Tansy Ragwort: spot it, stop it, and protect animals

One plant can quietly ruin a herd. Tansy ragwort (Senecio jacobaea) contains compounds that damage the liver in horses, cattle, and sheep. Animals rarely eat healthy green pasture, but dried ragwort in hay is deadly. If you manage land, you need to know how to find and remove it fast.

How to identify tansy ragwort

Look for upright stems with clusters of bright yellow, daisy-like flowers from mid-summer to autumn. Leaves are deeply lobed and feel slightly hairy; young plants form low rosettes in spring. Plants grow 30–100 cm tall when flowering. The flower heads are smaller and more clustered than common tansy; each head has a yellow disc with tiny ray petals.

Confused with other yellow wildflowers? Check the leaves and the timing: ragwort rosettes in spring turn into tall, branched stalks by summer. If you see lots of rosettes in pasture, expect more flowering plants later in the season.

Practical control and prevention

Start early. Remove plants while they’re in the rosette stage or before seed sets. Pulling works on small patches—wear gloves and work when soil is wet so roots come out. Do not compost pulled plants. Bag them or bury them deep; seeds can survive and spread if left in compost.

Spot-spraying with a selective herbicide works on larger infestations. Treat rosettes in spring or fall when plants are actively growing. Read and follow local label instructions and rules—herbicide choices and timings vary by region.

Grazing strategies help prevent outbreaks. Avoid overgrazing; healthy pasture competes with ragwort. Don’t let animals graze close to ragwort when plants are flowering or seed is present. Remember: dried ragwort in hay is a major risk, so inspect and avoid cutting ragwort into forage.

Biological control exists in some areas. Cinnabar moth caterpillars and certain flea beetles eat ragwort and can reduce numbers over time. These methods take years and work best combined with mechanical control.

Safe disposal matters. Burn or deeply bury plants where allowed. Never leave pulled plants on the field or toss into hedgerows. If you suspect large infestations or regular outbreaks, contact local biosecurity or agricultural extension for help—many regions have reporting and control programs.

Spotting one plant now can save a pasture and protect animals later. Keep an eye on rosettes in spring, remove before seed set, and improve pasture health so ragwort struggles to return. If you’re unsure about a plant or a control method, ask a local agronomist or extension officer—practical local advice beats guesswork.