Too Much Tansy?
Updated: Oct 18
The Intervale Gateway Project
What’s up with all the orange tape!? For those of you coming and going on Walkers Mills Road there has been some new color introduced on the Intervale Gateway (AKA Gateway): blaze orange flagging tape, and a good amount of it too. For a few weeks before the dandelion took off these orange flags were clearly visible stretching across the field.
The Mahoosuc Land Trust Intervale Gateway subcommittee has recently enacted the first steps of a Habitat Management plan to attempt the control of the non-native and invasive Common Tansy (Tanacetum vulgare), and restore an old field environment on the Gateway preserve, that includes goldenrods, asters, and milkweed. These flags mark locations where, with help from the Gould Academy Outing Club, subcommittee members removed approximately 80 Common tansy plants by digging and bagging root balls. The digging method resulted in a 75% success rate in preventing regrowth of Common tansy in test plots in 2021.
Common Tansy, with nicknames like bitter buttons, garden tansy, cow bitter, and golden buttons, has a complex history in North America, and its abundance in and around Bethel is unique in the state of Maine. A simple Google search can cause some serious confusion, in that Huron tansy (Tanacetum bipinnatum huronense) is identified by Maine Natural Areas Program as a rare plant of Special Concern. Huron tansy is indeed rare and limited to a few river valleys in Aroostook County and Quebec and New Brunswick Provinces, occupying a similar niche along ice-scoured river banks as the federally-endangered Furbish’s lousewort (Pedicularis furbishiae). Also, Common ragwort (Jacobaea vulgaris) is sometimes referred to as tansy ragwort, it too is an entirely different species.
"A simple Google search can cause some serious confusion, in that Huron tansy (Tanacetum bipinnatum huronense) is identified by Maine Natural Areas Program as a rare plant of Special Concern."
Common tansy, on the other hand, is quite common in Northern America (though less so in Maine) with a certain fecundity that presents real, large-scale, and expensive challenges to farmers, ranchers, and field owners. A prolific seed producer, a single Common tansy plant can create 150,000 seeds in a single season that are easily spread by wind. Additionally Common tansy spreads rhizomatically, sending out runners. Well established plants are often found in constellations joined with nearby root balls. According to the US Department of Agriculture Common tansy is reported in all US states except Texas, Alabama, Georgia, South Carolina, and Florida, and in all Canadian provinces except Nunavut. It is more common in the North than the South, widely distributed across the Great Plains, and occurs in almost every county in New England and New York.
Common tansy has achieved this great distribution with particular help from humans, as it was cultivated for medicinal purposes beginning with the ancient Greeks and later spreading across North America as a widely utilitarian plant that traveled with European settlers. Documented uses of Common tansy include the treatment of intestinal worms, face wash, food preservative, pest repellent in buildings and bed linens, an abortive, cocktail garnish and many more. With a scent similar to camphor, the leaves and flowers in Common tansy contain thujone and are toxic if ingested in large quantities. Common tansy was once featured so prominently in New England funerals that it fell out of public favor due to its association with death and morbidity. More recently, Common tansy has been cultivated and introduced to stabilize disturbed soils at mining sites and along riverbanks. This was the case in New Hampshire and the reason for its introduction downstream along the Androscoggin and into Maine.
A prolific seed producer, a single Common tansy plant can create 150,000 seeds in a single season that are easily spread by wind. Additionally Common tansy spreads rhizomatically, sending out runners.
In and around Bethel, Common tansy is abundant and well established along the Bethel pathway, and Intervale-Gateway, including the Route 26 frontage in this vicinity; the lower field at Valentine Farm and and on two of the lower fields within the McCoy-Chapman Preserve. These areas are good examples of the invasive nature of Common tansy if left unchecked. In all of these places, with the exception of the Gateway field, the tansy is too dense to make digging practical, leaving mechanized tilling and reseeding the next best means of controlling the spread. One volunteer effort in October 2021, aimed at removing Common tansy seed heads in the lower McCoy field, an assessment has yet to be made of the effectiveness of this method.
It is for this reason that the Intervale Gateway subcommittee, with members Laurie Windsor, Jeff Martin, Paul Motts, and Barry Donahue adopted the Common Tansy Management Plan in March 2022. The plan, written by Motts, calls for a combination of digging and also mowing the areas in the Gateway field where it is impractical to dig. This regular mowing will continue through the growing season to prevent the tansy from seeding. And each of those orange flags will soon be receiving a Common milkweed (Asclepias syriaca) transplant in the coming weeks, with the goal of increasing biodiversity within the Intervale Gateway preserve and offering habitat niches in an old field environment. In the future, the management plan leaves the door open for some increased public access to the field and nearby vernal pool.
While field environments comprise a relatively small percentage of the total of MLT’s properties and easements, they account for a disproportionate amount of biodiversity on these preserves compared to the vast majority of our forested acreage. These same environments also require regular human intervention to maintain and require higher management costs per acre. Many wildlife species whose life cycles are adapted to field environments are losing habitat as more fields are developed, or frequently mowed for hay production. It is the responsibility of the Mahoosuc Land Trust to manage its properties to promote biodiversity and offer diverse habitats for native species.