P. tuberosus (kuntzei) is a caudex forming plant with thin fragile growth that breaks off easily, but also grows back quickly.

Description: This is a geophyte cactus with huge tuberous roots under the soil ,with thin fragile blue-light to brownish-purple stems that breaks off easily.
Flowers are a pale to deep yellow and the stigma can go from almost white, to pink or to deep red. The flowers are produced from the apex of new growth.

Cultivation: Pterocacti are easy to grow, provided they are kept cold, but dry during autumn and winter.  It is essential to give full sun; otherwise they will become atypical.  If grown in full sun, the new growth will flower profusely in spring and summer.
Most of the slender stems become detached during winter, but some advise to help the plant by pruning all the top growth in autumn, to encourage it to produce stems with terminal flowers in the spring.

Reproduction: Seeds/Cuttings

Pterocactus tuberosus tuber is sometime used as an hardy grafting stock for south-American cacti like tephrocactus malyanus.

The genus pterocactus belong to the subfamily Opuntioideae and has been given its own tribe, the Pterocacteae.

Scientific name:  Pterocactus tuberosus (Pfeiffer) Britton & Rose 1919

Origin:  Northern Argentina  from Rio Negro in the south to Salta in the north and Patagonia. Many different forms exist.

Ecology: this plant has a peculiar reproductive mechanism: they have the ability to lose their sprouts in autumn and winter. These are then spread by strong winds and volatile sands, and can give origins to new plants in the next vegetative season.  The Pterocactus tuberose roots will grow new floriferous stems again.

Conservation status: Listed in CITES appendix 2.

• Pterocactus kuntzei K. Schumann 1892
• Opuntia tuberosa
• Pterocactus tuberosus var. decipiens
• Pterocactus decipiens

Pterocactus kuntzei (tuberusus)
 

The huge Pterocactus tuberose roots.