Knobby bark distinguishes sugarberry tree

During my first semester in college, a few years back, I had a class every Saturday at 8 a.m. Fortunately, I think, we don't have things scheduled that way now. But it was my botany lab, which I enjoyed very much. Plus, we sometimes went on class field trips.

On one of these trips we wandered over to the old quad ("The Horseshoe") here at USC, and studied this tree species —  sugarberry, hackberry, Celtis laevigata. It was pointed out by my lab instructor as looking as though someone had taken a machine-gun to the trunk. And this is the way the bark is supposed to look on a large individual.

This is a native Southeastern species, commonly attaining an eventual height of 50 or so feet, thus what they like to call a "medium" sized tree. Its wood is pale and fine-grained, but it is not valued much for timber.

Traditionally, botanists have for a long time considered it a member of the elm family, but recent research, somewhat provocatively, indicates that it is related to hops (Humulus) and marijuana (Cannabis) and belongs in the family Cannabaceae. Being a tree, it does resemble an elm, and it does have elm-like leaves, with blades that are somewhat lopsided, or unequal, at the base.

In the autumn, the leaves turn bright yellow, something like the hue you might see in various hickories, and of course, by the end of the winter they all eventually fall off.  This species occurs naturally throughout much of the South, from southeastern Virginia well into Texas, and up into the Mississippi and Ohio River valleys. It's a tree of lowlands, though, most commonly on damp soils of bottomland floodplains, so you don't see it at high elevations.

Its leaves are bright green in the summer and tear-shaped, sharply pointed, and the margins usually have at least a few jagged teeth. The flowers are tiny and unattractive. After blooming (in mid-spring), green, spherical fruits develop, on short, slender stalks.

Each fruit is a drupe, containing a single hard seed which is surrounded by a layer of soft flesh. The skin of the fruit turns a sort of dull orange, and then perhaps a bit purplish. When ripe, the fruits are edible, and they are indeed a bit sweet, tasting something like a raisin, or maybe a date. Birds love them.

But it's the bark that really makes this tree distinctive: nothing else growing in the South has this sort of rough, warty growth, a series of knob-like projections scattered over much of the otherwise smoothish surface.

Other than this bark, most everything else about this tree is rather unremarkable, and for this reason, it is often misidentified as something else. There are several species to which our Mystery Plant is related, all in the same genus, and they are not always easy to tell apart. 

This is a quick grower, relatively drought-resistant, and an excellent shade tree for yards and streets. Its bark is unusual and attractive, and it provides plenty of food for the birds. It would make a great addition to your yard or neighborhood. Or your college campus. 

John Nelson is the curator of the A. C. Moore Herbarium at the University of South Carolina, in the Department of Biological Sciences, Columbia SC 29208. As a public service, the Herbarium offers free plant identifications. For more information, visit www.herbarium.org or call 803-777-8196, or email nelson@sc.edu.