Speakers at a daylong workshop on fighting invasive plants presented a wide variety of perspectives, including: why bother?
Are invasive plants taking over your land? These
goats are happy to help. Photo by Clay and Linda
Trainum, Autumn Olive Farm.
One option would be to wait for nature to handle it. We could wait for insects and other animals to adapt and start eating invasive plants, until a new ecosystem, with its own balance, emerges. But, so far, studies show that insects and wildlife make little use of invasive plant species, even those that have been here for decades or more. So plants like kudzu and tree-of-heaven can keep growing and growing, until diverse natural communities start to look like monocultures.
At the workshop, in Warrenton on May 21 , about 60 people gathered to learn what they can do to control invasive plants on land that they own or manage. The workshop was co-sponsored by PEC, Sacharuna Foundation, Virginia Working Landscapes, and United Plants Savers.
PEC’s Sustainable Habitat Manager, James Barnes, began the day by outlining various approaches and suggesting some practical management principles: focus on the invasive plants that can cause the biggest disruption, act early to contain a problem before it’s out of control, and work toward your larger ecological goals—what you do want to happen on the land.
To eradicate unwanted plants, speakers offered a wide range of alternatives—from pulling by hand to spraying chemicals, fromto adjusting biodynamic energy of the land to turning voracious goats out to graze.
Michael Lott, who manages the nearly 3,000-acre Crows Nest Nature Preserve in Stafford County discussed techniques for addressing priorities with limited staff on a large acreage. Hugh Courtney, a leader in biodynamics, which seeks to heal the Earth through a holistic approach, discussed the use of “pest peppers” made from the ashes of dead plants to deter further growth. John Pennington, a farmer, discussed how thoughtful grazing techniques can help to manage invasives—for example, by having cattle eat weeds that thrive in poor soils and deposit manure so the soil improves.
In the afternoon, speakers presented four specific case studies:
Photo by David Cappaert, Michigan
State University, Bugwood.org
The problem: Garlic mustard not only crowds out other plants on the forest floor. As Dr. Anne Alerding explained, it emits a toxin to kill mycorrhizae in the soil that support their growth. Sally Anderson, of the Virginia Native Plants Society, described how, in the Thompson Wildlife Management Area near Warrenton, garlic mustard could replace spring wildflowers, including the area’s notable display of large-flowering trilliums.
The solution: Each year, in early spring, a team of volunteers walks along the main wildflower trail and uproots the garlic mustard, which is easy to see because it emerges before other plants.
The payoff: The volunteers have cleared a corridor along the entire trail, so visitors can enjoy a carpet of trilliums and other native plants.
Photo by Chris Evans, River to River
The problem: When Clay Trainum moved back to his family farm after decades, he found it overrun with autumn olive, a hard-to-remove shrub that spreads quickly.
The solution: Trainum discovered that his South African Boer Bok goats love to eat Autumn Olive and other invasive plants. He started a business bringing the goats to other people’s properties to clear out unwanted plants.
The payoff: The goats devour invasive plants while fertilizing the soil, and the abundant invasives fatten the goats, which make delicious meat.
Photo by Jan Samanek, State
The problem: Tree-of-heaven, or ailanthus, spreads prodigiously and grows fast—up to 14 feet per year.
The solution: Dr. Chris Asaro, with the Virginia Department of Forestry, said that currently the only way to kill tree-of-heaven without it re-sprouting is to use herbicides. But a weevil from China that preys on the tree, and appears not to damage other plants, is being tested as a biological control. If the insect proves safe to release in the U.S, it could provide an alternative to spraying. Tree-of-heaven will also typically die off as a forest matures and becomes more shady, if people manage it to do so.
The payoff: Other trees provide better wildlife habitat and more valuable timber products.
Photo by James H. Miller, USDA
Forest Service, Bugwood.org
The problem: Fescue grass, found in most yards and hayfields, grows in a dense thatch so grassland birds, like bobwhite quail, can’t move along the ground. Due in part to loss of habitat, grassland bird populations have plummeted.
The solution: Dr. David Carr, from Blandy Experimental Farm, explained how they created a 35-acre meadow of native warm-season grasses, first by spraying the fields to kill fescue, then maintaining them with controlled burns. Burning in the spring gives the native grasses an advantage, because it consumes much of the fescue, a cool season grass that starts growing earlier in the year.
The payoff: Bobwhite quail have been nesting in the meadow every year since it was established. You can learn more about controlling invasive plants online in PEC's habitat webpage.
This article was featured in our Summer 2012 Member Newsletter, The Piedmont View