkapin oak often hybridizes with other species including bur oak, white oak, gambel oak, and swamp white oak. It also often grows as a codominant with bur oak and hackberry, but is otherwise found as scattered individuals in a mixed overstory. Hummingbirds will often use oak catkins for nesting material. The acorns are commonly consumed by numerous wildlife species, and the browse is often consumed by deer. Chinkapin oak is also a nectar source for the gray hairstreak.

Black Walnut

Black Walnut, Juglans nigra

Black Walnut is a native tree that can be found throughout the eastern and central portions of the United States. It will average 30 m (100 ft) tall and matures in 150 years, but may produce a small batch of nuts by 4 to 6 years and start producing a larger batch at 20 years. They thrive best in deep, well drained neutral soil with direct sunlight. The hard nut produced contains a sweet, oily meat enjoyed by wildlife and humans. The heavy, very resistant wood itself is highly prized for furniture and has been traditionally used for gun stocks, fencing, and airplane propellers.

Bark of a black walnut tree.

Many native groups have used parts of black walnut for everything from teas, to dyes, to treating ringworm; however, it should be noted that the bark is poisonous. One specific toxin produced by black walnut is known as juglone. This toxin inhibits the growth of other plants up to 25 m (80 ft) around it by depriving sensitive plants of energy needed for photosynthesis. As black walnut is a generally intolerant tree, juglone helps to reduce possible competition. Species that do survive juglone do not necessarily thrive.

Green Ash

Green Ash, Fraxinus pennsylvanica

Green Ash, the most widely distributed of all the American ashes, is a native dioecious tree that can be found throughout most of North America. It is extremely hardy and common along plains watercourses and moist bottomlands. For that reason, it is also often called swamp ash or water ash, as well as red ash. It can reach heights of up to 21 m (70 ft) and 0.5 m (2 ft) in diameter.

The X marks on the bark are characteristic.

With a tolerance for flooded and wet soil, in addition to a fast rate of growth, green ash is often used for city street tree planting pits. The fruit, called samara, are one seed with light colored wings. They are consumed by mammals and birds alike, and the twigs and foliage are common deer browse. The wood is used for furniture as well as athletic equipment. One of the main issues green ash, and other ash trees, face is the threat of the emerald ash borer, accidentally introduced from Asia in 2002.  While still mostly confined to the northeast and upper Midwest, the emerald ash borer is spreading.

White Mulberry

White (Fruitless) Mulberry, Morus alba

White mulberry, while native to China, was introduced to North America during the seventeenth century. It was purposely propagated to promote a North American silk industry as the primary diet of silkworms are the leaves of white mulberry. While an American silk industry never flourished, white mulberry did. It can now be found throughout a vast portion of North America, often hybridizing with native mulberry species. In some areas, white mulberry is considered invasive.

Thin, flaky bark with orange visible in some ridges.

While able to grow in the shade of other trees, in ample conditions white mulberry may reach heights up to 15 m (50 ft). The species is most often dioecious, and the fruitless mulberry is the male of any variety of species, but is most commonly white mulberry. Both native mulberry species and white mulberry produce edible fruits. The wood is commonly used for sporting goods as it is durable and flexible, and the bark may be used for dye or to create a fiber for weaving. The leaves and fruits are consumed by a variety of wildlife species including deer, hogs, and birds.

Bois d' Arc

Bois d'Arc, Maclura pomifera

The tree Maclura pomifera has a number of common names including Bois d'Arc (wood of the bow), bodark, osage-orange, hedge-apple, and horse apple tree. Historically, bois d'arc was only found in parts of Oklahoma, Texas, and Arkansas in the Blackland Prairies, Post Oak Savannas, and Chiso Mountains of Texas. The range expanded to most states and Canada with help from Prairie Farmer. Bois d'arc was proposed as perfect for hedges as it was "horse high, bull strong, and pig tight" and, until the invention of barbed wire, it made fencing entire farms possible. While not as often used for hedging now, the wood is still used for fence posts as it is a very hard wood and unusually resistant to decay. The resistance to decay and other aspects has also recently made bois d'arc and the various compounds within it of interest for medicine.

Characteristic orange bark of osage-orange.

Bois d'arc has many characteristic features including the orange bark, thorns, drooping branches, and the large, green fruits. A number of birds shelter within the branches, and squirrels will sometimes gnaw on the fruit. Unlike many trees, bois d'arc is dioecious with male and female flowers on different plants where the fruit grows on the female tree. The fruit, most often found rotting underneath the tree, is thought to be an anachronism: important in the past, but not in the present. Before the extinction of giant sloths over 13,000 years ago, the horse-apple is thought to have been a preferred food. Few others creatures could reach high past the thorns to consume such a large fruit, and none readily consume the fruit today. Giant sloths no longer exist and propagation mainly relies on humans as bois d'arc is still stuck in the past.

Sugar Hackberry

Sugar Hackberry, Celtis laevigata

The native tree Sugar Hackberry has a number of other common names including Texas sugarberry, palo blanco, and sugarberry. While a fast growing, shade and soil tolerant tree often reaching a height of 24 to 30 m (80 to 100 ft), the weak, soft wood, thin bark, and shallow roots contributes to sugar hackberry being a shorter-lived species averaging 150 years. One of the main causes of damage to sugar hackberry is from parasitic mistletoe; however, the wood of sugar hackberry is still used for furniture, flooring, and fencing. In the event of a fire, sugar hackberry will resprout from the root collar.

Canopy and trunk of Sugar Hackberry

Although now more often used for ornamental purposes, sugar hackberry is vastly important to wildlife, and was extremely important to Native Americans and early settlers. For wildlife, the sugar hackberry is a host of a few species of butterflies, provide browse for deer, and a food source for a variety of other mammals and songbirds; raccoons are especially fond of the berries from sugar hackberry. The fruit of the tree was also often consumed by Native American tribes and early settlers, either as a pulp, raw, or roasted. The bark was used to treat sore throats and the leaves and branches used to make brown and red dyes.

This month I'm doing a tour of bark found in North Texas (which includes natives and non-natives). If you would like to try identifying the bark beforehand, I'll be posting the photos first on Google+ each Monday and Wednesday for anyone and everyone to guess.

Southern Prickly Ash

(Left) Southern Prickly Ash, Zanthoxylum clava-herculis

Southern Prickly Ash grows along streams from Texas up through southern Virginia. It is taller than the Northern, or Common, Prickly Ash, Zanthoxylum americanum, reaching heights close to 14 m (45 ft) instead of the 8 m (25 ft) of its relative. Leaves range from 5 to 17 leaflets and small, green flowers appear during the early summer; however, the most characteristic feature is the sharp spines on the bark.

Also called Toothache Tree, Tingle Tongue, Hercules' club, and Pepperwood

Another common name for southern prickly ash is toothache tree due to the numbing effects of its bark, and its most frequent medicinal use among the Native Americans. This anesthetic property is the elicited by hydroxy-α-sanshool which activates a variety of sensory receptors including mechanoreceptors and nociceptors. It also inhibits anesthetic-sensitive potassium channel sub-types. Sichuan pepper also elicits a similar response as it is a spice derived from two plants of the same Zanthoxylum genus; however, it should be noted that this is a plant defensive mechanism. Just as the spines offer a mechanical defense, the chemicals within the bark offer a chemical defense from harm.


This month I'm doing a tour of bark found in North Texas (which includes natives and non-natives). If you would like to try identifying the bark beforehand, I'll be posting the photos first on Google+ each Monday and Wednesday for anyone and everyone to guess.