Gomphocarpus, placed in the Apocynaceae family is a genus of milkweeds first described as a genus in 1810. It is widespread across much of Africa, with a few species naturalized in other regions. The generic name is derived from the Latin words, gompho, meaning club and carpus, meaning fruit, in reference to the shape of the fruit.

Gomphocarpus physocarpus, commonly known by various names such as Balloonplant, Balloon Cottonbush, Hairy Balls or Milkweed in English and Balbos or Balbossie in Afrikaans and synonymously known as Asclepias brasiliensis, Asclepias physocarpa, Asclepias semilunata, Gomphocarpus brasiliensis and Gomphocarpus fruticosus forma brasiliensis, is a widespread South African indigenous perennial shrub that produces white flowers and inflated hairy fruit capsules and is an excellent butterfly plant. Gomphocarpus physocarpus is an upright, soft shrub 0.5 to 2 m tall with a fibrous rootstock. Cream to white flowers in pendulous clusters are borne almost throughout the year but mainly during summer (November to April). The flowers are attractive and have a complicated structure. The petals bend strongly backwards, arching over the flower. In the centre of the flower is the corona, consisting of five pouched lobes that develop from the petals. The petals are white and the corona is suffused with pink or purple. Gomphocarpus physocarpus is widely used in traditional medicine in South Africa. The roots are used to treat stomach ache. Leaves are dried and ground into a powder that is taken as snuff for headaches. The milky latex is used to treat warts. Seeds are blown away from the pods as a charm to placate the ancestors. The stems are used for fibre. Fresh stems and leaves stuffed into mole holes are said to be an effective deterrent. This plant is poisonous if ingested and has caused death to sheep fed large amounts. It attracts butterflies, in particular the African monarch, to the garden, both to feed on the nectar in the flowers and to lay their eggs on the plant. The inflated fruits last well in the vase, when dried, and can be used in fresh and dried floral arrangements.