Tansy is a perennial member of the aster family, with serrated, fernlike leaves and flat bright yellow flowers that resemble buttons. Originally native to Europe and Asia, tansy is now widely grown and has a number of traditional medicinal uses, though most modern herbalists warn against its use by laymen. The active constituents are toxic in large doses, and it's difficult to judge the amount of thujone the most toxic of its elements without a chemical analysis. Its most common medicinal use was to 'bring on a stalled period', a euphemism for abortifacient. A strong tea made of tansy leaves and flowers can cause miscarriage, and there have been reports of deaths in women attempting to use the tea in this way. Tansy was used medicinally by the ancient Greeks, included in Charlemagne's personal herb garden, and cultivated throughout the middle ages as a remedy for a wide range of ailments. The volatile oil can be toxic even used externally, so care should be taken when using tansy for medicinal purposes. Despite these warnings, tansy is also used in cooking, and in small amounts adds a spicy tang to salads akin to cinnamon or nutmeg.
Tanacetin, tannic acid, a volatile oil, mainly thujone, parthenolides, waxy, resinous and protein bodies, some sugar and a coloring matter.
Leaves and flowering tops
tea, fresh leaves
Today, the medicinal properties formerly attributed to tansy have been largely discredited, although it is still in use as an effective insect repellent and can be an asset in the garden as a companion plant for cucumbers, squash, roses and some berries to help keep the plants pest-free. Modern herbalists warn against its medicinal use because all species of tansy are toxic and can cause hallucinations, spasms, convulsions, and even death in large doses.