ASHEBORO — It all started innocently enough. Bonnie Burns, a potter in Moore County, posted a picture of a strange new plant that had cropped up among her sunflowers.
“Must have been mixed in with the seed packet,” she thought.
So, Burns posted a picture on her Facebook page and asked, “Does anybody know what this plant is?”
No one knew. Perhaps, suggested one person, it was castor bean or some other roguish plant. But then, alarms started to go off. What if it wasn’t some common native blown in on the wind? What if it was a noxious invader from another country? What if it was — gasp — hogweed?
America is no stranger to invasive plants. Some come in at the invitation of happy gardeners. Colonists in the early 1700s brought English ivy (Hedera helix). It was easy to grow and reminded them of the homeland.
Today, English ivy graces the walls of Ivy League colleges, mainly because if the groundskeepers pull it off the bricks, the mortar will come, too, causing significant structural damage. It runs rampantly through American forests and up trees of all sorts. Birds love it; environmentalists don’t.
Other invasive species come with a government stamp of approval. Southerners don’t need to be reminded that kudzu (Pueraria montana var. lobata) was once believed to be an excellent plant for soil erosion control and animal fodder. It would be, except kudzu doesn’t stop at the edge of the bank; it is meant to control and animals can’t eat it fast enough. Kudzu grows at the rate of one foot per day during the growing season and 60 feet per season.
Well-meaning government officials have brought in or promoted the use of quite a few plants like:
* Multiflora rose (Rosa multiflora). It was supposed to be a living hedge to help contain livestock. It doesn’t.
* Johnson grass (Sorghum halepens). Introduced as animal fodder, it’s toxic to cattle.
* Beach vitex (Vitex rotundifolia). Brought in for erosion control, it is a barrier to sea turtles, blocks native plant species and, of all things, may add to methane pollution.
This is matched by the amazing list of international thugs brought to the U.S. by the plant nursery industry. Blame them for Japanese honeysuckle (Lonicera japonica), Scotch broom (Cytisus scoparius) and Chinese privet (Ligustrum sinense), among others.
Invaders also come in quite by accident. Who doesn’t immediately think of the American Wild West when tumbleweeds (Salsola tragus) are mentioned? How iconic this plant has become as a symbol of the Old West; except it’s a Russian invader that is thought to have arrived in shipments of flaxseed around 1870 in South Dakota. Its original home is the Ural Mountains.
The new invasion
Most invaders are not an immediate danger to people. They crowd out native species, clog waterways and present a general nuisance. But humans fare none the worse, in any direct sense.
Some of the newest invaders aren’t so benign as Burns found out when she researched hogweed (Heracleum mantegazzianum). That’s why she reached out to experts like Taylor Williams at the N.C. Cooperative Extension Office in Moore County. Williams, in turn, contacted state experts.
Bridgette Lassiter is a weed specialist at the N.C. Department of Agriculture and Consumer Services (NCDA&CS). She oversees the invasive weed program for NCDA as the regulatory arm of the department. Her department is concerned with keeping invasive pests to a minimum in the trade.
According to information provided by Lassiter and Williams, hogweed was introduced as an ornamental from Eastern Europe. It first showed up in New York around 1917 and has since spread to moist growing sites across many of the northern tier states and Canada.
The publication states, “Giant hogweed can grow up to 15 feet tall with a taproot or fibrous root. The stems are hollow and 2-4 inches in diameter with dark reddish-purple blotches. The stem has coarse white hairs that circle the stem at the base of the leaf.
“The leaves are compound, deeply lobed, with three leaflets, up to five feet wide. The inflorescence (flower head) is an umbrella shape up to 2.5 feet in diameter. It blooms in mid to late summer. The fruits are elliptical in shape and produce up to 1,500 seeds per flower head. The seeds are viable in the soil for 15 years.”
This is the part of the research that alarmed Bonnie Burns.
“Giant hogweed can cause skin reactions when humans come into contact with its sap. The reaction, called photodermatitis, results in large, painful blisters with eruptions (worse than poison ivy) within 24-48 hours of exposure. When exposed to sunlight, the blisters leave permanent purple scars. The sap can also result in blindness if exposed to the eyes.”
Lassiter said, so far, hogweed has only been found in Watauga County. There, a homeowner introduced the plant in 2010 as a means of soil erosion control. Lassiter said she isn’t sure why the homeowner would have picked such a toxic plant. That happened before she took her current position.
She does know that NCDA has been monitoring the area since being alerted to the problem.
“We have contained it, but eight years later, we are still finding plants,” she said.
On June 13, the Isle of Wight County in Virginia posted on its government Facebook page a report about the discovery of hogweed in Berryville, Va. This was the first confirmation of the plant in Virginia. The Washington Post picked up the story and the news has spread to many other local and national media outlets.
Since then, Lassiter said, her office has received numerous calls from people worried that hogweed has crept into their backyard or into a road bank near them. Fortunately, all of the reports investigated so far have not turned up any evidence that hogweed has spread outside Watauga, she said.
“Most of what we are finding right now has turned out to be elderberry,” she said.
Although elderberry plant (Sambucus) looks nothing like hogweed, it does have an umbrella-shaped flower. That is what catches most people’s attention, Lassiter said. Lots of wild and landscape plants have white, umbrella-shaped flowers, including water hemlock, Queen Anne’s lace, cow parsnip, valerian and angelica. (For a good source that shows comparison pictures, visit https://www.dec.ny.gov/animals/72766.html.)
The end of the story
By the time Burns was able to take a sample of her plant to the local extension office it had reached over seven feet tall and had developed a flower head. The good news is Moore County officials were able to confirm her plant was giant ragweed, not giant hogweed.
Elated, Burns informed her Facebook friends, “Good news! Giant Ragweed — not as dangerous but still noxious. Relieved!”
Giant ragweed (Ambrosia trifida) is a native pest for farmers. It won’t cause skin irritation but will certainly irritate the nostrils just like its small cousin, common ragweed (Ambrosia artemisiifolia). That’s a far cry from the threat of permanent blindness.
The happy ending to this story is the compost heap — directly where Burns unceremoniously deposited her giant ragweed — before it had a chance to develop seeds and become a bully in other parts of the neighborhood.
Giant hogweed has been found in Pennsylvania, Maryland, Connecticut, Washington, D.C., Maine, Massachusetts, Wisconsin, Michigan, New York, Indiana, Illinois, Oregon, Washington and, most recently, in Virginia. It is also found in Watauga County. Barbara Lassiter, NCDA&CS extension specialist, said the plant seems to prefer growing conditions in plant zones 6 and further north. However, she is not ruling out the possibility of finding giant hogweed in the Piedmont, N.C.
Anyone who thinks they have seen giant hogweed is asked to contact her at firstname.lastname@example.org or 919-707-3749. People can also report invasive species to the NCDA&CS by calling 1-800-206-9333 or emailing email@example.com.
What you should be worried about
Not all monsters are ugly and not all invasive plants are noxious. Take purple loosestrife (Lythrum salicaria).
Purple loosestrife was a darling in the perennial plant industry just 20 or 30 years ago. Low maintenance, soft, billowing — it was a gardener’s dream.
The problem occurs when purple loosestrife gets near wetlands. Like little gremlins, if you give purple loosestrife water, it soon rages out of control.
Purple loosestrife has a thick, matted root system that defies pulling. It takes over river and stream banks, clogs irrigation canals and consumes wetlands. It reproduces vegetatively and by seed. According to one source, “Each plant can grow as many as 30 flowering stems that can produce up to 2.7 million seeds each year. The tiny seeds are easily spread by water, wind, wildlife and humans.”
Canada is using a European leaf-eating beetle in test plots to see how well the insect can control the perennial pest. Dr. Barbara Lassiter, NCDA weed specialist, is currently monitoring purple loosestrife in the Winston-Salem area and in Henderson County.
It is lovely to look at but you don’t want to let it out of your sight.
Ben Grandon, an agent with the N.C. Cooperative Extension Service in Randolph County, said local farmers are on the lookout for musk thistle (Carduus nutans) since the county was put on a quarantine list along with nine other counties, including Chatham, Rowan, Lincoln, Gaston, Cleveland, Rutherford, Polk, Buncombe and Madison.
It is native to western and central Europe. It may have come into central Pennsylvania in 1852, possibly stowing away in the soil that served as ship ballast. According to federal sources, “As of 1999, musk thistle was reported to occur in 45 states in the U.S. and all of the southern Canadian provinces”
Grandon suspects musk thistle seeds may have come to Randolph County in hay bales shipped to North Carolina in the last drought in 2007. The quarantine means farmers cannot ship hay outside the county except under certificate or permit. While the plant isn’t poisonous, cattle seem to have a real aversion to it.
Experts report cattle will not go into heavily infested fields where musk thistle is present. Besides that, the weed can quickly crowd out other fodder plants, ruining pastures for livestock. Researchers say fire doesn’t even control musk thistle. Farmers are advised to use herbicides in early spring, mow religiously and if all else fails, dig it out by hand.