The fight to protect Martha’s Vineyard from invasive plants

The invasive culprit, Japanese stiltgrass, is easy to uproot, the most effective way to control it. — Photo by Matt Pelikan

As a land steward for The Nature Conservancy (TNC), Liz Loucks has had to cultivate a wide range of skills. (I would know: at my “real job” as a TNC ecologist and program manager, I’m her boss.) But working on the Vineyard, where the native plant life is a valuable but often vulnerable conservation target, Liz has grown especially proficient at managing vegetation: encouraging desirable native plants while getting rid of exotic competitors.

Non-native plants, of course, are all over the place, on the Island and indeed in most of the rest of the world. Some non-natives behave themselves, essentially becoming just another grass, flower, or shrub among many others. But some introduced species, usually highly adaptable ones that have evolved an effective way to disperse their seeds, can become too successful; with nothing to keep their populations in check, they dominate portions of the landscape, stifling native plant life and reducing diversity.

Biologists call such aggressive species “invasives,” and Island conservation organizations would all agree that they pose a serious threat to the ecological uniqueness of the Vineyard. Some invasive plants are so widespread that we couldn’t get rid of them if we tried: Asiatic bittersweet and autumn olive, for example, must rank among the most abundant plants on the Island, virtually inescapable in developed or agricultural areas. But it’s still possible to stop new invasive species from getting established, or to prevent established invasives from gaining a foothold in the Vineyard’s most natural habitats.

So conservation land managers like Ms. Loucks often invoke a strategy called “Early Detection, Rapid Response” (EDRR) to address invasive plants. Basically, you pick your battles, staying vigilant for new arrivals, and addressing invasive plants at newly infested sites, where you still have a chance of winning, and where winning matters most.

Which brings us to a plant called Japanese stiltgrass. It’s not an unattractive plant. A vaguely bamboo-like annual, its leaves alternate along the stem and show a distinctive grayish stripe down their centers. Tolerant of a wide range of conditions, it grows best in moist soils and shady sites, such as along streams. Unfortunately, these habitats often support a high number of rare, highly specialized native species. So when stiltgrass gets out of control, it often does so in places where it overwhelms important populations of native plants.

Familiar with stiltgrass from her work in states to the south of us, where it can dominate large areas, Liz was concerned to discover a patch of this plant near TNC’s Hoft Farm preserve shortly after she moved to the Island six years ago. It probably arrived by accident, its seeds or seedlings imported along with soil, potted plants, or other landscaping products. While the location of the population was not ecologically sensitive, the plant is a master at dispersing its seeds, and Liz’s concern was that this species would inevitably spread until it did reach important habitat. It also seemed likely that this invader, which enjoys warm conditions, would grow more potent here as the climate warms over coming decades.

It was a perfect opportunity for EDRR. Liz contacted property owners for permission and began pulling all the stiltgrass she could find, trying to yank it before it could set seed. The seeds can persist for years in the soil before germinating, so the work needed annual repetition; new patches have popped up, likely from old seeds, but other patches have been thinned or eliminated.

Last Saturday, Ms. Loucks organized a volunteer workday for this year’s round of stiltgrass yanking. Concern over the impending arrival of hurricane Irene limited attendance, but I joined Liz, Edgartown seasonal resident Greg Palermo, and Kevin Irby, a TNC intern from Middlebury College, to launch a surprisingly effective assault on this plant.

A shallow-rooted plant that sprawls much like crabgrass, Japanese stiltgrass is mercifully easy to pull. I found that with a firm grip on the base of a stem and a pull of just the right strength and speed, I could remove entire plants neatly, with little soil disturbance or damage to other plants. Working quickly, the four of us filled a huge bag with what had formerly been a half-dozen patches of this undesirable plant. The grass will be left to decompose in the bag, to prevent it from starting a new infestation.

Much of Liz’s job consists of similar projects, addressing such threats as Phragmites on Edgartown Great Pond or spotted knapweed and cypress spurge on sandplain grassland. She has pounced on two newly discovered invasives on the Vineyard: a stand of kudzu, a tenacious vine that has obliterated natural habitat in large areas of the South, and the Island’s first known giant hogweed, the sap of which can cause a painful rash. (Liz tackled it with raingear on.) Her work this season was supported by a grant from the Edey foundation and assisted by volunteers and TNC’s summer intern corps.

But it’s work that never ends. While attacking the giant hogweed in West Tisbury, Liz was dismayed to find another population of Japanese stiltgrass. Time for another rapid response!