From the Greek echinos, a hedgehog, and Cereus, referring to the very prickly nature of the plants (Cactaceae). Greenhouse cacti, first introduced in the late seventeenth century; a large genus with erect and spreading stems and mostly with large and spectacular.
E. berlandieri, thick sprawling stems with strong spines, flowers large, pink, Mexico. E. blanckii, stems sprawling, flowers purple, Mexico and Texas. E. dubius, stems yellowish-green, fleshy, flowers pink, south-east Texas. E. reichenbachii (syn. E. caespito-sus), stems stiff, erect, with numerous yellowish spines, flowers pinkish-purple, Mexico, Texas, E. rigidissimus, the popular rainbow cactus, stem erect, stout with many ribs closely covered with short spines, which are coloured reddish near the top of plant, flowers pink, Mexico and Arizona. Almost all shades of colour are to be found in this genus.
A suitable medium is an average potting compost, with a sixth part extra of grit, coarse sand and broken brick. Grow the plants on a sunny shelf in the greenhouse. Pot every two years for adult plants, every year for young seedling plants. Water the plants when the dries out from March to September, but give no water in winter. Temperatures should be 65-75 °F (18-24°C) in the growing period, 40 °F (4°C) in winter. Propagation is by seeds sown in a good seed compost in early spring; keep moist and at 70°F (21°C), shaded from direct sunshine. Several species with branching habit can be increased by taking sideshoots as cuttings. Dry them well and stand them on sharp sand to root.