Strychnos is a genus of flowering plants, belonging to family Loganiaceae (sometimes Strychnaceae). The genus includes about 100 accepted species of trees and lianas, and more than 200 that are as yet unresolved. The genus is widely distributed around the world’s tropics. The genus is noted for the presence of poisonous indole alkaloids in the roots, stems and leaves of the plant. Among the alkaloids are strychnine and curare.

Strychnos pungens is a tree which belongs to the Loganiaceae family. Usually it reaches about 5m in height and occurs in mixed woodland or in rocky places. The Spine-leaved Monkey-orange has branches that are short and rigid with leaves that are smooth, stiff, opposite, elliptic and with a sharp, spine-like tip. It is naturally found on the Witwatersrand, Magaliesberg and further north to northern Namibia, northern Botswana and Zimbabwe. The fruit is large (120mm diameter), round and with a smooth hard shell, bluish-green in colour and turning yellow when ripe. The pulp of ripe fruit is rich in citric acid and is edible, but the seeds are mildly poisonous. The tree is a close relative of Strychnos nux-vomica, the source of strychnine.