This section is from the book "The Gardener V3", 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 rage or fashion for fine-foliage plants, chiefly denizens of the plant-stove, which has existed for a number of years, has been the means of causing a great many of our finest greenhouse-plants, and particularly the hard-wooded section of them, to be elbowed almost out of cultivation. This state of matters may have arisen partly from the fact that what are generally termed "foliage-plants," whether of stove or greenhouse, are much easier of cultivation than the section of hard-wooded flowering-plants, and partly from the fact that the culture of foliage-plant3 has received an almost undue amount of prominence and encouragement from our horticultural societies, to the all but total exclusion of the greater proportion of, greenhouse-plants proper. Excepting such things as Azaleas and Heaths, it is very rarely that we see a well-grown specimen greenhouse-plant on our exhibition tables; while stove-plants, such as Crotons, Dracaenas, Palms, etc, are shown in numbers and varieties almost bewildering, a great many of the new varieties, indeed, being very slightly, if at all, different from many of the older varieties.
And the cry is, "Still they come !" Undoubtedly such plants are better adapted for house and table decoration than the general run of greenhouse-plants, and are available for this purpose at all seasons, whereas the others are not ; and while the fashion for such decorations continue, foliageplants will be largely grown for the purpose. Though I am particularly fond of the stove and its occupants, and would not like to part with them, still I think it a pity that greenhouse-plants should also not receive a larger share of attention than usually falls to their lot in the majority of places. If some of our leading horticultural societies would inaugurate the giving of prizes for this class of plants, no doubt plenty of cultivators would be ready to take them in hand.
In the following remarks, which are meant chiefly for young gardeners, it is intended to give just a few hints on the propagation and cultivation of some of the principal and most useful varieties of decorative greenhouse-plants. And first we may take the Azalea, as being one of the most useful as well as most highly decorative plants of the section. The Azalea is imported in such quantities from the Continent, grafted either as dwarfs or as standards, and is sold at such a very reasonable price by our nurserymen, that, unless by way of practice, it hardly pays to propagate them in private establishments. Should any wish to try their hand at it, however, one of the strong-growing common varieties', such as Fielder's White, should be selected from which to raise cuttings, as stocks on which to work the finer varieties. The cuttings may be rooted in a mixture of peat and sharp silver sand - 1 part of the former to 2 parts of the latter and they may either be pricked into a propagating-box where a brisk bottom-heat is maintained, or they may be put in a pot covered with a bell-glass, and plunged in a hotbed.
As soon as they are rooted pot them up singly in small pots, still using peat and silver sand, and replunge them in the bed for a time, till they take with the potting, after which they may be transferred to a warm house, and encouraged to make good healthy growths, and be well ripened, after which they may be kept cooler during the winter. Before grafting, the stocks had better be put into heat for a short time, so as to excite the sap into active circulation and when ready, head them over at the height you wish to graft; split the stock down half an inch or so with a sharp knife, and insert the scion, wedge-like, tie them well together, and cover with grafting-wax, and replace them into the propagating-box or hotbed keep them close and warm until the union be complete, after which they must be gradually inured to the light and air. Pinch the points out of the young shoots occasionally, so as to induce them to form good heads.
When ready for shifting into larger pots, the proportion of good fibry peat should be increased, and a few small pieces of charcoal may be added with advantage. Earn the soil hard about them at all future pottings; and for small plants the soil may be rubbed down pretty fine but for larger plants - say from those in 8-inch pots and upwards - the soil should be rather lumpy, being merely broken to pieces with the hands; and if good fibry loam is to be had, a little may be added, though it is not necessary. When they have done flowering they should be placed in a house with a temperature of about GO0 at night, till they make their growth, giving them a dewing night and morning with the syringe. When growth is made they should be gradually hardened off; and about the end of July they may be set out of doors, standing on a bed of ashes to keep out the worms. Stand them in a sheltered place, but exposed to the sun, so as to get the wood thoroughly ripened and buds formed. They may be again taken under cover early in October, placing them in a cool house. If they are wanted to bloom early, a few of those having the most prominent buds may be placed in a gentle heat, and gradually pushed forward - not too hard, however, at first.
Other batches of them may be introduced in the same way at intervals, in order to keep up a succession of bloom: while those intended for late flowering should be kept as cool as possible - a few degrees of frost even will not do them any injury. With judicious management as to forcing and retarding, a supply of bloom may be had the greater part of the year.
The great pest of Azaleas is thrips. This must be diligently looked after, and fumigated on the first symptoms of it appearing, repeating the operation two or three times, else they soon spoil the appearance of the plant, besides doing a great deal of injury. I habitually give them a syringing every few weeks during the growing season and while they are at rest, with soft-soap dissolved in warm water - a piece of soap about the size of a hen's egg to a large watering-potful of water. We lay the plants on their side, and dash it well into them and then in a few hours we syringe them in the same way with clear water. Besides keeping them clear of thrips, this also keeps the foliage clean and healthy. There are so many varieties of Azaleas in cultivation, and so many of them are good, that it is difficult to give a list of what all would consider the best. I may just enumerate a few of them, however, that are really good and will generally give satisfaction, merely giving the names, as colours can be found by consulting any catalogue.
Baronne de Vriere, Beaute Supreme, Dr David Moore, Due d'Aremberg, Duc de Nassau, Duke of Devonshire, John Gould Veitch, Le Flambeau, Queen of the Whites, Queen Victoria, Roi des Beiges, Roi des Blanches, Stella, Souvenir du Prince Albert, "William Bull, Princess Mary of Cambridge, Todmanii, Alice, Flag of Truce, and Model. J. G. W.