Shrubs and trees that are to be kept in their pots through the summer should be plunged up to the rim of the pot, as this will save a good deal of watering. Plants that have been lifted and potted for a casual forcing may be planted out in May.
Two types of Azalea are largely forced: the so-called Ghent Azaleas and the varieties and hybrids of A. Mollis. The former are the little plants, with bare stems a foot or so high, and dense heads of bloom, which appear in florists' windows at mid-winter; they are prepared for forcing in millions by Belgian florists, and exported to nearly all parts of the world. They need only be brought into bloom in the way already advised, and they are so cheap that it is hardly worth while growing them after flowering. They are undeniably pretty, but they do not yield the beautiful salmon, orange, buff and fawn shades which are found in the Mollis type. Some of these are varieties of A. Mollis, but the best are hybrids between Mollis and pontic a or Mollis and sinensis. Oswald de Kerchove, salmon-pink; Floradora, orange; Anthony Koster, rich yellow; Prince of Orange, orange; Betsy de Brain, yellow-crested; Duchess of Portland, cream and rose; J. C. van Thol, orange; Alphonse Lavallée, orange; J. C. van Thol Imperial, flame colour; Glory of Boskoop, dep yellow; Clara Butt, rose flame; and Louis Endz, orange yellow, are examples. They force quite readily under the treatment indicated.
The double Japanese Cherries known botanically as Prunus Pseudocerasus and P. Pseudocerasus James H. Veitch have beautiful rosy flowers. Avium, the wild Gean, with single white flowers; Cerasus Rhexii flore pleno, double white; and serrulata, double white; are also beautiful members of the Cherry section of the great genus Prunus which force well. As regards the Peaches, Prunus Persica flore pleno, white; the crimson and rose forms, and the semi-double carmine form called Persica flore pleno magnifica, are all splendid. They bloom profusely with very gentle forcing, and the flowers are exquisite. Clara Meyer has already been mentioned and is equally good. Turning to Apricots, there are Prunus triloba, silvery rose, and its double form flore pleno.
Fig. Double Cherries And Peaches - Bloom Profusely With Very Gentle Forcing, And The Flowers Are Exquisite. Prunus Pseudocerasus Yoshino, a Japanese variety. Colour photo by R. A. Malby.
Pyrus floribunda, with rosy flowers, its double form, flore pleno, of the same colour, and the variety or hybrid Scheideckeri, blush changing to white, are all forced; the last, a lovely Crab Apple, that blooms profusely, is particularly good.
Two of the most beautiful white Magnolias are con-spicua and stellata, and both force well.
Cunningham's White is one of the best Rhododendrons for the purpose, but the magnificent Pink Pearl may also be used. The small dwarf blush-coloured species ciliatum and racemosum can be flowered in March.
Deutzia gracilis has long been a favourite for the purpose and other Deutzias may be used.
Of Spiraeas, arguta, prunifolia flore pleno and Thunbergii are excellent.
Hydrangea paniculata grandiflora is a splendid plant for forcing towards the end of winter.
Staphylea colchica, a very pretty white flowered shrub blooming in the ordinary way in spring, forces well.
There would be no trouble in adding considerably to the list of shrubs and trees suitable for forcing, but it is only desired to name the best. There are, of course, hundreds of subjects of shrubby habit which, coming from warm climates and not being hardy, have to be grown under glass in cold countries all the year round. But tender plants do not come within the scope of the present work.
The Japanese dwarf trees are a class apart. They are not tender, but they are grown in the greenhouse. They are hardy kinds, but they are not forced. What can be said of them but that they are "freak" trees, produced by a remarkable yet unnatural method of treatment? They are, of course, expensive, and can never enter into the real economy of a garden. But these trees have interest, alike as a tribute to human patience and skill, and as a proof of the wonderful adaptability of plants. There are trees in existence only a yard or so high at upwards of fifty years of age, which in nature rise to fifty feet high. And some of the dwarf trees are more than half a century old.
The Japanese habit of making miniature landscapes created a demand for the dwarf tree. When a complete garden is made in a space less than that of an average town back-yard, there is little room for trees of any kind, moreover, the methodical and correct Japanese make a point of maintaining proper proportions. In a landscape there must be trees. Where the garden is small the trees, to be in proportion, must be small also.
In course of time, these trees aroused the interest of European and American garden-lovers, and the astute Japanese developed a trade in the West. But garden-making in Britain and America is rarely on so restricted a scale as to make such material fitting in the open air. The trees, therefore, were not planted out, but grown in ornamental pots or other ware. As a rule, they are grown together in a large, cool, airy greenhouse. They form an item of interest under glass corresponding with a collection of clipped trees out of doors. They are not really gardening. They are "collecting."
Root restriction and branch twisting both play a part in forming the dwarf trees, but as no Western gardener is likely to practise it, there would be no advantage in devoting space to the matter.