No, it’s not white wisteria!
By Ken Moore
Flora Columnist
Last year, the purple wisteria draping the highway bypass around Carrboro-Chapel Hill ended its peak flowering on or about April 17. Appearing immediately afterward were grape-like clusters of white flowers hanging from trees like a late-flowering white wisteria.
As described in last week’s Flora, this spring’s flowering sequence is ahead of schedule, at least in our urban environment, where pavement and other factors provide warmer microclimates than what’s found in the cooler countryside.
Those of you who frequent the highway corridors around our town can anticipate seeing pendulous clusters of pure white flowers during the next week.
Those white flowers are the fragrant floral expression of common black locust, Robinia pseudocacia. But unlike the strangling wisteria, which is a vine, the locust is a tree. Both plants are in the bean family, and if you’ve been looking closely, you will have noticed small bean pods hanging from the bare locust branches all winter.
The original range of black locust is along the length of the Appalachians and in a large island-like area in Missouri, Arkansas and Oklahoma.
The locust’s strong wood was commonly used by Native Americans for their hunting bows. One explanation for the trees’ naturalization across our state is that this western species traveled east with the native people.
Pioneer botanist Mark Catesby observed that early settlers commonly used locust wood for the foundation support posts that stabilized their cabins. Because of its resistance to decay, locust has been so prized for fence posts and arbors that one must search far and wide these days to find a substantial source for traditional ‘locust posts.’
Though locust is not the common forest tree in the piedmont that it is in the mountains, it’s valuable here as a naturalized plant that thrives in harsh conditions on disturbed sites. Like other members of the bean family, the locust’s ‘nitrogen-fixing’ roots improve barren soils for eventual succession by a diversity of other plant species. Thickets of black locust also provide essential habitat for numerous wildlife species.
Insect pests like the locust borer keep the plant in check. Whole populations of black locust develop a ‘burned’ look about them during the summer months because of the ravenous appetites of the locust leaf minor.
Though black locust was introduced as an ornamental tree in England in the 17th century, its overabundance in parts of the European countryside is attributed to British journalist William Cobbett’s early 19th-century promotion of the locust for its fast growth and long-lasting hard wood, “superior to oak for ship and house-building.†Those uses for the locust never fulfilled Cobbett’s expectations, and this American native now runs wild across some of Europe’s countryside, looking like a white wisteria in early spring.
Email Ken Moore at flora@carrborocitizen.com.
Read more Ken Moore Citizen columns at The Annotated Flora
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