Tansy (Tanacetum vulgare)

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Sunlight Full sun to partial shade; performs best in sunny, well-ventilated locations and tolerates dry, exposed conditions

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Watering Water deeply when the top 5 cm of soil is dry; drought-tolerant once established, avoid overwatering to prevent root rot

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Temperature Extremely cold-hardy; thrives in cool to temperate climates and can withstand winter temperatures as low as -30°C

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Leaf: Fern-like, deeply divided, aromatic green leaves with toothed margins
Flower: Dense, flat-topped clusters of bright yellow button-like composite blooms
Stem: Erect, rigid, slightly hairy green stems with branching upper portions

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Watering

Keep soil consistently moist during active growth; allow top layer to dry slightly between waterings

Fertilization

Light, diluted organic feed once monthly. Avoid high-nitrogen fertilizers to prevent excessive foliage at the expense of blooms

Eggshell powder topdress：Sprinkle finely ground, dried eggshells on soil surface; avoid direct contact with stems to prevent fungal growth

Pruning

Deadhead spent blooms regularly to extend flowering period
Cut back stems to ground level in late autumn to promote vigorous new spring growth
Thin overcrowded clumps every 2–3 years to improve airflow and reduce disease risk
Remove yellowing or damaged foliage to maintain plant health

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Warning: this plant may be toxic.

Pets & Humans

Pets: ASPCA: Toxic; ingestion may cause vomiting, diarrhea, depression, and seizures in severe cases

Humans: Contains thujone; ingestion causes nausea, vomiting, and abdominal pain; toxic in large doses, especially for pregnant individuals

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Culture: Historically used as an insect repellent and folk medicinal herb; modern use is discouraged due to toxicity

Usage: Ornamental garden plant; natural pest deterrent for aphids and other small insects