Erect biennial thistle <1.5m tall. Stout, branched, fleshy taproot. Rosette leaves usually long & deeply cut into narrow lobes with spiny edges, have a metallic sheen to the upper surface & a whitish edge zone. Large purple flowerheads droop or nod when mature; a single plant can produce ˜100 flowerheads, each of which produces about 200 seeds.
Pasture, roadsides, wasteland, lucerne crops, hill country grassland. Prefers light, free draining soils with low to medium rainfall.
Seeds dispersed locally by wind & also in mud, water, fodder, seed & by machinery.
Serious threat to pasture, as it grows in dense patches achieving almost total ground cover. Not readily grazed; can cause contamination in wool & harbour pests (eg rabbits).
Good pasture management can prevent establishment. Prevent overgrazing especially in summer. Ensure biocontrol agents are present.
1. Grub out scattered plants or small infestations; remove at least first 5cm of taproot.
2. Weed wipe, all year round (300ml glyphosate/1L or 1g metsulfuron/1L).
3. Spray lightly, not to run off, spring - summer (100ml glyphosate + 20ml penetrant/10L) or winter (3g metsulfuron + 10ml penetrant/10L). Avoid water contamination.
4. Boom spraying established infestations (2,4-D ethylhexyl ester 2-2.5l/ha).
Caution: when using any herbicide or pesticide PLEASE READ THE LABEL THOROUGHLY to ensure that all instructions and safety requirements are followed.