Lycium is a genus of flowering plants in the nightshade family, Solanaceae. Lycium are shrubs, often thorny, growing 1 to 4 meters tall. The leaves are small, narrow, and fleshy, and are alternately arranged, sometimes in fascicles. Flowers are solitary or borne in clusters. The funnel-shaped or bell-shaped corolla is white, green, or purple in colour. The fruit is a two-chambered, usually fleshy and juicy berry which can be red, orange, yellow, or black. It may have few seeds or many. Most Lycium have fleshy, red berries with over 10 seeds, but a few American taxa have hard fruits with two seeds. While most Lycium are monoecious, producing bisexual flowers with functional male and female parts, some species are gynodioecious, with some individuals bearing bisexual flowers and some producing functionally female flowers.

Lycium ferocissimum (African Boxthorn or boxthorn) is a shrub in the nightshade family (Solanaceae). The species is native to Cape Province and Orange Free State in South Africa and has become naturalised in Australia and New Zealand. It is listed on the Noxious Weed List for Australian States and Territories and is a declared noxious weed in the United States. African Boxthorn is a large shrub which grows up to 5 metres high and is covered in spines. The leaves are oval in shape and are 10 to 40 mm long and 4 to 10 mm in width. The solitary flowers emerge from the leaf axils and are purplish.