Centaurea calcitrapa
ASTERACEAE
Red or Purple Star Thistle.
Native to S & W Europe, although rarely found there nowadays has become a noxious weed across the globe.
Multi branched stems forming a dense mat to 1 m tall.
Dark green deeply lobed lowers leaves becoming less divided higher up, 2 to 8 cm x 1 to 3cm with course hairs.
Numerous flowers at the ends of branches or in leaf axils. 1.5 to 2 cm long, bright or pale purple sometimes pink, July to October with surrounding spikes 10 to 30 mm long in 1 to 3 pairs.
Each flower dries to produce about 1000 seeds per plant, that aren’t wind dispersed, rather falling close to the parent plant or being dispersed by water, machinery, fur, wool or contaminated hay.
Cultivation can stimulate germination so combined cultivation & herbicide application can be most effective as long as the thistles are treated at seedling stage, usually winter or spring. Individual plants can be dug out being sure to remove as much of the tap root as possible.