This section is from the book "Commercial Gardening Vol2", by John Weathers (the Editor). Also available from Amazon: Commercial Gardening, A Practical & Scientific Treatise For Market Gardeners.
For many years G. secunda and its variety glauca have been popular market plants, and are used extensively in connection with carpet bedding and for finishing up the edges of raised flower beds. Plants are usually sold in shallow boxes containing one, two, or three dozen, according to the size of the rosettes of fleshy leaves. During the summer months the tubular red and yellow flowers are borne on curved crozier-like stalks. Another useful species is C. metallica, which is a much larger and looser plant with fleshy spoon-shaped leaves of purplish metallic hue. In addition to these, other species used for summer work are agavoides, gibbiflora, ovata, Pachyphyta, bracteosa, pulverulenta, atropurpurea (or sanguinea), farinosa, Peacocki, etc. All these flourish in ordinary good garden soil in the open air from June till September or October, but must be protected in a greenhouse or frame during the winter. They are propagated by inserting the bases of the fleshy leaves and by detaching sprouts or suckers from the base of the main plant in sandy soil. If the tops are cut off and placed on soil they root and sucker freely in many cases, and sprouts spring out all round the decapitated stem if kept growing.