Tanacetum vulgare L.

Common tansy, golden buttons, curly leaf tansy, tansy, bitter buttons

Common tansy is native to Eurasia, but widespread through­out cooler parts of North America, probably intro­duced by settlers who valued its alleged medicinal pro­perties. (The name “tansy” derives from the Greek ἀθανασία, or athanasia, meaning immortality: it was once used for embalming in hopes of achieving this.) Many plant it in gardens. In some habitats tansy is con­sidered invasive.

Plants: Plants are robust perennials reaching 6½′ (2 m) in size, though most are under 3′ (1 m). Stems grow singly or in clusters, and are coarse, grooved, and angular, branch­ing near the top. Roots are woody and often coiled.

Leaves: Leaves are alternate, very finely divided, and toothed. They smell like camphor when crushed, and are 2–12″ (5–30 cm) long. The odor is variously described as “rank” or “aromatic.” (If you crush the leaves and don’t smell this odor, there’s a good chance you have the similar-appearing Tanacetum bipinnatum subsp. huron­ense, which is endangered or threatened in some locales.)

Flowers: Flowerheads are composed of dense flat-topped clusters of 20-100 yellow disk florets, each up to ½″ (1.3 cm) around. The individual florets are often likened to buttons. Most florets resemble the center of a daisy, and lack the daisy’s “petals,” technically called ray flowers. Some tansy florets have short ray flowers though. Tansies bloom from from July to October.

Fruits: Florets produce many achenes 1/32–1/16″ (1–1.8 mm) long.

Habitats: Disturbed sites such as roadsides, river banks, out-of-use sites, and old fields, preferring bright sun.

Edibility: Poisonous Causes a rapid, weak pulse and stomach pains in lower doses, and can cause death in larger quantities. Leaves are bitter-tasting, and avoided by many (but not all) livestock. In small quantities young leaves and flowers, soaked in water, are used sparingly as a substitute for sage, to flavor dishes.

Medical: Tansy was once widely used for a variety of ail­ments, but modern herbalists generally avoid it. It contains thujone, also present in the wormwood from which the spirit absinthe is made. Thujone is a GABA_A receptor antagonist, toxic to brain, kidney, and liver cells, causing muscle spasms and convulsions in larger amounts. Thujone was once thought to stimulate cannabinoid receptors, thus causing some of the same symptoms as marijuana, but this has since been proven false.

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References:

Older scientific or horticultural names

Tanacetum vulgare description by Thomas H. Kent, not updated.

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