From the Greek kleistos, closed (thescarcely open) and cactus. Greenhouse perennial cacti (Cactaceae). Tall-growing cacti of the cereus group, mostly slender, many branched at times, with numerous ribs with closely set areoles and spines, flowers small with narrow tube. They are favourites with cactus collectors as they give height to groups.
Among fifteen species the following are likely to be found in cultivation. C. baumannii, upright growth, many yellow-brown spines, flowers orange-scarlet, narrow, western Argentina. C. smaragdiflorus, erect with long golden and brown spines, Uruguay. C. strausii, handsome white-spined and hairy plant, flowers red, small, can be grown as a house plant if given plenty of light, Bolivia.
These cacti are easy to grow in John Innes potting compost No. 1, to which is added a sixth part of sharp sand or grit. Pot in large enough containers to prevent the plants from falling over, and repot when the pot is too small or every three years. Water as often asdries out from March to September; keep dry in winter. Keep them in a sunny place in a temperature of 65-75 °F (18-24°C) in summer. 40 °F (4°C) in winter. Propagation is by seed sown as for most cacti, or by cuttings of side-shoots or by beheading the plant. The top, when the cut surface is dry, soon forms roots, and the old plant will make new shoots where it has been cut, to provide further cuttings.