Lobivia aurea fallax 
Bears strong spines and large silky yellow flowers. A superb plant!
 

Description: Solitary or branched.
Stems:  Dark green to grey-green, globular or elongated, reaching a height of 15 cm and a diameter of 4 to 10 cm or more.
Ribs: 14 to 15, sharp-edged, separated by deep grooves.
Spines: 8 to 10 radials, clear radial about 2 cm. long pointing outward, usually 4 central spines, 3 to 6 cm long. The one to four central spines are thicker, about 4 cm (up to 6cm) long, and brown to black with yellow tips.
Flowers: Lemon yellow and bright yellow inside (nearly 10 cm.) long.  Blooms in flushes in late spring and occasionally in summer. Buds are covered by long silky hairs and grow laterally from the centre of the stem.  The tube is slightly curved, funnel-shaped, slender and greenish white, with pale green scales, red at the base, with white and black below.
 

Cultivation: It is a summer growing species that offers no cultivation difficulty.  Water regularly in summer (but do not over-water).  It is rot prone and should be planted in a shallow pot.   Like most Echinopsis cultivated for their blossoms, it needs a soil mixture a little richer than the average cactus, still with excellent drainage.   Keep rather dry in winter.
It is quite frost resistant if kept dry, hardy to  -5°(-18°) C.   It needs a very bright exposure.  Full sun is indispensable to keep plant compact, with strong spines.

Propagation:  Direct sow after last frost, or offsets (if available)

Photo of conspecific taxa, varieties, forms and cultivars of Lobivia aurea (Echinopsis aurea). (This taxon has lots of synonyms (like most Lobivia) whit several controversial varieties and subspecies):

• Lobivia aurea
• Lobivia aurea var. fallax
• Lobivia aurea var. mizquensis
• Lobivia aurea var. shaferi
• Lobivia aurea var. shaferi forma mostruosa

Origin: Northern Argentina

Synonyms:  

• Lobivia aurea var. fallax (Oehme) Rausch
• Echinopsis fallax var. shaferi,
• Lobivia fallax,
• Lobivia shaferi ssp. fallax,
• Echinopsis fallax,
• Pseudolobivia aurea var. fallax,

There are several varieties of L. aurea, with very different spine shapes and lengths.

 Lobivia aurea v fallax P137 La Rioja. Argentina
The spines are impressively strong and very showy. The spines of plants in cultivation are usually weaker, because many growers fail to give them full sun exposure.