Distribution Tansy ragwort is native to Europe, Asia and Siberia, extending north as far as Norway and south into Romania, Hungary, and Bulgaria. It has been introduced into Australia, New Zealand, South Africa, South and North America. In North America it is established in areas with cool, wet, cloudy weather. It was first recorded in California in 1912 and in Oregon in 1922, and by the mid 1950s had become an important weed of the Pacific Coast. It occurs on both coasts, in the east from Newfoundland to New England and in the west from British Columbia to Northern California.
Ragwort occurs on many different soil types, particularly on light to medium, well-drained soils.
Although Ragwort rarely grows in annually tilled lands, it can invade grasslands, disturbed areas, forests, pastures, and wooded pastures. The flattened rosette overtops and kills the surrounding vegetation, either by allelopathy, light limitation, suffocation, physical suppression, or some or all of these in combination. Most individual plants die after flowering, creating a gap suitable for immediate colonization by seedlings. Ragwort reproduces mostly from seed, but regeneration of shoots can occur from crown buds, root fragments, and intact roots. Disturbance or injury promotes vegetative propagation.