Tansy (Tanacetum vulgare) is a robust, aromatic plant recognized by its clusters of button-like yellow flowers and fern-like, deeply divided green leaves. Its upright stems form dense, shrubby patches that spread aggressively in open areas. Also known as Common Tansy or Bitter Buttons, it is native to Europe and Asia but has become widespread in North America, especially along roadsides, fields, and disturbed sites.

As both a flowering weed and colonizing shrubby weed, Tansy establishes rapidly and forms dominant stands that can crowd out native species. Its foliage has a strong, pungent scent due to volatile oils once used in traditional medicine and natural insect repellents. While toxic to livestock in large quantities, it plays a role in pollinator support and adds bold texture to wild landscapes. Tansy’s historical use in folklore and herbalism, paired with its hardy, self-sustaining nature, makes it both culturally notable and ecologically persistent.