Tansy

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 (20–59 in) tall, and branching near the top. The leaves are alternate, 10–15 cm (3.9–5.9 in) 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 fern-like 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 resistance to the toxins and subsist almost exclusively on the plant.

History of Uses

Tansy has a long history of use. The first historical records of its cultivation for medicinal purposes involved the ancient Greeks. In the 8th century AD it was grown in the herb gardens of Charlemagne and by Benedictine monks of the Swiss monastery of Saint Gall. Tansy was used to treat intestinal worms, rheumatism, digestive problems, fevers, sores, and to bring out measles.

During the Middle Ages and later, high doses were used to induce abortions. On the other hand, tansy was also used to help women conceive and to prevent miscarriages. In the 15th century, Christians began serving tansy with Lenten meals to commemorate the Passover bitter herbs eaten by the Israelites. Tansy was thought to have the added Lenten benefits of controlling flatulence brought on by days of eating fish and pulses and of preventing the intestinal worms believed to be caused by eating fish during Lent.

Tansy was used as a face wash and was reported to lighten and purify the skin. In the 19th century, Irish folklore suggested that bathing in a solution of tansy and salts would cure joint pain.

Insect repellent

Tansy has also been used as insect repellent and in 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 the cemetery 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.

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

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 products containing DEET. In 2008, researchers in Sweden investigated the use of tansy to repel ticks, showing a 64–72 percent repellency for each oil constituent.

Toxicity

Many tansy species contain 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. Tanacetum annuum is often confused with common tansy (Tanacetum vulgare) but the former produces an essential oil that is completely different chemically as it contains no thujone and high amounts of chamazulene making the oil dark blue in color, giving rise to its common name of Blue Tansy Oil. Despite claims by some unethical resellers of essential oils who adulterate the very expensive Blue Tansy (Tanacetum annuum) oil with the much cheaper oil from Tanacetum vulgare, the oil from Tanacetum vulgare is never blue in color as it contains no chamazulene. For this reason a high thujone oil from Tanacetum vulgare should never be referred to as Blue Tansy oil and any such blue oil containing significant thujone is an adulterated product.

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.

1,8-Cineole is a toxin believed to defend the plant leaves against attacks by herbivores.

Ethnomedical use

For many years, tansy has been used as a medicinal herb despite its toxicity. 19th-century Irish folklore suggests bathing in a solution of tansy and salt as a cure for joint pain. A bitter tea made with tansy flowers has been used for centuries as an anthelmintic to treat parasitic worm infestations, and tansy cakes were traditionally eaten during Lent because it was believed that eating fish during Lent caused intestinal worms. Various Tanacetum species are used ethnomedically to treat migraine, neuralgia and rheumatism and as anthelmintics. Traditionally, tansy was often used for its emmenagogue effects to bring on menstruation or end an unwanted pregnancy, and pregnant women are advised to not use this herb. Research published in 2011 identified 3,5-dicaffeoylquinic acid (3,5-DCQA) and axillarin in tansy as antiviral compounds that are active against herpes simplex virus.

Companion Planting

Tansy is also used as a companion plant, especially with cucurbits like cucumbers and squash, or with roses or various berries. It is thought to repel ants, cucumber beetles, Japanese beetles, squash bugs, and some kinds of flying insects, among others.