Stopping stiltgrass

The mission: stopping stiltgrass

By Su Clauson-Wicker | Special to The Roanoke Times
Photos by Matt Gentry | The Roanoke Times
Aug 23, 2020

NEWPORT, Va. — On a rainy Saturday morning, the New River Valley Master Naturalists took up arms against an invader of the leafy kind.

The aggressor, Japanese stiltgrass (Microstegium vimineum), is a pretty, wispy grass that chokes out native plants, destroys wildlife habitats and serves as tinder for forest fires.

The 16 volunteers pitched war on the stiltgrass, fanning out along the Woods & Field Trail at Pandapas Pond Recreation Area. They pulled and yanked, laying the uprooted grass out to dry and die or smothering it in black plastic bags. They focused on sections where the weed radiated into the forest and spots near streams.

“Nothing spreads stiltgrass faster than drainage,” said longtime Master Naturalist Suzie Leslie. “Running water distributes seeds along its course.”

A single stiltgrass plant can produce up to 1,000 seeds, explaining why 100 years after its introduction as packing material in shipments of Asian porcelain, this aggressive grass threatens 18 eastern states from New York to Florida, according to Susan Roth of Blue Ridge Partnership for Regional Invasive Species. The weed has been found as far west as the Mississippi River and in Texas.

Those seeking to eradicate stiltgrass have torched it with flame weeders, doused it in herbicide, frosted it with dry ice and released herds of hungry goats upon it (at Hawk Mountain, Pennsylvania). Still, the weed pops up in new places, carried by water or in the soil clinging to vehicle tires, animals’ feet and hikers’ shoes.

Populations of Japanese stiltgrass are widespread across the George Washington and Jefferson National Forests, particularly in disturbed soil at roadsides and forest edges, says Tom Brumbelow, botanist for U.S. Forest Service.

“Our efforts are focused upon areas where we need to protect special sites that house sensitive species and natural communities, or places where we anticipate that future soil disturbance could facilitate the spread of invasive species,” Brumbelow said.

Stiltgrass grows in several sections of Pandapas Pond, which encompasses about 500 acres of the Jefferson National Forest. New River Valley Master Naturalists regularly traipse past the stiltgrass infestations on Woods & Field Trail to reach the large pollinator garden they created and maintain.

“We’ve been seeing siltgrass for four to five years; we started pulling it up as a group this year,” said Master Naturalist Barbara Walker, who co-coordinated the workday with Sandy Weber. “We’re particularly concerned about a spot where a lovely wildflower blooms at the end of summer. It bloomed last year, and we hope it will bloom again this year. We try to weed there regularly.”

Later that morning, the citizen naturalists were happy to discover a specimen of the wildflower, grass-of-Parnassus, in bud near the stream. But the small colony of the flower that once bloomed on a bank beside the trail was gone, possibly edged out by spreading stiltgrass. Grass-of-Parnassus is listed as endangered in neighboring Maryland and Kentucky, although not in Virginia.

“Japanese stiltgrass can easily out-compete native plants on the forest floor, leading to the loss of populations of native wildflowers that support wildlife, such as pollinators, and that provide a crucial component of the visual backdrop that so many people enjoy,” said Brumbelow, the botanist. “Thick patches of Microstegium can negatively affect forest regeneration by preventing the establishment of some tree seedlings.”

In areas with a high deer population, stiltgrass easily wins the competition for survival. Deer avoid the non-native but decimate native plants, allowing stiltgrass to spread unchecked. Stiltgrass has another advantage: it releases chemicals that change the soil chemistry in a way that effectively stops other plants from growing.

The effects of stiltgrass can take a more dramatic turn in autumn. The thick patches of the drying grass create a highly flammable fuel source potentially leading to bigger and more intense wildfires.

The Master Naturalists pulling up stiltgrass work with a sense of urgency. They know that soon flowers will form low down on the stiltgrass stems hidden between stem and leaf sheaths — they can see them by peeling back the base of a leaf. At the end of August or in early September — soon — seed heads will form. At that point, it will be too late to exterminate the weed by tugging them up.

“If you try to pull stiltgrass up after the seeds form, you’re really just spreading the seeds,” Walker said. “We’re getting close to that time, but we’re not there yet.”

“Look,” exclaimed Sandy Weber, pulling up handfuls of stiltgrass, “look at all this beautiful moss hidden underneath all this stiltgrass.”

Fighting back — everyone’s responsibility

People who visit natural areas — or even their own backyards — should keep an eye out for this very invasive grass. The key identification features are a silvery stripe of hairs down the middle of the leaf’s upper surface, wiry bamboo-like stems, and long, lance-shaped asymmetrical leaves.

“To help prevent or slow the spread of invasive plants like Microstegium, make sure your boots and clothes are free from seeds before traveling from one natural area to another,” said Brumbelow. “Brushing boots off at a trailhead at the beginning and end of a hike is a good practice. Seeds can also be transported in the dirt in our car tires, so cleaning tires and wheel wells can help prevent spread as well.”

Suzie Leslie hikes with a woman who goes one step further.

“Whenever my friend goes on a hike, she carries a bundle of bags so she can carry away invasive species she sees,” Leslie said. “She’s done this week after week for years.”

Copyright 2020 The Roanoke Times