Tansy is an invasive weed native to Europe. The origin of its generic name is not clear. Clark speculates it is probably the Latin word athanasia which means undying, referring to its use as a medicinal herb or its long-lasting flowers (L.J. Clark, 1998, Wild Flowers of the Pacific Northwest). The specific name vulgare means common, and tansy is very common in Oregon.
Tansy grows upright in large clusters. There is little branching on upper stems.
Tansy grows up to 5 feet tall, and is typically several feet wide.
Foliage is deeply and pinnately dissected with toothed margins.
Foliage is arranged alternately along the stem. Stems are often dark brown to purple in color, but can also be green when juvenile.
Flowers occur in terminal clusters called cymes.
Structure of flower clusters are often more obvious when viewed from underneath.
Flowers are all tubular or disk flowers. Flowers are yellow in color, and mature to dark brown.
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