Also known as
Senecio jacobaea, tansy ragwort, St James’ wort
Where is it originally from?
Europe, West Asia
What does it look like?
Smelly biennial or perennial (occasionally annual) herb (<30-120 cm tall), with a tap root (crown) with numerous fibrous roots extending 30+ cm. Wavy, lobed leaves (5-20 x 4-6 cm) emerge initially from a basal rosette, and stem leaves are deeply cut, clasp the stem, and have no broad terminal lobes. Erect, rigid stems (50-120 cm) are single (multiple in perennial plants), usually purplish and usually branch above the middle. Yellow, daisy-like flowers (<2 cm diameter, Nov-Apr) with golden yellow centres have 11-13 yellow petal-like florets in compact, flat-topped clusters at the ends of stems. Seeds are like thistledown.
Are there any similar species?
Marsh ragwort (Senecio aquaticus) is a very similar exotic that has established in the wild. Also the native groundsel and fireweed Senecio species that are mostly unique to New Zealand are similar.
Why is it weedy?
Matures quickly, and produces massive numbers of viable, long-lived, widely dispersed seeds that can rapidly colonise bare spots, light gaps and margins in full or partial light. Tolerates very hot to very cold temperatures, very wet to moderately-dry conditions, most soil types, and a little shade.
How does it spread?
Wind spreads seeds over great distances, and they are also spread by water, soil movement, contaminated machinery, livestock, lime, clothing and hay.
What damage does it do?
Forms dense stands in disturbed and grazed areas, and can (usually temporarily) prevent the establishment of seedlings of native plant species.
Which habitats is it likely to invade?
Invades disturbed forest and shrubland, short tussockland, fernland, herbfield, wetlands, inshore and offshore islands, river systems, bare land, and coastal areas throughout New Zealand.
What can I do to get rid of it?
Always ensure plant is ragwort before treating.
1. Spray rosette plants (winter-spring only, before stem formed): 2,4-D (50ml/10 litres (knapsack) or 1-3 litres/ha in 300 litres water (boom spraying)).
2. Spray: cut any seedheads and dispose of by burning or deep burial, apply glyphosate (100ml/10L knapsack) or metsulfuron-methyl 600 g/kg (5g/10L knapsack) ensuring entire plant is covered.
Damaged plants (from cutting, digging, pugging, mowing or poor spraying) usually regrow, form large additional root crowns (multicrown) and become perennial, ie. flowering annually and not dying. These plants do not respond to 2,4-D herbicide, requiring tougher, more residual herbicides.
What can I do to stop it coming back?
Ragwort can be left in regenerating bush and shrubland as will disappear as light levels fall.