This section is from the book "Commercial Gardening Vol1", by John Weathers (the Editor). Also available from Amazon: Commercial Gardening, A Practical & Scientific Treatise For Market Gardeners.
A very large number of plants may be raised by means of cuttings of the stems or shoots. Soft-wooded or herbaceous cuttings having leaves are used in many cases, the shoots being in a half-ripened condition, that is, neither too young and sappy on the one hand nor too old, dry, and woody on the other. Such cuttings, according to the hardy or tender nature of the plant, are usually inserted in sandy or gritty soil, and most of the leaves are stripped off to check evaporation of moisture from the tissues through the stomata or breathing pores. One, two, three or more leaves are retained, according to the nature of the plant, so that a certain amount of assimilation may be carried on and induce a "callus" to develop over the base of the cutting. Once the callus is formed from the coagulated sap, roots are soon emitted, and the cutting then becomes an established and independent plant. As a rule, stem cuttings are cut immediately beneath a joint, because at that point the fibrovascular bundles containing starchy food matters are closer together, and the callus forms more quickly from the descending sap.
While the cuttings of some plants (e.g. shrubby Calceolarias, Pent-stemons, Snapdragons, Phloxes, etc.) root freely in cold frames, others require warmer and more genial surroundings, and must be placed in a hotbed or propagating frame with bottom heat. Indeed, even with hardy plants, the application of bottom heat will often induce cuttings to "strike" or root more readily than they would in cooler surroundings.
Fig. 61. - Sowing Fiddle.
In some cases (e.g. Heaths, Epacris) great care is exercised to encourage roots to develop. The pots or pans in which the cuttings are to be inserted are carefully drained with clean crocks to within an inch or so of the rim, and a compost consisting of 1 part peat and 3 parts silver sand is used for the cuttings. Glasses are placed over them for some weeks, to keep a moist atmosphere around them, and each day superfluous moisture is wiped from the glasses to prevent injurious dripping on the cuttings. The cuttings of such plants as Zonal Pelargoniums, Fuchsias, Calceolarias, Dahlias, Begonias (fig. 62), Phloxes, Pentstemons, Snapdragons, Carnations, Pinks, Lobelias, Aucubas, Roses, Heliotropes, Euonymus, Golden Privet, Skimmias, and many others root readily in any ordinary garden compost of a somewhat gritty nature if kept shaded from brilliant sunshine, and occasionally sprinkled overhead when there is a tendency for the air to become too dry.