Native to Eurasia, common tansy (Tanacetum vulgare) made its way to Canada and British Columbia in the 1600s as an alleged cure for joint pain, and for its uses as a companion plant to cucumbers, squash, and roses. It was known to repel garden pests like ants, cucumber beetles, Japanese beetles, and squash bugs. It was also used in early embalming practices.
Despite these uses, common tansy is an invasive plant in BC that displaces native vegetation, and infestations may be toxic to grazing livestock if digested in large quantities.
Invasive plants grow rapidly and spread quickly, causing damage to the environment, economy and our health; they are the second greatest threat to biodiversity after habitat loss.
Common tansy is currently distributed in the following areas of BC: Bulkley Nechako, Central Kootenay, Columbia-Shuswap, East Kootenay, and North Okanagan Regional Districts, and within Greater Vancouver, Fraser Valley, southeast coast of Vancouver Island, Gulf Islands, Sunshine Coast, and Squamish/Pemberton.
Common tansy plants grow up to 1.8 metres in height, with clusters of dense, yellow button-like flowers that occur at the tops of the stems.
This invasive plant is a perennial species that prefers sunny areas with well-drained soils. It infests stream banks, pastures, and other disturbed sites such as roadsides. It reproduces by seeds that can remain viable in the soil for up to 25 years! These seeds can be transported quickly to new areas by birds, animals, and on vehicles that have been working in infested areas.
Because of its long medicinal and horticultural use, common tansy is still available in plant nurseries and from herbal remedy suppliers. Gardeners should avoid purchasing common tansy.
You can keep this plant at bay in your garden with frequent tilling. This will deplete the food energy stored in its roots. The most effective control method combines mowing or hand cutting with chemical control, and encouraging competition from native vegetation.
Invasive plants vary greatly in western Canada's diverse climates. To find out more about invasive plants in your area or to seek alternative plants, visit www.bcinvasives.ca or phone 1-888-WEEDSBC or (250) 305-1003.