FARM SCIENCE REVIEW: Landowners can offer roadblocks to invasive plants’ spread


LONDON, Ohio – There’s a chance you’ve got honeysuckle or autumn olive bushes growing on your property.
And there’s an even greater chance you or someone you know planted them.
Those bushes are just two of the common trees and shrubs growing across the state now labeled invasive, according to Scott Costello, a forester with the Ohio Division of Forestry.
Common. Costello said last week at the Farm Science Review the most common – and problematic – invaders he sees in the Buckeye State are autumn olive, honeysuckle, multiflora rose, tree of heaven and garlic mustard.
The species are all non-native plants that came from Europe and Asia, according to Costello.
Because they didn’t originate here, they don’t have the natural biological controls to keep them from spreading, he said.
“The government supported bringing many of these here – we all know the story of multiflora rose. And the state division of forestry nursery produced autumn olive.
“What they thought was a good idea a long time ago has proved to be a nightmare,” he said.
Olive. Autumn olive and Russian olive are two species widely planted throughout Ohio, especially in strip mined areas, as a wildlife habitat.
Costello said the bushy plant has been located in every Ohio county.
The plant is identified by its small, oval, dark green leaves whose undersides are lighter green to silver.
The plant is a prolific sprouter and heavy seed producer that can’t be controlled by cutting.
“People didn’t realize how aggressive it was, how fast it would spread,” Costello said.
The best treatment is simultaneous cutting and treating with herbicide, he said. He suggests foliar spraying with glyphosate during the plant’s dormant season.
Rose. Like autumn olive, the often-cursed multiflora rose bush can also be pulled.
The bush is a problem especially in northern and eastern Ohio, Costello said, and was brought here from Japan and eastern China by conservationists as a “living fence” in the 1930s.
It can easily get a foothold in woodlots and pastures because it’s tolerant of shade.
The shrub is identified by its thorns, arching branches and dense thickets. It has compound leaves, white flowers in the spring, and small, bright red fruits in the summer.
Multiflora rose can’t be cut, Costello says, because the plant grows right back. The treatment he recommends is basal spraying with glyphosate.
Basal spraying uses an oily agent to help the chemical stick to the plant, he explained.
“Cut-and-treat is your best option, but with all those nasty thorns it’s not easy.”
Tree. The tree of heaven, Ailanthus altissima, is a devil.
It’s sometimes mistaken as a walnut or sumac tree, Costello said, but can be distinguished by the notches at the leaf base.
The tree is also recognizable by its large compound leaves and yellow-green flowers in the spring. Costello said another identifier is the rancid smell of the tree’s crushed leaves, which he described as a mix of rotten peanut butter and dog feces.
“Its smell is its biggest giveaway,” he said.
A single tree can produce 300,000 seeds per year and is a prolific root sprouter, so it’s not surprising the tree thrives in Ohio.
The tree, which can grow to be 80 feet tall, has an extensive root system, making it impossible to cut and treat.
Costello said the most successful treatment method is “hack and squirt,” using cuts around the lower trunk to deliver concentrated doses of chemical killers.
Mustard. Costello said garlic mustard is the state’s most widespread invasive plant.
The biennial herb produces small rosettes in the spring, whitish yellow flowers in the summer, and long green fruits.
When crushed, its kidney-shaped leaves emit a garlic-like odor. Leaves can stay green year-round.
The plant is aggressive in woodlots and is notorious for displacing native wildflowers, Costello said.
Young plants can be pulled, but landowners must be careful to get the entire plant, Costello warned. Seeds are viable in the soil for seven years, Costello said.
Honeysuckle. Bush honeysuckle has severely infested southwest Ohio but can be found statewide.
Costello pointed out shrub-bush honeysuckle, Diervilla lonicera, a native species to Ohio. That desirable variety can be distinguished by its solid pith and yellow-to-red flowers.
Invasive varieties include amur, morrow and tatarian.
The plant is tolerant of shade and is easily identifiable by its white-to-yellow flowers and hollow pithy stem.
“This one was planted as an ornamental, and people still plant it. I cringe every time I see it in a catalog,” Costello said.
Costello said the pesky varieties have gotten a foothold in southern Ohio to the point it prevents tree regeneration.
Its control takes a lot of work, he said. In many places it’s so thick, the cut-and-treat method has to be used to move one plant and reach the next.
Costello recommends a 20 percent glyphosate application in the late summer or mid winter.
Smaller plants can also be pulled, he said.
Costello said there is government funding available through the WHIP and EQIP programs to combat invasive plants’ spread.

Get help in identifying or treating invasive plants by contacting:


Up-to-date agriculture news in your inbox!