Tansy is an aromatic perennial easily identified by its dark green fern-like foliage with golden button-like flower clusters on stems up to 5 feet. Common tansy was an important medicinal herb in Europe and was brought to the New World by American colonists and used as an ornamental plant. Today, it is considered invasive in North America.
I. Appearance and Characteristics
Tansy (Tanacetum vulgare) is a perennial, herbaceous flowering plant in the genus Tanacetum in the aster family, native to temperate Europe and Asia. It has been introduced to other parts of the world, including North America, and in some areas has become invasive. It is also known as common tansy, bitter buttons, cow bitter, or golden buttons. The Latin word vulgare means “common”.
Tansy is a flowering herbaceous plant with finely divided compound leaves and yellow, button-like flowers. It has a stout, somewhat reddish, erect stem, usually smooth, 50–150 cm (20–59 in) tall, and branching near the top. The leaves are alternate, 10–15 cm (3.9–5.9 in) long and are pinnately lobed, divided almost to the center into about seven pairs of segments, or lobes, which are again divided into smaller lobes having saw-toothed edges, giving the leaf a somewhat fern-like appearance. The roundish, flat-topped, button-like, yellow flower heads are produced in terminal clusters from mid-to-late summer. The scent is similar to that of camphor with hints of rosemary.
The leaves and flowers are toxic if consumed in large quantities; the volatile oil contains toxic compounds including thujone, which can cause convulsions and liver and brain damage. Some insects, notably the tansy beetle Chrysolina graminis, have resistance to the toxins and subsist almost exclusively on the plant.
II. How to Grow and Care
Light and Temperature
The tansy prefers to grow in full sun but can tolerate partial shade. It’s hardy to USDA zones 4-8 and could tolerate zone 3 with some winter protection. Basically, it’s a hardy winter and summer perennial that will grow in a variety of temperatures. However, tansy does not thrive in prolonged, high heat, nor does it like extreme cold conditions.
Water and Humidity
Once your tansy has become established, it is definitely drought tolerant. This makes it the perfect choice to grow on the edges of your garden where it won’t get as much water as other plants. The best time to water is in the morning before it gets too hot. Use a garden hose to water it deeply and allow the soil to dry between waterings. You can also opt for drip irrigation or soaker hoses.
During the summer months, water it more often for the first year, but after that, it will only need a good soak once or twice a month depending on the temperature. Be careful not to overwater your tansy, or else the rhizomes won’t be able to establish themselves and could become weak. What’s nice about the common tansy is that it will survive in humid climates and dry climates as long as they aren’t extreme.
Soil
Common tansy likes well-drained soil with a pH range of 4.8-7.5. This is a fairly large range, so it means the tansy can survive in a wide variety of soils. However, it is best to test the pH of your soil to make sure it’s not too alkaline or acidic. It will tolerate poor quality soil, but for the healthiest plant, we recommend a fertile garden soil amended with compost.
Fertilizer
Tansy does not require a high amount of fertilizer. Poor soils may need a general all-purpose fertilizer applied once or twice during the growing season. When growing tansy in a container, you have more control over the quality of the soil, thus it will require less application of fertilizer. Observe how well your tansy is growing, and add fertilizer as needed. Generally, the more fertilizer you add, the more it will grow and expand. This can be seen as positive or negative depending on your reasons for having this plant in your garden.
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Pruning
Cut the plant back every spring to keep the tansy cluster full and compact. Harvest flowers throughout the season and deadhead the plant when flowers fade to prevent seeds from spreading. Dead-heading also encourages more flowers to bloom later in the season. To delay or prevent blooming and spreading, cut back the foliage clusters in late summer. The seed heads will last through the winter, so if you don’t want it to become invasive, cut the dead flowers off before the cold season.
Take care when pruning that you always wear gloves when working with tansy. It contains a naturally occurring compound called thujone that can cause contact dermatitis in those sensitive to it.
Propagation
You can start tansy seeds indoors 6-8 weeks before the last frost, or sow it directly into the soil in the fall to allow the seed to cold stratify. If you allow the common tansy flower go to seed, it will self-seed aggressively, and you won’t need to worry about having enough of these flowers in your garden, but remember it will gradually spread and could easily take over. Also, remember that it also spreads by underground rhizomes. These clusters of plants are easily divided in the fall.
Repotting
When you grow tansy in a container, it should be repotted yearly using an all-purpose potting soil with good drainage. As mentioned earlier, it can grow in poor soil, but to have the healthiest tansy, it’s best to provide an ideal growing environment.
Pests and Diseases
- Common Pests
Thankfully, tansy plants aren’t bothered by many pests. Usually, they are the ones keeping the pesky bugs away. However, aphids and spider mites can become a concern in certain areas.
Aphids are insect pests found on many plants, and the tansy isn’t immune to them either. This pest lives under the fern-like leaves of the plant and feasting on all the juices. When you have a large infestation, it can stunt the growth and cause the leaves to turn yellow and fall off. To rid your plant of these tiny bugs the natural way, you can use an insecticidal soap spray or a spray made from neem oil. For very severe infestations, consider the use of an organic pyrethrin spray.
Spider mites are an insect that feeds on the fluid within each plant cell. The only way to see the spider mite is with a magnifying glass, but to distinguish them from other mites and aphids, look for the presence of webs. They too like to make their home on the underside of the fern-like leaf and eventually the leaves develop brown and white spots. If they haven’t spread to neighboring tansy plants, you can remove the affected plant. If that’s not the case, a spray of neem oil or the use of a natural insecticidal soap will do the trick.
- Common Diseases
Leaf spot and mildew are the most common diseases of the tansy. Overall, it is a resistant plant that is healthy and vibrant, but if one of these problems affects your plant, then it is best to treat it right away.
It is easy to identify leaf spot because it’s exactly what it sounds like: small brown spots on the leaves of your plant. It is caused by fungal spores that multiply from too much moisture and/or not enough air circulating around the plants. You can treat this by pulling off the affected leaves and don’t get the leaves wet when watering. OMRI-rated liquid copper fungicides are effective.
Powdery mildew is another fungal infection that thrives in humid climates and can be exacerbated by poor air circulation. The infected leaves will display white powdery spots that will eventually cover the whole leaf and spread to other parts of the plant. When catching this early, remove affected leaves. Use a neem oil spray, sulfur, or copper fungicide for prevention and treatment.
- Growing Problems
The biggest growing problem of the common tansy (Tanacetum vulgare) is that it can take over an area and become a noxious weed if not adequately controlled. When tansy plants grow in an optimal environment, they easily crowd out their neighbors. Since their roots can grow deep, hand pulling is not the ideal way to get rid of them. As mentioned previously, it’s best to remove the seeds before they fall from the flower head.
III. Uses and Benefits
- History of uses
Tansy has a long history of use. The first historical records of its cultivation for medicinal purposes involved the ancient Greeks. In the 8th century AD it was grown in the herb gardens of Charlemagne and by Benedictine monks of the Swiss monastery of Saint Gall. Tansy was used to treat intestinal worms, rheumatism, digestive problems, fevers, sores, and to bring out measles.
During the Middle Ages and later, high doses were used to induce abortions. On the other hand, tansy was also used to help women conceive and to prevent miscarriages. In the 15th century, Christians began serving tansy with Lenten meals to commemorate the Passover bitter herbs eaten by the Israelites. Tansy was thought to have the added Lenten benefits of controlling flatulence brought on by days of eating fish and pulses and of preventing the intestinal worms believed to be caused by eating fish during Lent.
- Culinary uses
Tansy was used as a face wash and was reported to lighten and purify the skin. In the 19th century, Irish folklore suggested that bathing in a solution of tansy and salts would cure joint pain.
Tansy was formerly used as a flavouring for puddings and omelettes, but is now almost unknown, except in Cork, where it is used in a sauce to accompany drisheens. The herbalist John Gerard (c. 1545–1612) noted that tansy was well known as “pleasant in taste”, and he recommends tansy sweetmeats as “an especial thing against the gout, if every day for a certain space a reasonable quantitie thereof be eaten fasting.” In Yorkshire, tansy and caraway seeds were traditionally used in biscuits served at funerals.
During the Restoration, a “tansy” was a sweet omelette flavoured with tansy juice. In the BBC documentary “The Supersizers go … Restoration”, Allegra McEvedy described the flavour as “fruity, sharpness to it and then there’s a sort of explosion of cool heat a bit like peppermint.” However, the programme’s presenter Sue Perkins experienced tansy toxicity.
According to liquor historian A. J. Baime, in the 19th century Tennessee whiskey magnate Jack Daniel, enjoyed drinking his own whiskey with sugar and crushed tansy leaf.
In the Belgian coastal province of West-Flanders small quantities of crushed dried tansy leaf were traditionally used as culinary herb to spice up pancakes and omelettes. There tansy is colloquially known as “pancake herb”.
It can also be used as a substitute for sage.
- Ethnomedical use
For many years, tansy has been used as a medicinal herb despite its toxicity. 19th-century Irish folklore suggests bathing in a solution of tansy and salt as a cure for joint pain. A bitter tea made with tansy flowers has been used for centuries as an anthelmintic to treat parasitic worm infestations, and tansy cakes were traditionally eaten during Lent because it was believed that eating fish during Lent caused intestinal worms. Various Tanacetum species are used ethno medically to treat migraine, neuralgia and rheumatism and as anthelmintics. Traditionally, tansy was often used for its emmenagogue effects to bring on menstruation or end an unwanted pregnancy, and pregnant women are advised to not use this herb. Research published in 2011 identified 3,5-dicaffeoylquinic acid (3,5-DCQA) and axillarin in tansy as antiviral compounds that are active against herpes simplex virus.
The Cherokee use an infusion of the plant for backache, use the plant as a tonic, and wear it around the waist and in shoes to prevent miscarriages. The Cheyenne use an infusion of the pulverized leaves and blossoms for dizziness and weakness.
- Other uses
Some traditional dyers use tansy to produce a golden-yellow color. The yellow flowers are dried for use in floral arrangements.
Tansy is also used as a companion plant, especially with cucurbits like cucumbers and squash, or with roses or various berries. It is thought to repel ants, cucumber beetles, Japanese beetles, squash bugs, and some kinds of flying insects, among others.
Dried tansy is used by some beekeepers as fuel in a bee smoker.
IV. How to Get Rid of Common Tansy
Individual plants or small patches of common tansy can be removed manually but they require a shovel since the roots are deep. It is also crucial to remove all of the roots, as the plant will regrow from root fragments. Make sure to wear gloves when touching the plants, as the leaves can cause contact dermatitis.
A broad-spectrum herbicide should only be used if the infestation is so large that it cannot be managed by manual removal. When using chemical herbicides. target the plants to be removed, avoid drifting, and wear protective clothing, gloves, and goggles. Mowing an infestation can be an effective way of weakening the plants before applying herbicide to the regrowth. It also requires less herbicide than when treating full-sized plants.
V. How to Prevent Common Tansy from Spreading
Whichever removal method you use, get rid of the plants before they set seed, either before or during the flowering period in the summer. If you remove common tansy in the late summer or fall after the seed heads have already developed, new plants will germinate the next year.
Find Where to Buy the Best Tansy (Tanacetum vulgare)
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