Plant · P-040

Black Locust

Robinia pseudoacacia

Black Locust is a fast-growing nitrogen-fixing tree whose wood is so rot-resistant that a fence post cut from it can stand in the ground for 30 to 50 years untreated. It fixes its own nitrogen, coppices and resprouts vigorously, and its timber is the standard alternative wherever pressure-treated lumber is banned. The surprise for anyone who plants one: it spreads by root suckers into dense, thorny thickets that come up through pavement, and a few states list it as a noxious or regulated weed, so growers usually keep it in check with a grazed or mowed margin rather than let it run. Its flowers are heavily worked by honeybees and yield a honey that commands a premium price.