Caltrop, bindii, cat’s head, cat eye, goat’s head, yellow vine, puncture vine. Whatever you know it as, you know that Tribulus terrestris is a very nasty weed indeed.
The plant is a flat, sprawling, annual herb, appearing over summer and flowering now. Caltrop loves bare ground. Not an unpleasant plant in itself, caltrop is small and quite soft underfoot. The flowers are yellow, with five petals.
Fruit will start to appear after flowering, and the plant takes on a whole new dimension. The fruit of caltrop is a woody burr with sharp rigid spines to about 6 mm long, with the burr about 1 cm in diameter – also known as a bindi. According to Agriculture Victoria, caltrop fruit are formed continually throughout summer and autumn and up to 1,000 fruit can be produced on each plant. Caltrop can produce upward of 20,000 seeds per plant.
The spines of the fruit are it’s way of spreading. These can puncture feet (human and animal), bike tyres, vehicle tyres, rubber-soled shoes and almost any object placed on it. Anyone who has stood on one remembers caltrop!
Now is the time to notice caltrop – and do something before it seeds! If you see a single plant, pull it up by the roots. If it already has bindies developed, put the whole plant in a bag for disposal. The best time for spraying is also approaching; Autumn (March, April, May) and late Spring (Oct, Nov, Dec).