Arequipa hempelii or Orocereus hempelii
(This plant comes in a 3.5" pot. You will receive a very similar plant to the one in the picture. It may or may not be blooming at the time of your purchase. The plant is shipped in its pot to prevent any damage to the roots).
Originally from the Mountains of South Peru, it is a short cylindrical cactus with dense short brown spines and bright purple/red flowers when mature.
Excellent as landscape or patio plant. It is suitable for small “desert” gardens, in association with other xerophytes. Where the open air cultivation is not possible due to the climate, it is to be cultivated in pot in order to shelter it in winter.
Recommended temperature zone: USDA: 8-10
Frost tolerance: Hardy to hardy to 10°F (-12°C) for short periods of time
Minimum avg. temperature: 50°F (10°C)
Sun exposure: Full sun to light shade
Origin: Andes mountains above 5000 feet (1500 m) in Peru and Chile
Growth habits: Clustering columnar cactus, up to 18" tall (45 cm)
Watering needs: Moderate water
Blooming habits: tubular red flowers in late winter to early spring. They are well liked by the hummingbirds.
Some of the information in this description has been found at desert-tropicals.com, llifle.com and cactus-art.biz