Commonly known as the tansy plant (Tanacetum vulgare), this species can provide many benefits to your garden once you know how to grow and care for this perennial flower. The yellow button-like flowers are simple, yet lovely as it attracts pollinators while also being an insect repellent with a history of medicinal uses.
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You can find Tanacetum vulgare growing in the wild in many places in North America. Some areas have labeled it as a noxious weed, but once you know how to prevent it from spreading, it really is an easy-to-grow perennial plant. The derivation of the scientific name Tanacetum vulgare is interesting. Tanacetum comes from the Greek word athanasia, which means “no death” or immortal. This is because once you dry the flowers, they last for many years, and the plant can last a long time as well.
The tansy has a few negative aspects, as it’s sometimes considered an invasive weed and is potentially risky medically, but we easily overcome these small hurdles with some knowledge and care. We hope to provide plenty of information and more within this common tansy guide while inspiring you to give this beautiful plant a home in your garden.
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Quick Care Guide
All About Tansy
The tansy plant is known as the common tansy and its botanical name is Tanacetum vulgare. Other common names include tansy common, bitter buttons, cow bitter, and golden buttons. This species is native to Asia and Europe, but it now grows everywhere in North America. It was brought to North America in the 1600s for its ornamental flowers. Incidentally, since it spreads easily, it now grows in the wild and is known as a noxious weed in many areas.
The common tansy (Tanacetum vulgare), is a herbaceous perennial that prefers full sun. The average size of the tansy plant is 3 to 5 feet tall with a spread of 12 to 18 inches. It reproduces by seeds or rhizomes, which makes it an aggressive grower that can be difficult to control and can easily become invasive. In fact, in Washington state, the common tansy is a class C weed that they recommend should be controlled. However, the tansy plant (Tanacetum vulgare) is often confused with the tansy ragwort (Senecio jacobaea) species, which is a class B noxious weed in Washington state. As a result, tansy ragwort is slightly more troublesome.
The foliage grows in a clump with multiple stems that gives the tansy plant a shrub-like appearance. The stem is reddish-brown and the alternate leaves are fern-like. Bright yellow button-like flowers are arranged in a flat-topped cluster at the end of the stem. Crushing the flowers or foliage emits a distinct odor that is strong, yet smells faintly like its cousin, yarrow. The pungent odor from the flowers is the perfect insect repellent, but it will attract native beneficial insects.
Tanacetum vulgare is potentially toxic and any gardener would be wise to wear gloves when handling the plant to prevent the plant’s oils from coming in contact with the skin. Historically, tansy has medicinal qualities that made it a frequent plant to grow in the garden. It was commonly used to treat parasitic worms and could be found on any menu in Europe being used as an herb. Nowadays, it is considered a poisonous plant that can cause death if consumed in large quantities.
There are many varieties of garden flowers that are toxic, so don’t let this deter you from planting them in your garden! The common tansy grows well in containers or within garden beds that help prevent it from becoming a noxious weed in your garden. Remember to handle it with care when you come in contact with it.
On a positive note, the common tansy will repel flies and other pest-like insects while the golden yellow flower will attract parasitic wasps and pollinators such as bees, butterflies, and hummingbirds. Since the flower can bloom from July to September, it provides plenty of food for the bees. However, it is poisonous to animals too, so don’t allow your cattle or sheep to graze within a tansy flower patch.
Tansy Plant Care
The tansy is one of the easiest plants to grow in your garden. In fact, it is commonly seen growing along roadsides and it’s naturalized to less than ideal conditions. You can grow Tanacetum vulgare in a container or in the ground, depending on how much room you have. Let’s go into greater detail in the next section about the requirements of the common tansy.
Light & 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 & 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.
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.
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.
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.
Troubleshooting
Even though tansy is an easy-to-grow plant for the everyday gardener, there are a few problems that are worth mentioning. Once you know what to watch for, you can prevent your common tansy from becoming unhealthy. Let’s take a quick look at common problems that could affect the growth of your tansy.
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.
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.
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.
Frequently Asked Questions
Q: What is tansy used for?
A: Tansy is best used as an ornamental plant to attract beneficial insects to your garden, repel flies, and it is great at accumulating potassium in the soil which can benefit surrounding plants. You can even bring fresh-cut or dried flowers into your home to keep the bugs away.
Q: Are tansy flowers edible?
A: Historically, the yellow button-like flowers and fern-like leaves were used medicinally and as a culinary herb, even though they have a bitter flavor. Nevertheless, this plant contains a toxic oil that can cause convulsions, liver damage, and brain damage as well as contact dermatitis in sensitive individuals. In the United States, this compound (thujone) is not allowed in food or alcoholic beverages, although tansy itself is sometimes used in alcohol as long as it is thujone-free. If consumed in large quantities, the flowers and leaves can be toxic and as such we don’t recommend eating it.
