A Plague of Locusts

posted in: Local Conservation | 0

…but not the kind you’d think!

Regular readers may recall our project from earlier this year to improve nesting and foraging habitat for wood turtles at one of our regular field sites along Nashoba Brook in Acton, MA. The first-pass mowing and scarification were a great start, but as any gardener or ecologist can tell you, managing plant communities is a task that never really ends. Our team and a crew of volunteers from the town of Acton and a local Scout troop returned to the site just last week to do some additional work removing invasive species. One invasive species in particular is well-established at this site – black locust.

Photo credit: Angelyn, Identify That Plant

Black locust (Robinia psuedoacacia) is a fast-growing tree of the legume family. It boasts feathery compound leaves with oval-shaped leaflets, and each branch and twig sports wickedly sharp spines for defense (see photo at right). The plant’s status as an invasive species is somewhat complex – most of New England classifies it as such, but it occurs naturally in North America and is considered native and unproblematic as nearby as Pennsylvania. Climate change is causing black locust to spread northward with amazing speed, and as a legume, this tree fixes nitrogen into the soil wherever it becomes established. This changes the existing plant communities, and makes the habitat less hospitable for scrub and barrens-loving species that compete best where the soil is poor. In other words, if we want to preserve a relatively open meadow with low shrubs, wildflowers, and grasses, ideal foraging,  and nesting habitat for wood turtles, the locust has to go. 

Of course, like any plague of locusts, dealing with this tenacious invader is easier said than done. As mentioned before, black locusts sports stout, sharp thorns all along their branches and stems, even when young. Pulling the plants up requires a careful grip and sturdy gloves. Even if you manage to pull the sprout, the plant often spreads by sending out runners, and the root that created that sprout can be buried a foot deep and be as thick as your forearm. Black locust wood used to be prized for fenceposts and other outdoor constructions because it is heavy, dense, and rot-resistant. As you can imagine, these same qualities make its root systems very hard to dislodge. If you’re having trouble believing it, check out some of the photos from our work day below. 

A tall white man with black hair and sunglasses holds a ten-foot long curved section of root system up in front of the camera. Tools like shovels, loppers, and buckets are around his feet.
ZNE Field Technician Ryan holds up a small section of a massive black locust root network that we dislodged with shovels and picks over the course of several hours.
A blond woman in checked flannel wearing work gloves holds a twisted bundle of roots and sprouts, preparing to drop them onto a tarp covered with the stems and trunks of already-pulled locust sprouts.
ZNE Research Associate Cara adds a stubborn node of roots and suckers to the brush pile of uprooted black locust before going back to work on the next plant.

For all the arduous work, the payoff is well worth it. Working together, our team of staff and volunteers cleared out tarp-load after tarp-load of black locust, as well as other invasive plants like bush honeysuckle and multiflora rose. By the end of the day, the difference was clear: a large area now dominated by native grasses, wildflowers and shrubs , rather than by invasive woody plants that would shade out the diversity we hope to foster in the future. 

A field of blooming wildflowers and green shrubs, free of black locust, with an orange work fence and treeline in the background.
A section of the restored habitat, now free of encroaching black locust and ready to be re-planted with native shrubs in the spots the locust left behind.