The form "incahuasii", with greener and thinner stems, branches profusely and forms large clumps with more than 100 heads.
The flowers are a deep purple and very showy.

Family: Cactaceae (Cactus Family)

Scientific Name:Puna subterranea (R. E. Fries) R. Kiesling forma incahuasii

Conservation status:  Listed in CITES Appendix II

Distribution: Incahusi peak on the Chile-Argentina border.

Etymology: The genus  name “Puna”derives from theindigenous word "Puna"that indicate the western region up to 4500 m that extends from the Peru, going throughout Bolivia to the Argentinean North. Delimited  at west by a costal chain of high volcanic picks and by the Cordillera mountainous chain to the east. The Argentinean Puna is the natural continuation of the Bolivian highland.

Synonyms:  

• Maihuenopsis subterranea (R. E. Fries) E. F. Anderson 1999
• Opuntia subterranea R. E. Fries 1905
• Pseudotephrocactus subterraneus (R. E. Fries) Kreuzinger 1935
• Tephrocactus subterraneus (R. E. Fries) Backeberg 1935
• Cumulopuntia subterranea (R. E. Fries) F. Ritter 1980
• Puna variiflorus
• Tephrocactus variflorus Backeberg 1962 (non val. publ.)

Puna subterranea forma incahuasii This is a pretty form with with  greener and thinner stems that clumps prufusely and may forms large clumps with more than 100 heads.
The flowers are bright purple and very showy.

Morphology (Identifying Characteristics): The Puna subterranea is a small plant geophytic opuntioid cacti with very tuberous root which in remains half buried in habitat, showing approximately 1 cm. from the ground. Plants have usually few segments (up to 6). But at the northern localities this species can grow with dozends of segments. The form "incahuasii" with  greener and thinner stems forms large clumps with more than 100 heads. This species is very variable and there are many forms of Puna subterranea. It looks like a small Tephrocactus, but the bloom, fruit and the seeds clearly show its autonomous nature.
Stem: Grayish-green, to brownish, round in cross section, elongate, up to 6 cm wide and (but usually less around 15-18 mm in diameter) and 2-4 cm tall. The stems reduces greatly in volume during the dry season often retracting the plant underground.
Tubercles: Rhomboidal.
Roots: This plant has deep tuberous roots with only 1 to 3 cm growing above ground level.
Spines: 1 to 7(-10) pectinated, more or less bent toward the plants body.
Glochids: None or few in the basal areoles about 1 mm long.
Leaves: The leaves are very small and fall off early.
Flowers: The blossoms 2,5 to 3 cm. long have a larger diameter than the segments is one of the reasons why Puna subterranea sometimes is named 'Rebutia of the Opuntias'. At North of Argentina the colour of the blossoms is rather variable; each specimen seem to show a different colour. The flower colour ranges from brown to deep rose red to a pale yellowish rose and rare, but possible with almost white. Pericarpels without areoles but with a few scales bearing hairs and long bristles in the axils. The flowers of the form "incahuasii" are a deep purple and very showy.
Blooming: Time The flowering is diurnal and takes place during the summer.
Fruit: Globose, 12-15 mm in diameter, dry indehiscent (it cannot open by itself )
Seed: 4 mm large covered with a tender arillum.

Growing tips: This species resists cold well if it is dry and need to be kept in a cool place during winter rest (this is important for the flowers as well as for their health) Without this cool winter period they normally wont get many buds.. This mountain cactus - because of the elongated fat taproot - necessitate deep pots and a well drained mineral potting mix. They are susceptible to overwatering,  but need enough water during vegetation. Requires full sun. Specimens in culture, in special grafted ones, presents a bigger amount of glochids than the ones growing in their habitat. Need a sufficient amount of air.

Propagation:  Usually propagated by cuttings and grafting . Grafted plants in culture are most common  and sprout strongly. But it is also feasible to root them but they grow much slower on their own roots and takes various years prior to they bloom.