Biology
Nodding thistle is a biennial weed, reproducing by seeds. Stems are erect, unbranched, up to 2.5m tall, and have spiny wings along the stem except just below the flowering head. Leaves are alternate, glabrous, and veined on the underside. Leaf margins are deeply lobed and spiny. The flowers are red to purple in colour and occur at the ends of branches and axils of upper leaves. The seeds are 4 mm long x 1.5 mm wide, light brown with dark stripes, glossy, and topped by a long pappus.

Scouting Techniques
Take a minimum of 20 weed counts across the field. Scout frequently, especially coarse textured soils, for patches of this weed because it spreads very rapidly.

Effects on Crop Quality
Can reduce the quality of desirable plant species by competition.

Threshold/Yield Loss

Control Tips

• Biological control using head beetle, seed weevil (Rhinocyllus conicus) control achieved in 5-10 years in non-crop land
• Group 4 (lontrel) before flowering
• Repeated mowing at early bud stage to reduce root reserves