Tansy Ragwort

General

Native to Europe and western Asia.
All plant parts are toxic. Poisonous to cattle, horses, goats, pets and people.
Quickly invades newly disturbed areas and displaces quality forage plants due to it’s highly aggressive growth.
May be confused with common tansy and common St.Johnswort both Class C noxious weeds.
- Common tansy is easily identified by yellow, button-like flower heads without petals and fern like leaves.
- Common St.Johnswort flowers have 5 petals and the leaves are much smaller, oppositely arranged and are spotted with tiny translucent dots when held up to the sun.

Identification

Generally biennial sometimes annual or perennial herbaceous plant with a large woody tap-root.
Most tansy ragwort seeds germinate in the fall. Spends its first year in the rosette stage, as a basal clump with dark green ruffled leaves with reddish stems. In the second year, flowering stems bolt generally 2-4 feet tall.
Flowers appear in flat toped clusters, daisy-like in appearance with yellow petals and yellow center, usually with 13 petals. Flowers June to October.
Leaves are dark green on top, whitish-green underneath, with deeply cut, blunt-toothed lobes with a ragged, ruffled appearance. Leaves along the stem are alternating. Leaves are 1.5 – 8 inches long, and 1-2.5 inches wide.

Photos

Habitat

Found on roadsides, pastures, fields, cleared forested and upland areas in riparian corridors.
Prefers full sun and open sites with moderately moist to dry soils.

Reproduction and Spread

Mainly reproduces by seed, although can reproduce vegetatively.
Up to 150,000 seeds per plant; spread by wind, mowing, animals, humans, and vehicles.
Seeds remain viable in the soil for over 10 years.

Control

Contact your county noxious weed control board if you see tansy ragwort, especially where there are horses or livestock grazing.
Pull or dig up the entire plant, root fragments left in the soil can resprout. Wear protective gloves when pulling by hand.
If plants are flowering or seeding, remove these parts and dispose of in the trash, do not put in the compost or yard waste as flowers will still go to seed after pulling.
Mowing alone is not effective as tansy will resprout if the entire plant is not removed however, mowing can prevent plants from going to seed.
For large infestations herbicide treatments may be necessary. For best results spray rosettes in the spring and again to new growth in the fall. Do not cut or allow livestock to browse for 2-3 weeks after treatment.
- Don’t spray plants that have already flowered, cut and bag flower or seed heads, as herbicide applied at that time will not stop seed production and plants generally die after on their own.

Herbicide Control

Triclopyr, dicamba, 2,4-D and aminopyralid are selective herbicides that will not harm grasses
Glyphosate is a non-selective herbicide, but effective on tansy where damage to grasses is tolerable.
After control efforts, plant areas with site appropriate native plants to fill the void and provide competition for future weed establishment. Monitor areas for seedlings and resprouts.