Gomphocarpus

Gomphocarpus is a genus of erect perennials and shrubs in the Apocynaceae or milkweed family. The plants are often short-lived, contain milky sap or latex and sometimes have hollow stems.

Gomphocarpus is related to the Asclepias genus comprising plants that grow from tuberous roots. Gomphocarpus plants grow from fibrous rootstocks. The simple leaves are opposite, variously shaped, their margins entire.

The terminal or axillary inflorescences are mostly nodding, umbel-shaped clusters. The stalked flowers are bisexual and actinomorphic or radially symmetrical. There are usually five sepals.

The spreading corollas are mostly white or pale greenish yellow, at least on their inside surfaces. The corona lobes dilate into hollow sacs or boat-shapes, sometimes with appendages. Pollen is carried in coherent, pendulous masses with short, stalk-like appendages (caudicles) and easily uploaded (and offloaded) by insects.

The fruit is a beak-like follicle, sometimes inflated balloon-like and covered in scattered bristles. The generic name, Gomphocarpus, is derived from the Latin words, gompho, meaning club and carpus meaning fruit, referring to the fruit shape.

The seed is attached to a silky tuft of hairs, the coma, facilitating wind dispersal. Several of the species are commonly called wild cotton on account of this.

There are about 30 Gomphocarpus species in Africa and Asia, 10 of which occur in southern Africa. A few species have become naturalised in other places, as these plants set seed within their first year, may self-fertilise and have many pollinators. This makes some of them effective pioneers, particularly on disturbed ground.

The milky latex of some species is poisonous, but certain butterfly larvae feed on the plants and are consequently poisonous themselves, possibly to some butterfly eaters as well. Steenbok will browse young growth, but these plants are generally unpalatable to game and stock.

The plant in picture is Gomphocarpus cancellatus (Leistner, (Ed.), 2000; Vlok and Schutte-Vlok, 2015; Manning, 2009; Wikipedia; www.phillipskop.co.za; http://pza.sanbi.org).