Caltrop (Tribulus terrestris), location unknown
© Harry Rose
Tribulus terrestris plant1
Introduced, warm season, annual or short-lived perennial, prostrate herb with reddish stems to 80cm long and a woody taproot. Leaves consist of 4-8 pairs of leaflets (4-12mm long); leaflets are dark green above and silvery-grey below; hairs mostly restricted to the midrib and margins. Solitary flowers in the axils are small, bright yellow and 5-petalled. Fruit have 5 segments each bearing short hard spines. Flowers from spring to autumn. A weed in pastures and fallowed cropping country. Often found around sheds, laneways and roadsides. In urban areas it is regarded as a nuisance weed on footpaths and playing fields. It easily attaches to machinery, tyres, animals and shoes aiding its spread. The spiny fruit can cause vegetable fault in wool and lameness to stock. Becomes dominant when other vegetation is removed by fallows, droughts or overgrazing. Prevention of spread is the best control measure. Establish competitive pastures to outcompete catheads. A wide range of herbicides can be used. Grazing with cattle is preferred as photosensitisation, nitrate poisoning and staggers in sheep have been known to occur.
Photo taken on 27 Jan 2015