Tansy (bitter buttons) care

Light

Most houseplants will scorch where tansy thrives. Give it the windowsill you'd otherwise leave empty because everything else burned there. Full sun gives the densest growth and most flowers; tolerates light shade but becomes lax and flops more readily. A plant moved abruptly from low light to direct sun bleaches in 48 hours — always acclimatise over a week.

Watering

Aim for drought-tolerant once established; water occasionally in prolonged dry spells for tansy, but treat that as a starting point rather than a rule. A south-facing summer windowsill will dry the pot twice as fast as a north-facing winter room. Lift the pot; if it feels noticeably lighter than it did wet, water it. Established plants rarely need watering. Avoid wet, poorly drained sites, which encourage rot; moderate moisture suits young plants until rooted.

Soil and pot

Tansy grows best in average to poor, well-drained soil. Thrives in lean, dry to medium loam, pH 5.5-7.5. Adapts to roadside gravel and clay; rich soil makes it taller, floppier and even more aggressively spreading. A pot with a working drainage hole is non-negotiable for this species — even free-draining mix will turn soggy in a closed planter. If you love the look of a decorative pot without a hole, use it as a cachepot around an inner nursery pot you can lift out to water.

Humidity and temperature

Tansy sits happiest at around 40-70% humidity and -30 to 30°C (-22 to 86°F). An outdoor border and meadow herb unaffected by ambient humidity; good airflow simply reduces foliar disease. If you keep the room above year-round and avoid placing the plant near a cold draught, a hot radiator, or an air-conditioning vent, you have already handled the two biggest indoor stressors.

Fertilising

Feed tansy sparingly. Needs little to no feeding; it grows lush in poor ground. Skip nitrogen-rich feeds, which worsen flopping and spread. A light spring compost mulch is more than sufficient. Skip fertiliser entirely on a stressed, recently-repotted, or actively wilting plant — fertiliser salts make damage worse, not better. Wait for a round of healthy new growth before resuming a feeding rhythm.

Common problems

Below are the issues we see most often on tansy in the Growli community. Each is annotated with the most common cause so you know where to start.

• Invasive spreading — Vigorous rhizomes form dense colonies and it self-seeds freely; it is a listed noxious weed in some US states. Plant with a root barrier or in a contained bed and deadhead before seed set.
• Flopping in rich soil — Tall stems sprawl in fertile ground or shade; grow hard in lean soil and full sun, or cut back by half in early summer for sturdier regrowth.
• Aphid infestation — Aphids cluster on soft new shoots and flower stems; tolerate minor numbers (tansy attracts beneficials) or dislodge with a water jet.
• Powdery mildew — White coating develops on foliage in crowded, humid conditions; thin clumps and improve airflow to prevent it.

Propagation

Easiest by division of the spreading rhizomes in spring or autumn; also grows readily from seed sown in spring and from softwood cuttings, though division gives the fastest establishment. Propagation is the cheapest, most satisfying way to expand a collection — and it doubles as insurance against losing a mature plant to an accident. Take a backup cutting once the parent is established and healthy.

Toxicity to pets

Tansy is toxic to pets. Tansy is not individually catalogued by the ASPCA, but it is well established in veterinary and toxicology literature as poisonous: the foliage and flowers contain thujone and other volatile oils. Ingestion can cause vomiting, diarrhoea, tremors, convulsions and, with the concentrated oil, liver and kidney damage. Keep away from cats, dogs and livestock; the essential oil is especially hazardous. If you keep cats, dogs, or curious children in the house, weigh placement carefully — a high shelf or a hanging planter is enough for casual safety. For severe ingestion incidents, call your local vet and the ASPCA Animal Poison Control Center (in the US, 888-426-4435).

Pet-safety status is sourced from the ASPCA Toxic and Non-Toxic Plant List, which catalogues the most-asked-about plants for cats, dogs, and horses.

Tansy deep-dive guides

Every aspect of tansy care, each with its own calibrated guide:

• Tansy watering schedule
• Tansy light requirements
• Best soil mix for tansy
• Tansy fertilizing guide
• When to repot tansy
• How to propagate tansy
• Tansy growth rate & size
• Tansy cold hardiness
• Tansy temperature & humidity
• Is tansy toxic to cats & dogs?
• Is tansy toxic to cats?
• Is tansy toxic to dogs?

Related guides

Tansy is also known as tansy, common tansy, and bitter buttons.

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