The fruit trees in a kitchen-garden should be all trained against the walls, and those trees which are grown as standards should be in a separate garden or orchard. The walls are best when about eight feet high, and they should have strong hooks or holdfasts built into them at the top, for the convenience of supporting a wooden coping, or of suspending mats or nets. Some persons recommend the walls to be built on arches; but this is a bad plan, as it is of importance to the gardener to confine the roots as much as possible to the border within the garden. The roots of fruit trees should never go deeply into the ground, as, if the roots are suffered to get so deep as to be out of the reach of the air, the trees will produce more leaves and branches than fruit. On this account care should be taken that the soil should not be more than eighteen inches deep; and the easiest and most effectual mode of doing this is, to dig out the border to the depth of two feet, and put a layer of brick-bats and other rubbish covered with gravel well rammed down to the depth of six inches, and to fill up the remaining eighteen inches with a fine rich mould. When a fruit tree border is in its proper state, the gardener should always be able to show the fibrous roots of his trees by removing a little of the earth with his hand. When the trees are planted the roots should be carefully spread out to their full extent, and care should be taken always to keep the collar of the plant above the earth, as when it is buried the tree is very liable to become cankered. As the blossoms of peaches, apricots, and nectarines appear early, they are very liable to be injured by spring frosts, and many plans have been devised for protecting them. All, however, are liable, more or less, to objection, as it is extremely difficult to put up mats without knocking off the blossoms. The best way is to have a deep wooden coping placed on the holdfasts that were let into the wall, with hooks in front, from which a curtain of bunting may be suspended, which should be kept up night and day during frosty weather; as there is quite as much danger from the sun during frosty weather, as from the frost. In fact, in most cases where plants are injured by frost, it is in consequence of a warm sunny day having succeeded a severely cold night.