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July 2014 was designated ‘Pterocactus July’ by the TSG.  This article gives a brief overview of the genus and includes illustrations that were submitted.

 The origins of the genus Pterocactus are still somewhat confused. The plant Opuntia tuberosa was first described by Ludwig Pfeiffer in 1837 from material collected near Mendoza in Argentina. Following this, in 1897, the genus Pterocactus and the species Pterocactus kuntzii were described in the same publication by Karl Schumann in 1897 citing material collected in the same area. Extensive research by James Iliff and Nigel Taylor suggest it is highly likely the material both Pfeiffer and Schumann described was the same.  The word Pterocactus is derived in part from the Greek word pteron meaning wing. This refers to the distinctive shaped seed with its broad, papery wing. Pterocactus is one of the few genera which, on the whole, has avoided the wholesale loss of names  to synonymy in recent times. Only skottsbergii, which has been sunk into synonymy with  hickenii and kuntzei and decipiens which have been sunk into synonymy with tuberosus are the only names that are no longer considered good species in their own right.

 Today, nine species are recognised. They all grow in Argentina, throughout Patagonia and into the northwest of the country to Salta. They are characterised not only by their odd shaped winged seed but also by their thin, usually short, semi-erect stems. When they flower there is only a single flower at the very tip of the each flowering stem. In habitat, the plants develop a large underground tuber and the stems are usually deciduous, being shed during the cold winter months.

Photographs by Pete Arthurs, Carolina González, Cyrill Hunkeler, Jiri Kolarik, Norbert Sarnes and Håkan Sönnermo.  Text by Ivor Crook.

An open seedpod on Pterocactus tuberosus HUN352 (photo Cyrill Hunkeler)