CHAPTER XXXVII

PLEACHED OR GREEN ALLEYS

In the old days the pleached alley was as familiar in English gardens as the pergola of the present age. Both are interesting, and both provide grateful shadowed walks in the heat of summer. The trees most generally used in the fashioning of pleached alleys were the Hornbeam and Lime, both native of this country, but green alleys have been made of Yew, of _Cotoneaster buxifolia_, of Holly, and other evergreens. There are flowering Cherries of weeping habit that would suit well for such treatment, and several other small trees of pendulous growth, such as Laburnum, Weeping Ash, and the large-leaved Weeping Elm. There is an important green alley at West Dean, near Chichester, of Laburnum only.

The green alley differs from the pergola in that the pergola has solid and permanent supports, its original purpose, in addition to the giving of shade, being to support vines. The green alley, being made of stiffer and more woody growths, only needs a temporary framework to which to train the trees till they have filled the space and formed the shape. Hornbeam was the tree most used in former ages, and for a simple green alley nothing is better. Beech is also good. Several other of the smaller trees of weeping growth should be more used for this and the allied uses of training for arbours and other shelter-places in the garden.

The common Plane is much used on the continent for green shelters; the trees are pollarded at about eight feet high, and the vigorous young growths trained down horizontally to a slight framework.

It would be interesting to make a green alley with two or perhaps three kinds of plants whose leaf form was of the same structure. For instance, a groundwork of Weeping Ash could soon be trained into shape, and Wistaria would be best to grow all over and through it. The more stiff and woody Ash would supply the eventual solid framework, as by the time the Wistaria was making strong growth (for it is very slow to make a beginning) the whole would be well in shape, and might dispense with the framing of "carpenters' work" that is necessary for its first shaping. It would be best to plant the Ash zigzag across the path so that the main of the head of each tree might be trained across the path and down to the ground on the opposite side, when it would occupy the space between the two opposite trees.

It is important to further maintain the distinction between green alley and pergola by using in the green alley only things of a permanent and woody character; no Roses or Clematis, or any other plants of which portions are apt to die or wear out. These are proper to the pergola, whose permanent substructure makes it easier to cut away and renew those of its coverings, whether structural or growing, that are liable to partial decay.

A great many delightful things may be done with these green alleys and green shelters. Much interest is already aroused in the pergola, and when thinking of this it is well to consider these other ways of adding to the comfort and charm of our gardens. One thing, however, should be carefully considered. It should be remembered that where a path is made more important by passing under trained green growths it should have some definite reason for being so accentuated, certainly at one and desirably at both ends. It often occurs that in laying out ground the owner wishes to have a pergola, as it were, in the air, and when there is nothing to justify its presence. It should not be put at haphazard over any part of the garden walk. If of any length, it should distinctly lead from somewhere to somewhere of importance in the garden design, and should, at least at one end, finish in some distinct full-stop, such as a well-designed summer-house or tea-house.

Another important matter is that a pergola or green alley, in the usual sense, should never wind or go uphill. It is not intended by this that shading coverings cannot be used in such places, but that they would want especial design, and it is altogether a matter of doubt if these could not be much better treated in other ways.

The circumstances of different gardens are so infinitely various that it is impossible to lay down hard rules; only general rules can be given and exceptional circumstances dealt with by exceptional treatment.

Green alleys require some attention. In winter the oldest of the wood must be cut out to make room for the young growth, and when this is lengthening vigorously it must be carefully laid in.

If the alley has an iron framework, which is necessary when such strong growing things as Wistaria are used, this may be clothed during the first few years, until the Wistaria is growing strongly, with annual climbers such as _Cobæa scandens_, _lophospermum_, _Mina lobata_, and even varieties of the large-flowered Clematis, which must be removed when the Wistaria covers the alley.

Very charming alleys are sometimes formed of fruit trees--Pear, Apple, Cherry, and Plum making delightful spring pictures, and almost as much so when in fruit in autumn. Where fruit and flower are desired every shoot must be exposed to sun and air. When densely shaded by other growths the wood does not ripen, and therefore flowers badly, if at all.