Habitat, Spread and Impacts

Habitat

Native habitats of common tansy are sub-alpine mountain river valleys in Siberia. Most occurrences in Europe are associated with humans. This is also true of populations in North America. In Montana, common tansy was first reported in 1931 from a sawmill site on the Gallatin National Forest in Madison County. It has since been reported from gardens, along streams, rivers and lake shores, along roads and railroads, in swamps and marshes, irrigated pastures, moist valley bottoms, rangeland, dry hillsides, and vacant lots. It prefers open sites with moist soils for at least part of the growing season. All the common tansy populations surveyed in Gallatin County were growing with smooth brome (Bromus inermis).

Spread

Common tansy traveled from Europe to North America with the early settlers. It was recommended as a necessary plant for colonial herb gardens where it was reportedly cultivated in New England in 1638 and 1663. Escaping cultivation, it was considered naturalized throughout the northeast by 1785. It was reported from Iowa and Kansas by 1912, and was well documented in California by 1951.

How common tansy escapes cultivation is not completely clear. Individual common tansy plants spread short distances by creeping rhizomes to form dense clumps. Seeds disperse by the mechanical action of dried stems flicking seeds from dried flowerheads. The small, light-weight seeds may also be carried long distances on water currents. It is doubtful seeds are blown long distances unless on the snow surface over winter. Seeds can be moved in the fur of animals, soil on animal hooves and paws, and on the clothes and footwear of people. Seeds can also be moved when inflorescences become attached to vehicles or equipment, and in mud on tires. It is possible that seeds are consumed by birds and spread via droppings. Rhizomes can be spread by tillage equipment, construction equipment, and in soil. Flowerheads baled in hay will disperse seeds when the hay is moved and fed to livestock.

Impacts

Common tansy infestations reduce livestock forage. The volatile oils in the leaves of common tansy deter grazing by cattle and horses during most of the growing season and plants are generally avoided. Elk have been observed to browse common tansy, but it is generally considered to reduce wildlife habitat. Dense clumps crowd out native plants and large infestations may reduce bio-diversity particularly in riparian areas. Common tansy infestations may reduce the habitat of pollinating insects.

The essential oils from the leaves and flowers of common tansy have been the subject of a great deal of modern research. Extracts from European populations have identified 57 compounds divided into four groups; 1,8-cineole, trans-thujone, camphor, and myrtenol. There is variability in the amounts and ratios of the groups of oils produced depending on population, habitat, and time of year.

The list of biological activities of 1,8-cineole (a monoterpene cyclic ether) is long and includes allelopathy, anesthetic, antibacterial, carcinogenic, fungicide, herbicide, insectifuge, nematicide, sedative, and testosterone hydroxylase inducer, to name a few. It is a toxin produced by leaves to defend against herbivory. Possums on a diet of cineole ceased feeding when bio-available blood levels saturated pre-systemic metabolism. This suggests ungulates have a certain tolerance for this chemical regulated by metabolism. Humans and rats metabolize cineole in the liver and excrete metabolites in the urine.

Thujone is a monoterpene with a menthol-like aroma. In the nineteenth century, it was mixed in liquor (absinthe) and consumed by notable artists (and others), including Vincent Van Gogh, to increase brain activity, develop new ideas, expand imagination, cause hallucinations, and as an aphrodisiac. These effects have been proven mythic. It is a GABA receptor antagonist that allows neurons to fire more easily and cause spasms. Mice exposed to doses of 60 mg/kg experienced convulsions and death in one minute (Van Gogh reportedly experienced fits of convulsions).

Camphor is a terpene used in the manufacture of plastics, in lacquers and varnishes, in explosives and pyrotechnics, as a moth repellent, and as a preservative in pharmaceuticals and cosmetics. It relieves itching, pain, and creates the feeling of coolness when applied to the skin where it is readily absorbed. It is used as an antibacterial injection for infected root canals in dentistry. It is metabolized in the liver and eliminated in the urine. It is one of the active ingredients in Vicks VapoRub®. It is also used as a flavor enhancer in cooking, particularly in India.

Myrtenol is an oxygenated monoterpene. Although it is not classified as an insect pheromone, it does attract pine bark beetles and has been used to enhance bait in insect traps. It has also been used as a beverage preservative, a flavoring, and as a fragrance.

< Back to Ecology and Management of Common Tansy (Tanacetum vulgare L.)

Last Modified: 02/26/2008