Key Facts
- Perennial herbaceous plant with ferny leaves
- Distinctive buttonlike yellow flower clusters in summer
- Native to Europe and Asia and introduced elsewhere
- Spreads by rhizomes and can form dense clumps
- Often considered invasive in parts of North America
- Contains toxic compounds and can be harmful if ingested
- Propagated by seed and by division of rootstock
Tansy is a herbaceous perennial with ferny leaves and buttonlike yellow flower clusters that appear in midsummer. It spreads by rhizomes and can form dense clumps, so plant it where persistence and potential spread are acceptable.
Identification and appearance
Tansy reaches about 2 to 4 feet tall and typically spreads 1 to 3 feet though colonies can expand beyond that by underground stems. Flower heads are small and buttonlike, clustered into flat topped sprays in midsummer, while leaves are deeply divided and feathery.
Where to grow and common uses
Use tansy for informal massing, rough borders, or naturalized edges where a tough, spreading perennial is wanted. It performs best in full sun and tolerates some light shade, with best flowering in sunny sites.
Hardiness is reported roughly for USDA zones 3 to 8, but local performance varies so confirm for your area.
Soil light and watering
Tansy adapts to average to poor soils and tolerates dry and heavier soils as long as they drain. Avoid sites that stay waterlogged because wet soil often leads to decline. Once established the plant shows moderate drought tolerance, while extra moisture can encourage faster spread but also cause problems in poorly drained ground.
Planting timing and spacing
Space plants about 30 to 90 centimeters apart, roughly 1 to 3 feet depending on how quickly you want it to fill in. Divide established clumps in spring or fall to propagate and to manage vigor. Seed will also self sow and can increase local abundance.
After flowering care and maintenance
Remove spent flower heads to reduce self sowing and to keep plants tidy. Division every few years helps refresh clumps and is an effective way to remove spreading rhizomes. If you do not want it to naturalize, pull or dig up new shoots and rhizome fragments promptly.
Managing spread and invasiveness
Tansy spreads by rhizomes and can form dense patches that outcompete neighbors in favorable conditions. It is considered invasive in parts of North America, so check state or provincial invasive species lists before planting. Confinement options include regular division, removing flower heads, and installing deep root barriers to limit underground spread.
Propagation
Propagate by division of clumps or by planting rhizome pieces in spring or fall for reliable clonal plants. Tansy also grows from seed, and self sowing contributes to naturalization so remove seedheads when containment is desired.
Toxicity and safety
Tansy contains toxic compounds including thujone. Ingestion can cause vomiting and other serious effects and dermal contact may cause skin irritation. Take care around children, pets and livestock and confirm specific risks with local poison control or extension resources.
Frequently asked questions
- How fast does Tansy grow?
- Growth rate varies with site and climate. It forms clumps and spreads by rhizomes, and in favorable conditions can expand into dense colonies beyond the original planting width.
- Is Tansy invasive?
- It can be invasive in some regions, especially where it naturalizes from seed and spreads by rhizomes. Check local invasive species listings and manage by removing flower heads and dividing plants.
- Is Tansy poisonous to pets and livestock?
- Yes. The plant contains volatile and toxic compounds that can be harmful if eaten and may irritate skin. Confirm severity with local poison control for species specific guidance.
- When does Tansy bloom?
- Flowers appear in summer with peak bloom often in midsummer, typically July to August in temperate northern hemisphere climates.
- Can I propagate Tansy by division?
- Yes. Division in spring or fall is a reliable method and also helps control spread when you remove unwanted rhizome pieces.
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