Cereus is a genus of succulent plants for the greenhouse. In most species, the flowers are large and often fragrant.
C.chalybaeus grows 10 feet tall and has red flowers which are white on the inside. C.horridus is taller at between 15 and 20 feet and produce greenish-red flowers.
When potting, use a compost which is a sixth part coarse sand and grit. They should be watered between March and October but given no water in the winter. They should be repotted every two to three years when the plant outgrows the pot.