Herb · Asteraceae
Common Tansy
Tanacetum vulgare
A forgiving golden-flowered herb that thrives on benign neglect and forgives a beginner's slips.
Full sun
Every 7–14 days
50–86°F · 10–30°C
USDA 3–8
Overview
If you are just starting out, common tansy is a kind plant to learn on. It is a hardy perennial in the daisy family, and you will know it by the flat clusters of button-shaped golden-yellow flowers and the ferny, strongly scented leaves. Tansy first crossed over from Europe as a garden and medicinal plant, and it has settled comfortably across much of North America. Brush a leaf between your fingers and the bitter, almost camphor smell will greet you like an old friend.
Here is the reassuring part: tansy truly thrives on neglect. It takes poor soil, drought, and cold down to zone 3 in stride, and it picks up speed once it settles in. The one thing to stay ahead of is its urge to wander, because creeping rhizomes and free self-seeding let it travel farther than you planned, and several states list it as a noxious weed. Give it a spot you can keep an eye on, or set it aside if your area does not allow it, and you will both be happier for it.
One gentle caution before you plant. Every part of tansy holds thujone and sesquiterpene lactones, which make it toxic to pets, livestock, and people, so think of it as a pretty, pest-shooing herb rather than anything to cook with. Grown for looks and kept out of reach, it is an easy, giving plant to have around.
Care
The short version: give it full sun and soil that drains, water it only while it is young or during a long dry spell, and keep up with deadheading and dividing so it stays where you want it. Miss a step and tansy forgives you.
Light
Tansy is happiest in full sun, where its stems stand firm and the flowers come thick and steady. A little partial shade will not hurt it, though you can expect leggier, floppier growth and fewer of those sunny buttons, so give it the brightest spot you can.
Water
Once its roots take hold, tansy is truly drought tolerant and asks for water only through a long dry spell. Give young plants a good soak until they settle, then ease off with a clear conscience, since soggy soil troubles it far more than a dry stretch ever could.
Soil
Do not fret over your soil, because tansy shrugs off dry and poor ground even as it grows lushest where things are moist and rich. It stays relaxed about pH too, settling in anywhere from 6.0 to 8.0, so long as water can drain away freely.
Temperature
Tansy feels at ease across a broad band of temperatures, right around 50°F to 86°F (10°C to 30°C), and its tough roots sleep through winters as cold as zone 3. Once it has settled, neither a hot afternoon nor a hard freeze tends to trouble it.
Humidity
On humidity, tansy likes things airy and on the dry side, somewhere around 30% to 60%, which is just what most open gardens offer. The only mood it dislikes is damp, still air, so give it room to breathe.
Feeding
Good news for busy hands: feeding is mostly unnecessary, since tansy is right at home in lean ground. A small helping of compost or a balanced fertilizer in spring is all it wants, and anything richer only spurs it to spread more eagerly.
Pruning
Snip off the faded flower heads before they set seed and you have taken care of tansy's biggest habit, its eager self-sowing. When the season winds down, cut the stems back near the ground in late fall or early spring, and the clump will come back fresh and tidy.
Repotting
A potted tansy is happiest divided every 1 to 2 years, before its roots begin to circle and the crown grows crowded. In the ground, lifting and splitting the clump every few years does double duty, giving it a fresh start while gently reining in its reach.
Size & spacing
Depending on how it is treated, tansy rises anywhere from 1 to 5 feet (30 to 150 cm) tall, so leave it a little headroom. Each clump widens to about 9 to 18 inches (23 to 46 cm) across before the rhizomes begin to explore, which is worth remembering when you place it.
When to plant
Tansy keeps the easygoing calendar of a cold-hardy perennial, so there is no rush. Sow your seed indoors in late winter, move the young plants outside after the last frost once the ground has warmed, and the cheerful golden heads will open from July through September.
Northern hemisphere
Southern hemisphere
Typical months for a temperate climate: start earlier in warm zones, later where spring frosts linger.
- Sow: 6 to 8 weeks before the last spring frost
- Plant: After the last spring frost once soil has warmed
- Harvest: Blooms July through September
Hardiness
USDA hardiness zones: 3–8
Temperature: down to -40°C
Troubleshooting
Take heart: most tansy troubles come from a little too much water or from the plant simply wanting to roam, not from any fragility on its part. Watch for the early signs below and a gentle nudge is usually all it takes to set things right.
Tansy wandering into the bed and turning up where you never planted it
Do not be discouraged if tansy starts to roam, because this is simply its aggressive spread at work, and it happens in two ways at once. Creeping rhizomes send fresh shoots well past the parent clump while fallen seed quietly fills the spaces between. Deadhead before the flowers set seed, dig the rhizomes out down to the last little fragment, and keep mowing or cutting the patch through the season until it eases off.
Fix:
- Deadhead before seed set
- Dig out rhizomes including root fragments
- Mow or cut repeatedly through the season
Lower leaves going yellow where the ground stays wet
This one usually comes down to wet feet, and it is an easy fix. Poor drainage or overwatering keeps the soil soggy, the roots go dark and soft, and the lowest leaves yellow to let you know. Loosen things up so the water drains and water a little less often, and a plant this drought-hardy will perk back up before long.
Fix:
- Improve drainage
- Reduce watering frequency
Soft little insects gathering on the tender new tips
Those clustered specks are aphids, soft-bodied little insects that crowd the newest tips and leave a sticky honeydew behind. Knock them off with a firm spray of water, then reach for insecticidal soap only if they gather again. Tansy has a knack for calling in helpful predators, so a few aphids left in place often bring the cleanup crew to you.
Fix:
- Spray with a strong jet of water
- Apply insecticidal soap
Toxicity
This is the part to take seriously, even with such a forgiving plant. All of tansy carries thujone and sesquiterpene lactones that bring on vomiting, drooling, and tremors, and in larger amounts they can harm the organs and, in people, end a pregnancy. Slip on gloves when you tend it, and keep it well away from pets, grazing animals, and little ones.
Toxic to
Cats · Dogs · Horses · Rabbits · Livestock · Birds · People
Cats Toxic
A cat that samples tansy tends to drool and be sick, with diarrhea and a sore, tender mouth following soon after. Keep any larger nibble out of paw's reach, since the thujone inside can lead to tremors and more serious trouble.
Dogs Toxic
With dogs, look for vomiting, diarrhea, and an itchy rash where they have chewed the leaves. A large or repeated helping moves past a simple upset stomach into trembling, seizures, and harm to the liver and kidneys, so it is best kept out of reach.
Horses Toxic
Most horses turn away from tansy at its bitter smell, but one that does take a mouthful ends up with a churning gut and a dull, out-of-sorts mood. The thujone adds up with every bite, so steady grazing risks tremors and strain on the organs.
Rabbits Toxic
The same volatile oils that bother other animals make tansy a poor pick for rabbits, leading to drooling and an unsettled digestion. Leave it off their menu altogether rather than risk even a small taste.
Livestock Toxic
Cattle, sheep, and goats usually pass over the bitter plant, though hungry animals on bare, overgrazed ground may give in and eat it. In any real amount the thujone and sesquiterpene lactones can bring on vomiting, staggering, and convulsions, so fence it off from grazing.
Birds Toxic
The aromatic oils that send insects packing are no gentler on birds, so neither the leaves nor the seed are safe to offer. Treat the whole plant as off-limits for backyard poultry and pet birds alike.
People Caution
For all its long past in old kitchens and remedies, no part of tansy is safe to eat. The thujone can bring on vomiting, drooling, and tremors, it can end a pregnancy, and a real dose harms the organs, so wear gloves when you handle it and keep it well clear of children.
Wear gloves when handling; the aromatic foliage can cause contact dermatitis in sensitive people.
Helpline numbers
United States
ASPCA Animal Poison Control: (888) 426-4435 (fee applies)
Poison Control: (800) 222-1222
Canada
Poison Centres: 1-844-764-7669
Varieties
Most of the tansy you will come across is the plain wild kind, but a couple of gentler garden selections show up now and then for their good looks.
Tanacetum vulgare var. crispum (Fern-leaf or Curly Tansy)
Its leaves come more finely cut, crisped, and curled than the wild plant's, which makes for a neater ornamental that stays a little more where you put it.
'Isla Gold'
Gardeners grow this one purely for its bright golden-yellow ferny foliage, a warm splash of color all on its own.
Companions
Tansy earns its keep next to roses and fruit trees, where its scent helps turn away some pests and draw in beneficial insects, but it's a poor neighbor for small vegetables it can quickly crowd out.
Plant near
Roses: Traditionally interplanted to help deter some insect pests and to attract beneficial predatory insects.
Fruit trees: Used as an aromatic companion thought to repel some pests while drawing in pollinators and predators.
Keep apart
Low-growing vegetable beds: Aggressive rhizomatous spread and heavy self-seeding can crowd out less competitive crops.
How to propagate
Making more tansy could hardly be easier, whether you scatter seed or divide a clump, so the real art is simply deciding when to say enough.
SeedEasy
Spring · Germinates in 1 to 2 weeks; typically blooms by the second year
Scatter seed in spring and, encouragingly, it sprouts in just 1 to 2 weeks, though the plant likes to wait until its second year to flower. Tansy self-sows freely, so snip the spent blooms if you would rather it not settle where it is not wanted.
DivisionEasy
Spring or fall · Establishes within one growing season
Lift a settled clump in spring or fall and pull it into pieces, since nearly every bit of rhizome roots without fuss and finds its feet within a single growing season. It is the quickest way to gain new plants, and a welcome excuse to tame a clump that has stretched past its spot.
Myths
Tansy must be a safe cooking and healing herb, since old recipes leaned on it.
It is true that old cooks and healers once reached for tansy, but time has taught us to be more careful. The plant holds thujone, which makes it unsafe to eat even in small amounts. Enjoy it in the garden and keep it out of the kitchen, and everyone stays well.
A patch of tansy will keep every garden pest away.
Tansy does turn away some insects, so the idea is not made up, but it is no magic fence. It draws in a few pests right alongside the good bugs, so lean on it as one helper among many rather than a cure-all, and you will not be let down.