Common Tansy Plant Profile

Common tansy (Tanacetum vulgare) is a a weedy perennial flower that grows from rhizomatous roots. It is now considered invasive in North America, but at one time, the plant was an important medicinal and culinary herb in Europe. Given its pedigree in the European tradition, it is not surprising that tansy flowers were soon brought to the New World by American colonists and granted a position of garden prominence. From there, however, it soon naturalized into surrounding areas and is now viewed as a noxious weed over large areas of the northern U.S.

Tansy plant's common name derives from the Greek athanatos, meaning immortality, either because it is long-lived or because tansy was used for embalming going back to ancient times. In Greek mythology, Zeus was said to have made Ganymede immortal by giving the latter tansy on Mount Olympus. Now, however, Tansy has been listed by watchdog groups as one of the worst invasive plants in North America.

Tansy can be identified by its aromatic, fern-like foliage, and bright yellow button-like flowers that appear in flat-topped clusters in summer. The leaves bears a similarity to yarrow, which is also a member of the Asteraceae family of plants.

How to Grow Common Tansy

Common Tansy is a low-maintenance plant that requires very little care on the part of the gardener. Although it is considered an invasive plant, it does have its uses. When properly harvested and dried, the bright yellow button flowers produce a soft yellow dye. The plant's history as a strewing herb still bears out today as Common Tansy will repel flies and other pesky insects. Additionally, tansy flowers add potassium to soil and attract an important beneficial insect: the ladybug.

If you're considering growing tansy flowers, keep in mind that it's prohibited in Colorado, Minnesota, Montana, Wyoming, parts of Washington state, and the Alberta and British Columbia provinces in Canada. Anywhere you do grow it, make sure to clip off the spent flowers to prevent this troublesome plant from self-seeding. You can also keep your Tansy patch under control by cutting foliage and stems to the ground at the end of the season and regularly thinning by removing a portion of the new growth including roots.

Light

Tansy flowers grow best in full sun, though they can tolerate part shade.

Soil

This perennial plant prefers well-drained, fertile garden soil but tolerate almost any soil conditions.

Water

Tansy can tolerate drought and does not need regular watering.

Temperature and Humidity

Tansy flowers are winter hardy to minus-40 degrees Fahrenheit. The leaves will turn brown, curl and dry up in extreme prolonged heat.

Are Tansy Flowers Toxic?

Tansy plants contain oil that can cause contact dermatitis in certain people who are sensitive to it. Although the tansy plant has had culinary uses in the past, if consumed in large quantities, the oil can break down in the liver and digestive tract and produce toxic metabolites that can cause stomach upset.

Pruning Common Tansy

Tansy flowers grow like weeds and can be seen in certain parts of North America along roadsides and in waste places. Best methods for keeping Tansy under control include deadheading the flowers. You might even want to try drying them and dying a skein of wool. Cut the foliage and flower stems to the ground every year to keep growth in check. Tansy roots go deep so be prepared to do some heavy shovel lifting if you want to remove the plant completely. Your most effective recourse is to dig it out and throw it on your burn pile. You can also try spot spraying with a broad spectrum weed killer. Always use caution, and wear protective clothing, gloves and goggles, when using harsh chemical herbicides.

Common Tansy vs. Tansy Ragwort

Do not confuse this plant with "tansy ragwort" (Senecio jacobea), which is a different plant altogether. Tansy ragwort is a winter annual, biennial or short-lived perennial that is also considered a noxious weed.

Common Pests and Diseases

Since the heavily scented leaves of Common Tansy act as an insect repellent, the plant is not vulnerable to pests or disease. Unfortunately, unless measures are undertaken to control its spread, the plant itself could turn out to be the biggest problem.