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 button-like flowers that appear in flat-topped clusters in summer. The plant bears a similarity to yarrow, which is also a member of the Asteraceae family of plants.
|Botanical Name||Tanacetum vulgare|
|Common Names||Common tansy, bitter buttons, cow bitter, golden buttons|
|Plant Type||Herbaceous perennial flowering plant|
|Mature Size||2 to 4 feet tall, 12- to 18-inch spread|
|Sun Exposure||Full sun to part shade|
|Soil Type||Well-drained, fertile soil|
|Soil pH||4.8 to 7.5|
|Bloom Time||July and August|
|Hardiness Zones||3 to 9 (USDA)|
|Native Area||Temperate regions of Europe and Asia, naturalized over much of North America|
How to Grow Common Tansy
Common tansy is an invasive plant, so growing it is not recommended. However, if there's a reason to grow the plant, you're in luck—tansy is a low-maintenance plant that requires very little care on the part of the gardener. Additionally, tansy flowers are a natural repellent against harmful insects and add potassium to soil. They also 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.
Tansy flowers grow best in full sun, though they can tolerate part shade.
This perennial plant prefers well-drained, fertile garden soil but tolerate almost ny soil conditions.
Tansy can tolerate drought and does not need regular watering.
Temperature and Humidity
Tansy flowers are winter hardy to minus-40 degrees Fahrenheit. It does not do well in extreme prolonged heat.
Toxicity of Tansy Flowers
Tansy plants contain oil that causes contact dermatitis in certain people who are sensitive to it. Although the tansy plant has had culinary uses in the past, the oil also breaks down in the liver and digestive tract and produces toxic metabolites.
Pruning Common Tansy
Tansy flowers grow like weeds (and are considered such) along roadsides in many areas of North America, so if you are curious enough to desire a look at the plant, some of you may easily be able to do so. If this invasive grows in your own landscape, at least deadhead the flowers to keep them from going to seed.
By late summer, you might wish to cut tansy to the ground, as the appearance of its fern-like foliage may start to suffer from the heat. If you cut it back early enough, a new batch of foliage will emerge in autumn (in warm climates, re-blooming may actually result).
Compared with 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
Unfortunately, there are few pests and diseases to keep common tansy from spreading rampantly. The principle problem is removing the plant when it is unwanted.
Recommended removal methods involve pulling out the plants with roots attached when soil is wet. Spot spraying with broad-spectrum herbicides can kill remaining plants. In pastures and meadows, planting competing native plants, combined with hand-pulling individual tansy plants, can gradually eliminate infestations.