DevilsThorn (Tribulus terrestris)

We have a few species of plants here known as the Devils Thorn but this is by far the worst.

Devils thorn (Tribulus terrestris) family Zygophyllaceae

Also know as: Puncture Vine, Caltrop, Calthrops, Bullhead, Devil's Thorn, Cathead, Goathead, Mexican Sandbur, Texas Sandbur

 This species bears spiny fruit (burrs) which are about 2cm (1”) in length. The dried fruit is pernicious to the horse, for when the thorn enters the hoof, it completely rots the frog and cripples the horse.

 It is poisonous to livestock. The toxin, a triterpenoid, causes liver damage resulting in photosensitivity (distinctively; unpigmented parts of the skin react to UV light resulting in inflammation leading to swelling etc of particularly the head). This is known to farmers as 'geeldikkop' (yellow-thick-head). Toxicity usually results when livestock (particularly sheep) graze young, wilted plants.

 For homicidal purposes, the poisonous juice of Acokanthera venenata is smeared on a suitable prickly fruit such as that of Tribulus terrestris and strewn on a path which is likely to be used by the victim.