Tribulus terrestris



Tribulus terrestris

L. 1753

pronounced: TRY-bew-luss tuh-RESS-triss

(Zygopjyllaceae — the caltrop family)


common names: bindii, caltrop, cat-head

This is a very similar plant to Tribulus cistoides, although on a smaller scale –the leaves, the flowers and the burrs are all rather smaller. Caltrops are devices with 4 metal points arranged so that when any 3 are on the ground, the 4th spike projects upwards. This was a weapon used in mediaeval times by foot soldiers to slow down attacking cavalry. Handfuls of caltrops were thrown down in the path of the horses, and the upward-pointing spikes damaged the hooves. It was not a new invention in the Middle Ages. Roman soldiers had used a similar weapon in classical times, but they called it a tribulus. The Romans gave the same name to a water-plant that had a prickly nut, and Linnaeus used that name for this genus.

Devices working on a similar principle to the caltrop are still used in some places by police, to puncture the tyres of would-be escaping vehicles. The word caltrop comes from an Old English word calcatræppe, ‘foot-trap’.; terrestris is Latin for ‘of or belonging to the earth’ – growing on the ground.

It is native to the Mediterranean at least, and is now a cosmopolitan herb. It is a prostrate annual with stems to about 1 m long radiating from the crown of a taproot, and often branching. In shade, or among taller plants, the plant may grow in a more upright fashion. The leaves are opposite, paripinnate, with 4 – 8 pairs of oblong leaflets, each leaflet less than 6 mm long. The flowers have 5 lemon-yellow petals. About a week after each flower blooms, it is followed by a fruit that easily falls apart into 4 or 5 single-seeded nutlets. These are hard, and bear 2 larger and 2 smaller spines per fruit segment, sharp enough to puncture bicycle tyres and to give a painful injury to bare feet.

Tribulus terrestris has long been used in traditional medicines, especially in the Ayurveda and Unani systems. It is believed to contribute to overall physical and sexual strength, and is an ingredient in many tonics. It is also believed to be useful in kidney, bladder, urinary tract and uro-genital-related conditions, where it acts as a diuretic.

In the mid-1900s the herb became notorious as a ‘secret weapon’ employed by Bulgarian weightlifters to increase muscle growth. It is believed to work by increasing the body’s lutenising hormone produced by the pituitary gland. The lutenising hormone in turn stimulates the testes to boost production of testosterone, which then improves the body’s ability to build muscle mass and strength. Some of the experimental studies used to establish the plant’s reputation as a muscle-builder are rather questionable.

dangerous 2In any case, products based on the plant should not be used by pregnant women, or by people suffering from breast or prostate cancer. Stock grazing the weed develop staggers and nitrate poisoning, young sheep being particularly sensitive.

This is a troublesome weed of wasteland, pasture, cropping, vineyards and recreational areas, and is very hard to eradicate. In smaller areas it is best controlled with manual removal, using a hoe to cut the plant off at its taproot. Even better is pulling by the whole plant, including the taproot, by hand. Few of the chemical pesticides available are effective on the weed. Two weevils, Microlarinus lareynii and M. lypriformi, native to India, Italy and France, were introduced into the US in 1961 to act as biological control agents. The former is a seed weevil that deposits its eggs in the flower bud or the young burr. The larvae feed on the seeds before they pupate. The other weevil is a stem weevil that places its eggs on the undersides of stems, branches, and the root crown. The weevils are most effective when both are used together.

The plant is host to the larvae of several Lepidoptera species, including:

      • the Australian Striped Hawk Moth Hyles livornicoides;
      • the Croton Caterpillar Achaea janata; and
      • the Dark Grass Blue Zizeeria karsandra.


Information about medicinal qualities of plants, or about their use as medicines, is for interest only, and is not intended to be used as a guide for the treatment of medical conditions.


Photographs taken by the roadside in Nelly Bay 2014.
Page last updated 23rd April 2019