PLANTS FOR HEAVY FORMAL EFFECTS 143 



growing in tubs, as frequently seen, for accent points in a formal 

 garden or on a terrace, the amateur should best confine himself to the 

 Japanese laurel, the evergreen evonymus, the greenhouse hydrangea, 

 pyramidal arborvitae, and the boxwood. Most of these should be 

 transferred during the winter months, preferably to a cold cellar or 

 to a cold house, and even those which are semi-hardy, if left out of 

 doors, should be carefully boxed and protected. 



Perhaps the most interesting groups of trees and shrubs for formal 

 effects are those which are valuable for use in pleached allees. This 

 feature in the design of large estates has not yet reached its height and 

 will become more popular with the development of landscape design as 

 applied to American estates and gardens. The plants of this group 

 must Be resistant to disease and insect pests and they must be able to 

 thrive under conditions of severe pruning. The one most important 

 requisite is that they shall be long lived and not easily broken by win- 

 ter storms. The texture of branching must be close. To use for 

 pleached allees trees, such as the birches, which are short lived and which 

 always begin to deteriorate at a time when the allee should be most 

 picturesque and at its height, is landscape folly. It takes years, 

 five to eight years, to develop a pleached allee so that the tops will come 

 together. To endeavour to hasten the growth of plants by excessive 

 fertilization during the first two or three years will have a tendency to 

 split the bark and to expose the trunks to severe injury from freezing 

 and rotting. These plants should be of a spreading habit of growth as 

 contrasted 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 the 

 smaller specimens which will serve as fillers for the base. The normal 

 distance between rows on either side of a pleached allee is six feet to eight 

 feet. It is most advisable to train these plants to the pleached form 

 by 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. 



Trees and shrubs for open allees must meet the one requirement of 

 being close growing and columnar in their habit. An open allee may 

 be developed with rapid-growing material as well as with slow-grow- 

 ing material, and the time required is less than two-thirds as long as 

 the time required to develop a pleached allee of the same height. 

 Six to ten years may be required to develop an open allee eight to ten 

 feet in height. The scale of the allee, whether wide, with a tall border 



