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growing in tubs, as frequently seen, for accent points in a formalgarden or on a terrace, the amateur should best confine himself to theJapanese laurel, the evergreen evonymus, the greenhouse hydrangea,pyramidal arborvitae, and the boxwood. Most of these should betransferred during the winter months, preferably to a cold cellar orto a cold house, and even those which are semi-hardy, if left out ofdoors, should be carefully boxed and protected. Perhaps the most interesting groups of trees and shrubs for formaleffects are those which are valuable for use in pleached allees. Thisfeature in the design of large estates has not yet reached its height andwill become more popular with the development of landscape design asapplied to American estates and gardens. The plants of this groupmust be resistant to disease and insect pests and they must be able tothrive under conditions of severe pruning. The one most importantrequisite is that they shall be long lived and not easily broken by win-ter storms. The texture of branching must be close. To use forpleached allees trees, such as the birches, which are short lived and whichalways begin to deteriorate at a time when the allee should be mostpicturesque and at its height, is landscape folly. It takes years,five to eight years, to develop a pleached allee so that the tops will cometogether. To endeavour to hasten the growth of plants by excessivefertilization during the first two or three years will have a tendency tosplit the bark and to expose the trunks to severe injury from freezingand rotting. These plants should be of a spreading habit of growth ascontrasted with the columnar habit of growth desired for open allees.While these specimens are planted at intervals of eighteen to twenty-four inches in rows, it often becomes necessary to interplant with thesmaller specimens which will serve as fillers for the base. The normaldistance between rows on either side of a pleached allee is six feet to eightfeet. It is most advisable to train these plants to the pleached formby the use of iron pipe and wire. This can be done by a skilled gar-dener, by constant attention and the frequent use of pruning shears. |
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