Gomphocarpus physocarpus

Gomphocarpus physocarpus is commonly known as the balloon cottonbush, in Afrikaans as the balbossie (little ball bush), and previously scientifically as Asclepias physocarpa and A. brasiliensis among other names. The evergreen plant grows from a fibrous rootstock, single-stemmed at the base. It is upright and hairless, branching a little higher up. The pale-yellow, willowy branches are hollow. The growth habit varies, the plant either an annual or a perennial, sometimes a soft shrub of heights from 50 cm to 2 m. These plants mostly live for about two years.

The simple leaves are opposite and narrowly lanceolate to oblong. The margins are entire, the tips sharply to bluntly pointed. The green blades, paler green below than above, have cream midribs and ascending, well-spaced lateral veins prominent on the lower surfaces. The leaf dimensions are from 5 cm to 12 cm long, and from slightly less than 1 cm to 2 cm wide.

The species distribution is widespread in much of South Africa barring the northwest. It is found from the Western Cape and the Eastern Cape through KwaZulu-Natal and Mpumalanga to Limpopo and North West, as well as in several neighbouring countries as far north as Kenya. The photo was taken near Caledon during February.

The habitat is varied, including fynbos, renosterveld, grassland, Albany thicket, and savanna. The plants are often weedy on disturbed land, seen in wetlands, seasonally wet places, and on floodplains. The habitat population is deemed of least concern early in the twenty first century.

Both weed and hardy garden plant that survives light frost, G. physocarpus attracts insects, notably butterflies. The stem fibres have been used in manufacturing garments. Plant parts feature in traditional medicine. The plant has become a weed in at least Australia, the Americas, Hawaii and around the Mediterranean. So, never import or export any plants or seeds ever without following required procedures.

The latex exuded by all plant parts is probably toxic, should not be ingested (Pooley, et al, 2025; Euston-Brown and Kruger, 2023; Curtis-Scott, et al, 2020; Pooley, 1998; iNaturalist; https://redlist.sanbi.org).