Читать книгу Trees and Shrubs for English Gardens - E. T. Cook - Страница 16

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If we were to take many books about trees and shrubs or general gardening as a guide, one might be led to think that only one way of increasing a tree or shrub existed, and that by grafting; but, as we have pointed out elsewhere, it is a mischievous practice when indiscriminately applied. It is not contended by this that grafting and budding are utterly needless, as in many instances these methods may be rightly adopted, but the four natural ways of increase are by layers, seeds, suckers, and cuttings. Many trees and shrubs are much better when grafted upon other stocks.

Of these, practise seed-raising whenever possible; but if seeds cannot be procured, then adopt other ways, and the man is wise who tries to keep a plant on its own roots. Neither budding nor grafting should be resorted to, unless other means fail absolutely. When standard trees cannot be got true from seed, budding or grafting must be practised, and the evils of these methods of propagation are not so pronounced in such cases as with dwarf plants. With the former, suckers, or growths from the stock, are easily seen as soon as they appear, but with dwarf plants a perfect forest of suckers may seriously weaken the plant before they are noticed.

Seeds.—These can be sown at almost any time, but the spring is the best, as those which germinate quickly have time to form strong young plants before the following winter. Some take two years to come up, and should be left in the ground. This refers more to seeds sown outdoors, and few hardy trees and shrubs require heat to assist germination. When sown in the open the beds should be made on a fairly rich, moist piece of ground, protected from cold winds, but fully exposed to the sun. After the seeds are sown, cover them with light tiffany shading, fir branches, or heather, but the first is best, as it is easily removed to attend to the bed. Conifers especially should be sown in beds, whether indoors or outdoors, as pot-culture results in the roots taking the shape of the pot, and never afterwards recovering from their cramped condition. It must be remembered, however, that varieties cannot be depended upon to come true from seed, though by careful selection for a few years many varieties will almost reproduce the characteristics of the parents. Hybrids, such as Berberis stenophylla, Hypericum moserianum, and many others, also do not come true from seed, so that cuttings, layers, or division of the old plants must be the practice chosen.

Suckers.—Plants which throw up suckers from the base, or below the ground-line, are easily propagated by detaching these suckers in winter with a portion of root. They will grow away readily, and soon form good trees or shrubs as the case may be.

Cuttings.—Nearly all the hardy shrubs, and a small proportion of hardy trees also, can be propagated by cuttings taken at certain times of the year. Summer cuttings are taken during the last two weeks of May and throughout June, the actual time depending on the season, and consist of the young shoots that have grown to a length of 3 to 6 inches. These should be pulled off with a "heel," and inserted in sandy soil in a close frame, with brisk bottom heat. The cuttings should be taken on a dull day, or early in the morning, and kept cool and moist until they are in the frame. A cutting that has flagged is useless, as it never revives. Deciduous flowering shrubs are usually propagated by summer cuttings, which generally root well in a fortnight or less. Autumn cuttings are taken during August and September, and are made from the partially ripened growths of the current year, inserted in sandy soil, in a close frame, without bottom heat. Winter cuttings are made from thoroughly ripened wood at any time between October and March, and are laid in rather thickly in rows outdoors, and only about an inch or less is left above the soil. The majority of our best flowering shrubs are easily increased in this way.

Layers.—Excellent trees and shrubs can be got by layers, and they may be laid down at any time of the year; they will be ready for removal in about eighteen months or two years.

Budding.—This is done about August, and the same rules apply to trees and shrubs as to Roses, &c.

Grafting.—This takes place outdoors from March to May, at the earlier time for deciduous trees and shrubs, and later on for evergreens. The actual time depends upon the season.

Where seed is not expressly mentioned below, it must be understood that this is the natural, and in many cases the best, way to propagate.

The following trees can only be raised from seed to do any good afterwards, though a few of them will throw up suckers, which can be taken off and replanted: Æsculus (Chestnut), Ailantus, Alnus (Alder), Arbutus, Betula (Birch), Carpinus (Hornbeam), Carya (Hickory), Castanea (Sweet Chestnut), Celtis (Nettle tree), Fagus (Beech), Fraxinus (Ash), Gleditschia (Honey Locust), Juglans (Walnut), Laburnum, Liquidambar, Morus (Mulberry), Prunus, Pyrus, Quercus (Oak), Sophora, Ulmus (Elm), and Zelkova. The varieties of any species of the above, and, in fact, of nearly all hardy trees, must be budded or grafted on the species they are forms of, but an exotic species should never be worked on the native representative of the genus—e.g. Æsculus flava should not be budded on the Common Horse Chestnut, as the latter is far too strong a stock for the smaller-growing Æsculus.

Acer (Maple) and Tilia (Lime or Linden) can be raised from seeds or by layering, the Lime especially being largely propagated from layers, which soon form strong young trees. The varieties of Maple are best worked on stocks of the species they belong to.

Cratægus (Thorn), Catalpa, and Robinia (Locust tree), can be raised from suckers or root-cuttings, if seeds cannot be got. Any of their varieties are usually budded or grafted on stocks of the parent species.

Ilex (Holly), Magnolia, Populus (Poplar), Platanus (Plane), and Salix (Willow). The Holly is easily raised from cuttings and layers, the second roots readily when layered, and the latter three are propagated in large quantities by winter cuttings. The White Poplar (Populus alba) is an exception, as this can only be increased by root-cuttings.