Getting to the root of invasive plant problem

Roxie Campbell, park naturalst at Rock Bridge State Park, points out the sharp thorns growing on a Callery pear. These invasive trees result from the hybridizing of Bradford pear trees with wild pears.
Roxie Campbell, park naturalst at Rock Bridge State Park, points out the sharp thorns growing on a Callery pear. These invasive trees result from the hybridizing of Bradford pear trees with wild pears.

MONTGOMERY CITY - They're everywhere. They're destroying native ecosystems. And they're doing it under our very noses.

Invasive plants are an often-overlooked yet growing problem throughout mid-Missouri, said Roxie Campbell, park naturalist at Rock Bridge State Park. Campbell taught a class on identifying and fighting invasive plants Saturday for Graham Cave State Park.

Invasive plants are usually non-native plants - outside their native range, they're no longer exposed to the diseases, insects and animals that keep them in check back home.

"They spread aggressively, harm native ecology and make it difficult to use the land," Campbell said.

And they're a problem for everyone from hikers to farmers to town residents. In Missouri, sericea lespedeza chokes fields and grasslands; cattle farmers have told Campbell their animals hate to graze on it. Bush honeysuckle creates an impenetrable under-story in woods, blocking out light and suppressing the growth of other plants.

"Imagine you're a hunter and you're trying to hunt through a bush honeysuckle thicket," Campbell said. "You can't see through it, and even if you did fire a shot it'd just hit a branch."

Her own mother, at age 91, is fighting a battle against bush honeysuckle in her yard, Campbell said.

"More recently, I've realized Graham Cave State Park is beginning to have some invasive plants, and that concerns me," she said. "State parks are supposed to be the best examples of Missouri's ecology."

Though invasive plants may be hard to control, especially once they reach noticeable levels, it's not impossible. Campbell offered some tips for doing exactly that.

Identify

Step one is training your eyes to spot invasive plants and distinguish them from native species. Once you start noticing them, you'll realize they're everywhere.

"I tend to apologize to people when I train them on that," Campbell said. "I tell them, now your peaceful walks through the park will be marred."

There are too many invasive plants to describe; Campbell recommended moinvasives.org as a useful resource. The website includes tons of information, including several identification guides. A few to look up include:

In grasslands: Japanese stiltgrass, Johnson grass, sericea lespideza, Caucasian bluestem, crown vetch, bird vetch, cutleaf teasel, poison hemlock, mullein, elephant garlic and autumn olive.

In woodlands: autumn olive, multiflora rose, Callery pear, garlic mustard, bush honeysuckle, burning bush, privet, common buckthorn, wintercreeper and Japanese vine honeysckle.

In Fulton, autumn olive, cutleaf teasel, wintercreeper and bush honeysuckle seem to be particularly common.

Campbell suggested mapping out the locations of various invasive plants on your land to make it easier to keep track of them. She also noted invasive plants tend to show up first along the edges of streams and roadways and then spread further into woodlands.

Plan

The next step is research. Each invasive plant has different weaknesses and is susceptible to different elimination methods. Again, the Missouri Invasives website is helpful.

"For example, you can only spray wintercreeper in April, when it's growing new leaves - that's the only time it'll absorb," Campbell said.

Common control methods include:

  • Prescribed burns: Missouri's wild areas have historically burned every 3-10 years. Though a controlled burn won't kill most invasive plants' roots, it'll force them to regrow from the ground up and keep them from crowding out natives. Additionally, a burn treats many acres at a time. However, this method requires extensive training and preparation.
  • Hand-pulling: This works well with small plants, such as garlic mustard.
  • Root-docking: This involves using a tool such as a broad-bladed hoe to cut into the ground around a shrub, chopping through its roots, until it can be levered out of the ground. It works well on small bush honeysuckle. However, it's labor-intensive and disturbs the ground around each plant, potentially uprooting native plants. In an area already overrun by invasive plants, disturbing the soil could encourage their growth.
  • Cut-stump: This method requires an herbicide such as triclopyr or glyphosate (picloram washes into streams easily and the Department of Natural Resources no longer uses it, Campbell said). Cut down the invasive tree or shrub, making sure to cut all stems, and then treat the stumps with targeted application of concentrated herbicide (38-50 percent, mixed one part concentrate to three parts water). This method is highly targeted and less likely to kill neighboring plants, but labor-intensive.
  • Spot-spraying: Spray the affected area with an herbicide. This is effective and efficient, but it can harm non-target plants. It works well on bush honeysuckle, which stay green longer than native plants and can thus be treated well into November.

Campbell recommended researching proper use and safety before using any herbicide.

Also, take into account the quality of the site: Are there lots of native plants to protect, or is the land disturbed and completely overrun by invasives? That will help you determine how aggressive an approach to take, Campbell said. In a high-quality site, she'd suppress bush honeysuckle with controlled burns and cut-stumping. In a low-quality site - say an abandoned former agricultural field - she might just spray.

Prioritize less-disturbed, more-diverse areas.

Get to work

"If we are going to protect our land we're going to have to control invasive plants," Campbell said. "It is feasible."

Enlist young people to help out, if you can - Campbell said children have been a great help in controlling garlic mustard and bush honeysuckle at Rock Bridge, and they seem to enjoy doing it. But make sure to supervise closely, and don't let young people handle herbicides.

Make sure to clean off your boots and equipment after spending time in an invasive-heavy area. Equipment can carry seeds from one area to another, previously unaffected area.

Also, make sure to come back every year to check treated sites. No method is 100 percent effective, and it takes only a few survivors for an infestation to come roaring back.

Bonnie Wilson, a Waynesville native, attended the class after noticing trees around town were being overtaken by wintercreeper - a tough, tree-climbing invasive vine.

"I'm on a mission to save the trees in our park, and this class gave me lots of information to take back to our city council and park board," she said. "It's been very helpful."