Invasive Watch: Common tansy
WHAT TO LOOK FOR
Common tansy, also known as garden tansy and golden buttons, is a perennial, herbaceous flowering plant in the aster family. Plants are typically 3 to 5 feet tall with erect stems, distinguishable by clusters of small, buttonlike, yellow flowers that lack ray petals. Leaves are alternate and pinnately compound and irregularly lobed with leaves becoming smaller toward the tip of the stalk. Leaves and stems have a strong smell if crushed.
The plant reproduces by seeds and rhizomes. Its flower heads are capable of holding seeds though the fall, when they may be dislodged from the dried flower head and spread by wind, birds, animals, vehicles and water. More established plants are also capable of spreading by creeping rhizomes, which form dense patches.
WHERE IT’S FOUND
Common tansy is found throughout nearly the entire United States, having been reported in all states except Texas, Alabama, Georgia, South Carolina and Florida. Once established, it’s aggressive in forming dense stands that displace desirable forbs and grasses, impacting wildlife habitat, and often is found along with other noxious weeds like Canada thistle and knapweeds. It is commonly located in recently disturbed sites, including along roadsides, river banks, stream banks, pastures and irrigation ditches.
Common tansy was introduced from Europe in the 1600, and because of its medicinal uses and popularity as an ornamental planting, it was planted and cultivated in the yards and gardens of early settlers. It is currently designated as a noxious weed in five states.
HOW TO TREAT IT
Apply Opensight® specialty herbicide at 2.5 to 3.3 ounces per acre in a high-volume broadcast application. Use the higher rate when weeds are larger and apply to vegetative state prior to bloom. It may be necessary to monitor treated areas for several years to spot new plants germinating from the seedbank or resprouting from rootstock.