The roundish, flat-topped, button-like, yellow flower heads are produced in terminal clusters from mid-to-late summer.

Some insects, notably the tansy beetle Chrysolina graminis, have resistance to the toxins and subsist almost exclusively on the plant.

[5] 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.

[7] Tansy was used to treat intestinal worms, rheumatism, digestive problems, fevers, sores, and to bring out measles.

[8][9][14] In the 15th century, Christians began serving tansy with Lenten meals to commemorate the Passover bitter herbs eaten by the Israelites.

[8][9] In the 19th century, Irish folklore suggested that bathing in a solution of tansy and salts would cure joint pain.

[7][9][14] 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.

[9][11] During the American colonial period, meat was frequently rubbed with or packed in tansy leaves to repel insects and delay spoilage.

It is highly toxic to internal parasites, and for centuries tansy tea has been prescribed by herbalists to expel worms.

Restoration", Allegra McEvedy described the flavour as "fruity, sharpness to it and then there's a sort of explosion of cool heat a bit like peppermint.

In the Belgian coastal province of West-Flanders small quantities of crushed dried tansy leaf were traditionally used as culinary herb to spice up pancakes and omelettes.

19th-century Irish folklore suggests bathing in a solution of tansy and salt as a cure for joint pain.

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.

[34] 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.