(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).
Trichocereus spachianus or Echinopsis spachiana is a a much decorative frost hardy cactus. It is a summer grower species that offers no cultivation difficulties. It can be overwintered outdoors if sheltered from rain and severe frosts.
Repotting: Repot in the spring, when their roots become cramped. Generally, they should be repotted every other year in order to provide fresh soil. After repotting, do not water for a week or more. Needs a large pot to accommodate a large root system.
Water: In summer, during the vegetative period, it must be regularly watered, but allowing the substratum to completely dry up before irrigating again (but do not overwater). In winter, it's to be kept dry. Preferable not to water on overcast days, humid days or cold winter days.
Hardiness: It is a quite frost resistant cactus, hardy to - 10° C (or less if very dry).
Exposure: Outside full sun or afternoon shade, inside needs bright light, and some direct sun.
Some of the information in this description has been found at desert-tropicals.com, llifle.com and cactus-art.biz