A pergola might be described as a series of connected arches, were it not for the fact that many pergolas are flat.
There is nothing more beautiful in a garden than a well-made and well-covered pergola. If space and material permit of its being made 50 yards long or more, a great array of lovely Roses may be grown on it; but even if short it may be made exceedingly attractive.
Fig. 79. End Elevation Of Pergola
Although there is such a thing as a metal pergola, a wooden structure is far more ornamental. Rough stems of various thicknesses are desirable. The base of the uprights should be creosoted, tarred, or charred, and they should be inserted about 4 feet apart, but a variation either way is not essential so long as the structure is made thoroughly strong and steady. The same consideration governs the depth at which the posts are put in: 2 to 2 1/2 feet is about right.
A flat pergola is at least as expensive as an arched one, perhaps more so, because it is necessary to carry the posts, which are the most costly, up to a height of 8 feet If the pergola is arched, shorter and cheaper posts may be used, and the arches constructed of light, inexpensive material. The width must depend upon the wishes of the owner: 6 to 7 feet is very suitable.
Fig. 80. Side Elevation Of Pergola
Fig. 81. Ground Plan Of Pergola
Fig. 80 shows the side elevation of a pergola, with pots, boxes, or vases in the spaces (6) for the various plants employed. If, however, the pergola is to be covered entirely with Roses, they had better be planted out; and if a trenched, well-manured station is prepared for each success is assured
Fig. 79 shows the end elevation, and Fig. 81 the ground plan. In the latter a represents the posts, and b the boxes or vases, if such are employed.
If it is impossible to get stems and posts in sufficient quantity, a pergola may be constructed by setting ironmonger's wire arches 5 feet apart and bracing them with 1/4-inch parallel horizontal wires, one at the top, one at the centre, and one near the ground. Rigidity may be imparted to the structure by fixing uprights of gas-main pipes at every 6 feet. When well covered with growths this is not unsightly.