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Tansy (Tanacetum vulgare) is a perennial,herbaceous flowering plant of the aster family, native to temperate Europe and Asia. It has been introduced to other parts of the world and in some areas has become invasive. It is also known as Common Tansy, Bitter Buttons, Cow Bitter, Mugwort, or Golden Buttons.

Description[]

Tansy is a flowering herbaceous plant with finely divided compound leaves and yellow, button-like flowers. It has a stout, somewhat reddish, erect stem, usually smooth, 50–150 cm tall, and branching near the top. The leaves are alternate, 10–15 cm long and are pinnately lobed, divided almost to the center into about seven pairs of segments, or lobes, which are again divided into smaller lobes having saw-toothed edges, giving the leaf a somewhat fernlike appearance. The roundish, flat-topped, button-like, yellow flower heads are produced in terminal clusters from mid-to-late summer. The scent is similar to that of camphor with hints of rosemary. The leaves and flowers are toxic if consumed in large quantities; the volatile oil contains toxic compounds including thujone, which can cause convulsions and liver and brain damage. Some insects, notably the tansy beetle Chrysolina graminis, have evolved resistance to the toxins and subsist almost exclusively on the plant.

Insect repellent[]

Tansy has also been cultivated and used for its insect repellent and preservative effects. It has been used for centuries as an insect and in the worm warding type of embalming. It was packed into coffins, wrapped in funeral winding sheets, and tansy wreaths were sometimes placed on the dead. Henry Dunster, the first president of Harvard University, was buried wearing a tansy wreath in a coffin packed with tansy; when “God’s Acre” was moved in 1846 the tansy had maintained its shape and fragrance, helping to identify the president’s remains. By the 19th century, tansy was used so much at New England funerals that people began to disdain it for its morbid association with death.

During the American colonial period, meat was frequently rubbed with or packed in tansy leaves to repel insects and delay spoilage. Tansy was frequently worn at that time in shoes to prevent malaria and other fevers; it has been shown, however, that some mosquito species including Culex pipiens take nectar from tansy flowers.

Organic insecticide[]

Tansy can be used as in companion planting, and for biological pest control in organic gardens and sustainable agriculture. It is planted alongside potatoes to repel the Colorado potato beetle, with one study finding tansy reduced the beetle population by 60 to 100%.

In England tansy is placed on window sills to repel flies; sprigs are placed in bed linen to drive away pests, and it has been used as an ant repellent.

In the 1940s, distilled tansy oil mixed with fleabane, pennyroyal and diluted alcohol was a well known mosquito repellent; collectors were paid five cents a pound for tansy in full bloom. Research has found that tansy extracts do indeed repel mosquitoes, but not as effectively as chemical pesticide products containing diethyltoluamide (i.e. DEET.) In 2008, researchers in Sweden investigated the use of tansy to repel ticks, showing a 64–72% repellency for each oil constituent.

The active components of the volatile oil include 1,8-cineole, trans-thujone, camphor and myrtenol, with the quantities and proportions of each varying seasonally and from plant to plant.Tansy contains a volatile oil which can cause contact dermatitis in sensitive individuals. If taken internally, toxic metabolites are produced as the oil is broken down in the liver and digestive tract. It is highly toxic to internal parasites, and for centuries tansy tea has been prescribed by herbalists to expel worms. Tansy is an effective insecticide, and is highly toxic to arthropods. Because it contains thujone, the U.S. FDA limits the use of tansy to alcoholic beverages, and the final product must be thujone-free.

1,8-cineole is a toxin believed to defend the plant leaves against attacks by herbivores. It has many biological activities including allelopathy, anesthetic, antibacterial, carcinogenic, fungicide, herbicide, insectifuge, nematicide, sedative, testosterone hydroxylase inducer, and others.

Thujone is a GABA receptor antagonist that sensitises neurons; it is reputed to be an aphrodisiac, increasing brain activity and causing hallucinations, spasms, convulsions, and even death.

Camphor has various uses, including manufacture of plastics, lacquers and varnishes, explosives and pyrotechnics; as a moth repellent; as a preservative in pharmaceuticals and cosmetics; to relieve itching and pain by creating a cooling effect on the skin; as an injectable antibacterial for root canals in dentistry; as a food flavor enhancer; and as a medical ingredient in chest rubs.

Myrtenol has been used as an insect pheromone in insect trapping, as a beverage preservative, a flavoring and a fragrance.

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