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.
Many bulbous plants like Lilium bulbiferum and others produce seedlike bodies known as "bulbils" in the axils of the aerial leaves. These bulbils are capable of producing plants if sown in suitable soil and grown on for a year or two. (See fig. 24, p. 39).
In some Ferns, e.g. Asplenium bulbiferum, A. biforme, Woodwardia radicans, little plants also called "bulbils" appear on the fronds, and from these large numbers of plants may be raised quickly without having recourse to sowing spores. These bulbils may be regarded in the light of aerial offsets. (See fig. 46, p. 59).
FERNS (ASPLENIUM BULBIFERUM) GROWN FOR MARKET.
A very large number of herbaceous perennials, both hardy and tender, are more readily increased by splitting up or dividing the tufts into several portions, each containing a supply of roots. This operation is done either in the spring or in the autumn. If plants flower naturally during the spring and summer months they are usually best divided in the autumn; but if they flower in late summer and autumn they are generally best divided in the spring. Circumstances, however, may necessitate plants being divided at any season if it is desired to raise stock quickly without risking the life of the plants. Many plants that do not produce seeds or spores can only be propagated by division. Many Orchids, Ferns (e.g. Adi-antum Farleyense, and. Nephrolepis), and Bamboos are raised in this way, as it is the only one possible.
The art of budding consists in removing a bud from one plant and inserting it partly beneath the bark in another growing plant in such a way that it will obtain nourishment from its host, and eventually bear flowers or fruits. In the open air budding is generally practised from the end of July and during August, but may be done as late as September under abnormal circumstances, such as a particularly hot and dry season, when the sap may not flow freely until the weather becomes cooler, or until rain falls. Under glass, budding may be practised almost at any season when the buds and stocks are in a sufficiently advanced condition, but from January to March is the usual time. Only dicotyledonous plants can be budded or grafted, because they possess a cambium (see p. 36), and it is essential also that the bud or graft and the stock should be in the same family and closely related. Otherwise the difference in constitution and nature might be so great that union would be impossible. Thus Roses are budded on Brier or Manetti Rose stocks; Apples on Crab-apple, Paradise, Doucin, or free stocks; Pears on Pear or Quince stocks; Plums, Peaches, Nectarines, Apricots, Cherries on Plum stocks, and so on with other groups of plants (fig. 73).
Fig. 73. - Shoot of Apple arising from Bud inserted in Stock close to Ground Line, the Stock being cut back to form a stake to which young shoots are tied.
The bud or graft is really a kind of parasite. The plant that springs from it has no roots of its own. It is dependent upon the roots of the stock for the crude sap, which is pumped up into its stems and leaves from the soil. This crude sap, however, is elaborated in the leaves of the scion, and not in those of the stock; hence the changes are such that the leaves, flowers, and fruits exhibit the features and usually possess the nature of the scion and not of the stock, Laburnum adami being a notable exception.
There are several ways in which buds may be inserted, but the best and commonest method is that known as shield budding or ┬ budding (fig. 74). The dormant buds are taken from a ripened shoot of the current year's growth, each bud having a small piece of leaf stalk attached to serve as a handle. The stocks in which the buds are to be inserted in July and August should have been planted the previous October or November to get them well established by then. Buds are either inserted as low down the stem and as near the root as possible, or they may be inserted on the topmost shoots of a stock 3 to 10 ft. high. In either case a transverse slit is made with a sharp budding knife, and an upper cut about 1 in. long is made to meet it, the two cuts forming the letter T. The flat bone handle of the knife is gently pushed in the upper slit to open the bark, and render it easy to insert the bud, which has been severed in advance and placed between the lips while the slits were being made. In taking a bud the chief point is to select one that is dormant, and neither too young near the top of the shoot, nor too old or sprouting from near the base. If a flat piece of wood is taken off with the shield of bark it should be removed, care, however, being taken not to tear out the body of the bud with it. Some Continental and American budders do not trouble to detach the piece of wood, but in British gardens it is customary to do so. The bud being inserted, the bark is then tied round it with raffia or worsted thread, carefully but firmly, to exclude the air. In two or three weeks the bud will have united with the stock, and it will be necessary to cut the tying material. An expert budder will bud from 500 to 700 stocks per day, or more, with the assistance of an intelligent lad to clean the stocks and tie the buds after insertion.