Common tansy produces dense clusters of golden yellow flowers in button-like heads held above dark green fern-like leaves. Tansy was originally introduced from Europe as an ornamental and a medicinal herb. It is a robust, erect perennial that can grow up to 2m tall and also has insecticidal properties.
How does it spread?
Plants are known to produce thousands of wind-blown seeds, but it also spreads easily by rhizomes and root fragments. Seeds are often distributed by wind, water, wildlife, humans and in contaminated hay bales, and on vehicles and equipment.
Where would I find it?
Tansy flourishes in full sun in moist, rich soil, such as on stream banks, or in ditches or moist pastures, roadsides, waste areas, but it cannot establish well in tilled soils. It can also can establish in poor, dry soils.
What problems does it cause?
Common tansy forms dense monoculture stands and displaces native vegetation thereby reducing wildlife habitat and species diversity. The leaves contain alkaloids that are toxic to animals and humans if eaten in quantity or absorbed through the skin. If preferred forage is lacking, grazers may ingest the unpalatable leaves which can cause abortion and/or taint dairy milk. In riparian areas, Common tansy can reduce native vegetation which impacts stream bank stability.
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