Common ragwort (Senecio jacobaea)
This is the only ragwort species specified in the Weeds Act 1957; other species of Senecio are not so widespread as common ragwort. Flowering is from late June onwards to early autumn when the characteristic yellow inflorescences usually extend between 30 to 100cm in height.
The weed occurs in neglected grass fields, on uncropped ground and sand dunes. It prefers light soils of low fertility, particularly in over or under-grazed pasture. Common ragwort is biennial when undisturbed but can develop perennial characteristics following cutting or treading.
Poisonous to livestock
Cattle and horses are particularly susceptible to poisoning by common ragwort but sheep are also susceptible. Palatability of the weed increases when plants are conserved in hay or silage or treated with herbicide. An added problem is that livestock cannot easily reject fragments of ragwort in conserved herbage and its poisonous alkaloids are unaffected by the conservation process.
Although short-term action can be undertaken to clear existing plants, re-infestation will be rapid unless overall husbandry is improved, particularly for uncropped ground and grassland.
Cutting and stem removal at the early flowering stage reduces seed production but does not destroy the plant. Cut plants left lying in the field are a serious risk to grazing animals and may still set seed. These should be removed and burned.
Pulling and digging:
Pulling or digging can also prevent seed spread but may not give long-term control. Plants should be removed and burned.
No single herbicide treatment will completely eliminate a ragwort infestation due to successive germinations of the weed. Treatment with selective herbicides can be made to the plant rosettes usually late spring and in the autumn before frost damages the foliage. The most effective material for overall spraying is 2,4-D* but this will damage clover and a number of other plant species.