Caltrop Tribulus terrestris
Caltrop is a problematic pest plant both environmentally and in the home garden. This annual herb produces fruit with long sharp spines that are very painful if stepped on.
Caltrop may germinate at any time of the year following sufficient rainfall. Plants can reproduce continuously from spring to autumn and will readily infest bare disturbed soil. Fruit can cling to footwear, clothing, car tyres, bike tyres and animals. This assists the effective spread of seeds across large distances. If left untreated, large infestations can out-compete other ground cover plants including turf.
Remove smaller plants by hand. Remove the entire plant including all roots, pulling plants from the root crown. Wear gloves to avoid sharp spines. Place plants in rubbish bags and tie securely for disposal. Spray seedlings with a 1% glyphosate solution. Alternatively, diesel can be effective in killing plants and sub-surface seeds.