This section is from the book "The Gardener V1", by William Thomson. Also available from Amazon: The New Organic Grower: A Master's Manual of Tools and Techniques for the Home and Market Gardener.
The Erythrina Crista-galli, or coral-tree, is one of the really neglected greenhouse plants : we cannot recollect having ever seen it cultivated except at two or three places; and why it should be so is hard to say, as it is a very handsome and striking plant when in flower, has beautiful foliage, is easily cultivated, and requires little room during winter, as it is then dried off, cut back, and may be put away along with Fuchsias and suchlike. It suits very well also for house work, though hardly adapted for the table, but it makes a grand exhibition plant when well grown.
There are several varieties of Erythrina, mostly from the East and West Indies, Brazil, and South America - the gum-lac of commerce being obtained from one of the species. The E. Crista-galli, however, is the best known, and, in fact, except in botanical collections, almost the only variety one meets with in general cultivation.
The Erythrina is propagated by cuttings, either of the ripened stems in autumn, cut into lengths, as is sometimes done in the case of Poinsettia pulcherrima, or of the young shoots in spring, after they have made about 2 inches of growth, taken off with a heel. In either case the cutting should be put into a properly drained pan, half filled with soil, and then filled up with sand. The cuttings, at any rate the young growths, should be covered with a bell-glass, and the pots plunged in a mild hotbed, or other place where a moderate bottom-heat can be obtained. As soon as they have made roots they should be potted off at once, and not delayed until the roots have got too long, else they may get broken off in the handling. The pots used may be about 3-inch ones, and the soil may consist of equal parts of loam and peat, with some old dried cow-dung added, and sufficient sand to keep it open. Until the young plants get established they should be kept in a temperature of about 60°, and syringed daily on fine days. As the season advances they may be removed to somewhat cooler quarters, and shifted into larger pots as they require it. They come into flower about June and continue flowering a considerable time.
After they are done flowering, and in order to get the wood properly ripened, they may be set in a sheltered position out of doors, and exposed to the sun, until the autumn, when they can be cut over and stored away for winter, where they will be safe from frost. They must be kept rather dry during this time, and started again in spring, according to the time they are wanted to flower. They are somewhat subject to the attacks of red-spider, which can be kept under by the use of the syringe. Thus treated, they will be found a welcome addition to our list of flowering greenhouse plants, and will well repay any care bestowed upon them.