Walls
These are requisite for the proper cultivation of fruit-trees and numerous other subjects which require shelter and a warm situation; and the less favourable aspects which must of necessity be presented by one, or sometimes even both of the surfaces, may also be utilised for some purpose. In a kitchen garden the Walls serve as a boundary for the inclosure; and as, during sunshine, they accumulate a considerable amount of heat, which is given off when the air becomes cooled, most of the trees on southern aspects, at any rate, are in a warmer temperature even at night than they would be in the open ground. Amongst the principal fruits which in nearly every locality require Wall protection are Apricots, Figs, Nectarines, and Peaches. Morello and dessert Cherries, dessert Pears, and Plums, are also best, as a rule, on Walls; the Morello succeeds well in a north aspect, which is a great advantage.
The actual work of construction does not usually come within a gardener's province, but he has, not unfrequently, to propose the dimensions or give instructions how the work is to be executed. In a large garden, the Walls should be 10ft. to 12ft. high--the top of anything less than this would soon be reached by any of the fruit-trees named above. For a small garden, these heights might be too much for the inclosed area to be proportionate, and 8ft. would then be sufficient, but high Walls are always far superior to low ones. The materials commonly used are bricks (the dimensions of which are fairly uniform in all localities) and mortar. It is most important that garden Walls be substantially built, and the foundations made to rest on a solid bottom; the weight will, in course of time, cause settlements, if any portion of the ground is of a different character, and the base is, consequently, not of an equally solid description throughout. The foundations should be, at the base, quite double the width of the wall that they are intended to support. The proper thickness depends considerably on the height. Walls that are only to be carried 6ft. or 8ft. high may be constructed, if the material and workmanship are good, in 9in. work--that is, the length of one brick. Higher Walls than these should not be less than 14in. thick, while 18in. is much more substantial, and better in all ways. These dimensions are readily obtained by using bricks: 14in. allows the length of one and the width of another, and 18in. the length of two, for the total thickness. Walls are sometimes constructed with less solidity than this, and supported by occasional buttresses on one or both of the sides; these are objectionable unless really needed, because of their interference with the proper training of trees, and it may be pointed out that they swallow up a considerable quantity of bricks that would help to build a thicker and more substantial Wall, and one which would be more satisfactory in the long run. All kitchen-garden Walls should be provided with a coping projecting over from 2 1/2in. to 3in. on each side, and grooved beneath the under side of the projection for drip. Stone, if not too expensive, is the best material for copings; the entire part at the top should be slightly higher than the sides, so that water may pass off readily. For the protection of tender fruit-blossoms in s ring, when this is necessary, it is better to put up a temporary board coping from 6in. to 9in. wide, on brackets fixed to the Wall, than to make the permanent one too wide. This can easily be removed when no longer required; and if the edge of the board is placed beneath the stone, and the brackets are of triangular shape, there will be no danger of drip on the blossoms. Walls should always be kept in good repair: the holes caused by nailing in the mortar, and larger ones often caused by the action of frost, are invariably harbours for insects. Where insects are very numerous, as is often the case in old Walls, a dressing of fresh lime and sulphur, thickened with a little clay, and made a dark colour by the addition of sufficient soot, may be annually used, if desired. It should be applied during the time the trees are bare, when a little falling on them will seldom do any harm. See also Garden.