This section is from the book "Handbook Of Hardy Trees, Shrubs, And Herbaceous Plants", by W. Botting Hemsley. Also available from Amazon: Handbook of hardy trees, shrubs, and herbaceous plants.
Layering is resorted to for those trees and shrubs that will readily root in this way, but which are not sure from independent slips or cuttings, such as the Elm, Lime, Laurustinus, Aucuba, Portugal Laurel, etc. This operation is very simple : the branches of the parent plant being bent down, partially severed, and fixed in the soil, where they will strike root in one or two years, according to the nature of the species. Many-shrubs and trees are readily raised from cuttings in the open ground in a partially shaded place. Such are Poplars, Willows, common Laurel, hardy Roses, Kibes species, Ivies, Privet, Virginian Creeper, etc., etc. The ground should be well prepared for cuttings, and if of a heavy nature, a little sand placed in immediately around the cuttings, care being taken to press the soil firmly against the cuttings, especially at the bottom. Most of the Coniferous shrubs will strike from cuttings, though nearly all of the arborescent species form handsomer specimens from seed; but a cold pit or greenhouse secured from frost in winter, and kept cool and shaded in summer, is necessary to raise them, as they are several months, or even more than a year, some of them, before they produce roots. Pots are preferable for this purpose, half filled with drainage, a layer of good free mould, and a layer of sand sufficiently thick ' (from one to two inches) that the heel of the cutting just reaches the mould. The whole must be very firm, and un-ceasing attention in watering is indispensable, for too little or too much are equally fatal. Cuttings of common Laurel and Box may be put in during the Autumn, but Ribes, Ivy, Climbing Roses, and most other subjects are better left till the end of Winter or beginning of Spring; and then, if sharp frosts follow, the cuttings should be pressed down again, as the frost often draws them out of the ground, or more or less raises them from their original position. Short-jointed, well-ripened wood should be chosen in all cases, as it produces roots more freely a.nd forms stronger plants in a shorter period. Cuttings of Roses, Kibes, etc., should be taken from shoots of the previous year's growth. From eight to twelve inches is a good length, and they should be inserted at least four inches in the ground; Laurel and Ivy cuttings are preferable with a heel or small portion of the older wood. The former should be from a foot to eighteen inches long, the tip being cut off to induce the lateral buds to shoot; but the latter are quite as well when only a joint or two remains above ground. For Coniferous plants very short lateral branehlets, with a heel or small portion of the older wood, are best. The leaves should be carefully, removed from the underground portion of all cuttings, and a sharp knife employed in preparing them.
Many shrubs and herbs may be propagated very rapidly by division, especially where, like the common Lilac, they throw up a multitude of suckers, or, like the Arabis albida, they produce running stems, or stolons. Plants with rhizomatous or bulbous roots increase by division in the former case, and offsets in the latter. But we shall enter more fully into this subject when speaking of the culture of herbaceous plants.
Excluding many garden varieties, which cannot be perpetuated by sexual propagation, Oaks, Maples, Ash, Horse-Chestnut, Sweet Chestnut, Whitethorn, Larch, Spruce, and other Conifers, besides a host of other things, including free-seeding herbaceous plants, are raised from seed.
Plants, as well as animals, are subject to a great variety of accidents and diseases, the ravages of parasites, of both the vegetable and animal kingdoms, and herbivorous animals; and in an artificial state more perhaps than when growing wild. The ill-effects of rapid and frequent fluctuations of temperature, unusually severe winters, late frosts, excess of rain or drought, storms and high winds, can only be guarded against to a certain extent. By choosing hardy species or protecting tender ones, efficient drainage, watering, and providing the supports required by different plants in good time, a great deal of the mischief likely to ensue from these causes may be avoided. Birds may enjoy perfect immunity in the ornamental garden; for here, whilst doing a great deal of good by clearing off destructive insects, they effect little harm, and afford, moreover, a great deal of pleasure to most people. The greatest scourges of the animal kingdom belonging to the larger class are rabbits and hares, rats and mice. The latter are very mischievous among seeds, and in winter they will destroy rare herbaceous plants by nibbling them away, so there is nothing for it but to trap them. Moles occasionally, but not often, get into the flower garden, whence they must be banished with all speed. Rabbits and hares are easily excluded by the use of wire netting made for this purpose. Wasps, hornets, and ants are all undesirable, more on account of their painful stings than anything else. Ants may be destroyed by pouring boiling water into their nests, or where this is impracticable from the vicinity of plants, inverted dishes smeared with honey will trap them. Wasps and hornets are usually suffocated in their nests at night by blowing the fumes of rags dipped in brimstone into their holes. But it is when we come to such pests as snails, slugs, caterpillars, grubs and lice, or green fly, that we meet with our worst enemies. The only effectual way of getting rid of snails, slugs, wire-worms, and grubs, is to hunt them out and kill them outright; but lice and caterpillars and other parasitical insects may be kept under pretty well by syringing the plants attacked with tobacco-water, or a solution of some of the compounds manufactured for this purpose. Birds aid materially in diminishing the number of these injurious insects. Wasps and ants, but notably the different species of Ladybird (Coccinella) consume myriads of the green fly. The Lime, amongst trees, is especially liable to the ravages of caterpillars, but nearly all deciduous trees and herbs are subject to the attacks of different species. In the case of large trees, it is usually left to the birds to destroy them; but much may be done to stay the ravages, particularly of those species infesting Conifers that deposit their larvae in large nests, by cutting off the small branches and burning them. Amongst reptiles, lizards and toads may be considered as the most useful, as they subsist entirely upon insects and slugs. And gold-fish not only add to the attractions of a lake or aquarium, but also serve to purify the stagnant water.