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Bushy perennial grows 30 cm to 1.8 meters tall
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Introduced from Europe in the 1600s for medicinal use
Common tansy
(Tanacetum vulgare)
Quick Identification
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Dark green fern-like leaves
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Stems often purplish-red
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Yellow, button-like flowers in a dense, flat-topped cluster
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Leaves and flowers are aromatic when crushed.
Impact
Often infests stream banks, pastures, and other disturbed sites such as roadsides but can not effectively establish in frequently tilled soils. This species continues to be cultivated in gardens around the district.
Management
Common tansy can be mowed before flowering to eliminate seed production. This method may have to be repeated several times for many to eliminate re-growth from rootstocks. Some selective herbicides are effective for controlling this species.
Flower
Dense, flat-topped clusters of 20 to 200 yellow-orange, button-like flowers at tops of stems. Flower heads consist of disk flowers surrounded by a ring of ray flowers that lack petals. Greenish-brown bracts below the flower heads overlap in 2 to 3 rows and have papery tips.
Leaves & Stems
Dark green, fern-like leaves are deeply divided into leaflets with toothed margins and are dotted with small pitted glands. The stem leave alternate. There are several branched stems per plant which are green or purplish-red, and dotted with glands. Plants are somewhat woody near the base and have a strong odour.
Reproduction & Dispersal
Common tansy spreads by seeds, creeping roots and root fragments. Vehicles, water ways, equipment, and infested gravel or hay can bring seeds and roots to new sites.
Seeds
Oblong, tan to gray, five-angled seeds, 1.5 mm long. Can produce over 50,000 seeds.
Roots
Extensive, short, thick creeping roots, or rhizomes, with numerous lateral roots.
Preferred Habitat
Disturbed areas, stream banks, riverbanks, waterways,
roadsides and fields. Prefers full sun and well-drained
soil.
Interesting Facts
Has been used medicinally to expel intestinal worms, to repel insects, and to stimulate menstrual bleeding. Toxic if ingested in large quantities, but can be grazed safely by sheep and goats.
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