Difference Between Cottonwood Bark & Black Locust Bark
Widely introduced and frequently invasive, black locusts are native to the central and southeastern U.S. but are now found across much of North America and parts of Eurasia. Cottonwoods are members of the poplar genus. In North America, they constitute some of the largest hardwoods, and frequently grow in riparian areas, including in gallery forests striking through rolling steppe. Bark is one means of trying to distinguish these unrelated broad-leaved trees. Does this Spark an idea?
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Color and Texture
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Mature black locust trees typically have trunks colored deep gray. The bark may even look black under certain lighting conditions. Many cottonwoods show similar color tendencies: They generally appear ashen gray as large adults. Both black locusts and most cottonwoods have deeply furrowed bark. Swamp cottonwood, native to bottomlands of the southern and eastern U.S., shows more variation: It may have a rufous-hued trunk with husky or woolly-looking bark. Young cottonwoods sport much smoother and lighter bark than mature specimens, often showing blotches and banding that make them somewhat resemble birches.
Size
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While usually medium-sized trees, black locusts can approach 100 feet in height. Trunks of big black locusts may be 4 feet across, but the biggest cottonwood species exceed this size. Eastern cottonwoods commonly grow taller than 100 feet and boast 6-foot trunks. Largest of all is the black cottonwood of the Pacific Northwest: This giant sometimes stands 200 feet tall with a trunk 7 feet in diameter.
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Twigs and Branches
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There are other prominent bark-related differences between black locusts and cottonwoods. Probably most notable are the paired thorns of the black locust, which may be half an inch long; they can be a formidable weapon, especially when a locust hedge or thicket is encountered. David Allen Sibley in "The Sibley Guide to Trees" (2009) notes that the upper branches and twigs of the black locust are twisting in profile. Cottonwoods often show dense upper canopies supported by tall, stout trunks with few low branches.
Cottonwoods
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In summer, black locusts and cottonwoods can easily be distinguished not by bark, but by foliage. Like many of its relatives in the legume family, black locust has pinnately compound leaves, sporting regimented pairs of green oval-shaped leaflets. Cottonwoods have simple leaves. Those of the eastern and Fremont cottonwoods are roughly triangular in shape with broad bases and prominent serrations. Leaves of the black and swamp cottonwoods are narrower, less bulging at the base and less dramatically tooth-edged. The narrowleaf cottonwood, as the name suggests, has slender, willow-like leaves. Black locusts often retain their long, prominent seed-pods through autumn and winter, another diagnostic characteristic.
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References
Resources
- Photo Credit Fall colors of the cottonwoods image by Jeffrey Banke from Fotolia.com
