Herb to Know: Tansy

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You can grow quaint tansy in your garden easily. Just remember, it's considered toxic today, so don't ingest this herb.
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You can grow quaint tansy in your garden easily. Just remember, it's considered toxic today, so don't ingest this herb.

Common tansy (Tanacetum vulgare) is an upright perennial herb with strongly aromatic, fernlike green leaves whose aroma reminds some people of pine, others of chrysanthemum or camphor. Under favorable conditions, the plant may reach 5 feet tall, but 3 feet is more likely. From July to October, it is decked with flat clusters of 1/4 – to 1/2 -inch mustard-yellow buttons like the centers of daisies. The seed heads persist through the winter; in spring, the tiny seeds drop to the ground and soon germinate to begin a new generation. Common tansy is a native of Europe and Asia. The Puritans brought it to this country in the 17th century, and it is now naturalized throughout much of Canada and the United States.

Common tansy Tanacetum vulgare
• Family: Compositae (Asteraceae)
• Hardy perennial

Click here to see a close-up image of tansy.

Curly or fern-leaf tansy (T. v. var. crispum) is common tansy’s city cousin. Its leaves are longer, broader, more finely cut and down-curving. The plant is denser and more decorative and grows only 2 to 3 feet tall. The flowers are similar to those of the common species, but the plant may not blossom at all where summers are cool. 

Both the English name tansy and the Latin generic name Tanacetum are thought to derive from the Greek athanasia, or immortality. What does tansy have to do with immortality? There are several possible connections. The flowers are long-lasting; the leaves were used to preserve dead bodies (or at least to disguise the smell), and in Greek mythology, Ganymede, a beautiful youth carried up to Olympus by an eagle to become cupbearer of the gods, was made immortal with a drink containing tansy.  

Many people know tansy as a roadside weed, an opportunistic inhabitant of waste places, but herbalists of old considered it a valuable medicinal herb, good for just about any health problem. They recommended it for (among other ailments) worms, hysteria, kidney weakness, fevers, flatulence and gout. Externally, tansy was applied to rashes and to the swelling accompanying a sprain. In Sussex, leaves placed in the shoes were thought to cure ague. Some uses seem contradictory: It was prescribed to bring on menstruation, yet when boiled in beer and drunk or when the bruised leaves were applied to the navel, it was thought to prevent miscarriages. Small doses of the essential oil were used to treat epilepsy, but larger ones could cause seizures or death.

The essential oil is today considered toxic and potentially fatal; it contains thujone, a convulsant and narcotic. It makes sense to avoid any medicinal or culinary concoction containing tansy, especially during pregnancy. Even when used externally, tansy can irritate the skin; the AMA Handbook of Poisonous and Injurious Plants (American Medical Association Press, 1985) lists tansy in a table of plants that cause contact dermatitis.

Tansy was a common strewing herb and had a great reputation for repelling ants and moths. Cooks rubbed the leaves on meat to repel flies. This practice is not recommended today.

Growing and Harvesting

You don’t have to have a green thumb to grow tansy. Although it’s probably too coarse and scraggly for indoor growing, it grows practically anywhere outdoors, in sun or part shade, in rich loam or poor sand or clay. Although it grows best in moist, well-drained soil rich in organic matter, it grows so rampantly anyway that a poor soil might be a better choice to help keep it within bounds. Common tansy is readily propagated by divisions as well as from seed. Fern-leaf tansy needs to be propagated by divisions if it doesn’t flower where you live. Divide plants in early spring.

Tansy has been recommended as a companion plant to raspberries, fruit trees and some vegetables to control ants, aphids, squash bugs and various beetles and caterpillars. However, not only is there no scientific confirmation of any beneficial effects of this alliance, there is some evidence that when tansy is planted with brassicas, cabbageworms are more numerous, and when planted with squashes, the squash plants may be smaller.

As tansy is very attractive to aphids, its role in aphid control may be to lure them off neighboring vegetables rather than to repel them from the area. A soapy water spray will reduce the aphid population. Nematodes are another pest of tansy. Working compost or other organic matter into the soil may help make it less inviting.

Ornamental and Other Uses

Many gardeners would agree with Frances Bardswell, who wrote in The Herb Garden (first published in 1911): “We think the Tansy too much of a vagrant to be allowed a footing in the Herb garden.” Others would include tansy for its historical value or simply because they like the way it looks. It is best placed at the back of the herb bed, near a fence or wall which will help keep its tall stems from flopping over in winds and rain. 

The lush green leaves of fern-leaf tansy are equally at home in the herb garden or the perennial bed. Plants can even be pruned to make a low hedge. In the back of the border, fern-leaf tansy looks good with mugwort, valerian, fennel and dill, and contrasts pleasantly with the gray foliage of horehound. It makes a nice backdrop for shorter yellow or white flowers. For a fragrant garden, combine tansy with wormwood, blue sage and valerian.

Tansy flowers are prized for their longevity in dried arrangements. The dried leaves and flowers can be used in sachets and potpourris.

Chances are, you’ll succeed in growing tansy beyond your wildest expectations. Aside from sharing the plants with friends and neighbors (who may not appreciate your generosity), what can you do with them? Extra plants can be a potassium-rich addition to your compost pile. You can even brew up a tansy tea (a handful of leaves to a pint of boiling water) which, when cool, you can use to water your houseplants. A versatile herb indeed! 

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