The best example I have to show in my own garden is the so-called "Old Wall," before mentioned. It is the bounding and protecting fence of the Pæony ground on its northern side, and consists of a double dry wall with earth between. An old hedge bank that was to come away was not far off, within easy wheeling distance. So the wall was built up on each side, and as it grew, the earth from the hedge was barrowed in to fill up. A dry wall needs very little foundation; two thin courses underground are quite enough. The point of most structural importance is to keep the earth solidly trodden and rammed behind the stones of each course and throughout its bulk, and every two or three courses to lay some stones that are extra long front and back, to tie the wall well into the bank. A local sandstone is the walling material. In the pit it occurs in separate layers, with a few feet of hard sand between each. The lowest layer, sometimes thirty to forty feet down, is the best and thickest, but that is good building stone, and for dry walling we only want "tops" or "seconds," the later and younger formations of stone in the quarry. The very roughness and almost rotten state of much of this stone makes it all the more acceptable as nourishment and root-hold to the tiny plants that are to grow in its chinks, and that in a few months will change much of the rough rock-surface to green growth of delicate vegetation. Moreover, much of the soft sandy stone hardens by exposure to weather; and even if a stone or two crumbles right away in a few years' time, the rest will hold firmly, and the space left will make a little cave where some small fern will live happily.
The wall is planted as it is built with hardy Ferns—Blechnum, Polypody, Hartstongue, Adiantum, Ceterach, Asplenium, and Ruta muraria. The last three like lime, so a barrow of old mortar-rubbish is at hand, and the joint where they are to be planted has a layer of their favourite soil. Each course is laid fairly level as to its front top edge, stones of about the same thickness going in course by course. The earth backing is then carefully rammed into the spaces at the uneven backs of the stones, and a thin layer of earth over the whole course, where the mortar would have been in a built wall, gives both a "bed" for the next row of stones and soil for the plants that are to grow in the joints.
Jack. (See page [79].)
The "Old Wall."
The face of the wall slopes backward on both sides, so that its whole thickness of five feet at the bottom draws in to four feet at the top. All the stones are laid at a right angle to the plane of the inclination—that is to say, each stone tips a little down at the back, and its front edge, instead of being upright, faces a little upward. It follows that every drop of gentle rain that falls on either side of the wall is carried into the joints, following the backward and downward pitch of the stones, and then into the earth behind them.
The mass of earth in the middle of the wall gives abundant root-room for bushes, and is planted with bush Roses of three kinds, of which the largest mass is of Rosa lucida. Then there is a good stretch of Berberis; then Scotch Briars, and in one or two important places Junipers; then more Berberis, and Ribes, and the common Barberry, and neat bushes of Olearia Haastii.
The wall was built seven years ago, and is now completely clothed. It gives me a garden on the top and a garden on each side, and though its own actual height is only 4½ feet, yet the bushes on the top make it a sheltering hedge from seven to ten feet high. One small length of three or four yards of the top has been kept free of larger bushes, and is planted on its northern edge with a very neat and pretty dwarf kind of Lavender, while on the sunny side is a thriving patch of the hardy Cactus (Opuntia Raffinesquiana). Just here, in the narrow border at the foot of the wall, is a group of the beautiful Crinum Powelli, while a white Jasmine clothes the face of the wall right and left, and rambles into the Barberry bushes just beyond. It so happened that these things had been planted close together because the conditions of the place were likely to favour them, and not, as is my usual practice, with any intentional idea of harmonious grouping. I did not even remember that they all flower in July, and at nearly the same time; and one day seeing them all in bloom together, I was delighted to see the success of the chance arrangement, and how pretty it all was, for I should never have thought of grouping together pink and lavender, yellow and white.
The northern face of the wall, beginning at its eastern end, is planted thus: For a length of ten or twelve paces there are Ferns, Polypody and Hartstongue, and a few Adiantum nigrum, with here and there a Welsh Poppy. There is a clump of the wild Stitchwort that came by itself, and is so pretty that I leave it. At the foot of the wall are the same, but more of the Hartstongue; and here it grows best, for not only is the place cooler, but I gave it some loamy soil, which it loves. Farther along the Hartstongue gives place to the wild Iris (I. fœtidissima), a good long stretch of it. Nothing, to my mind, looks better than these two plants at the base of a wall on the cool side. In the upper part of the wall are various Ferns, and that interesting plant, Wall Pennywort (Cotyledon umbilicus). It is a native plant, but not found in this neighbourhood; I brought it from Cornwall, where it is so plentiful in the chinks of the granite stone-fences. It sows itself and grows afresh year after year, though I always fear to lose it in one of our dry summers. Next comes the common London Pride, which I think quite the most beautiful of the Saxifrages of this section. If it was a rare thing, what a fuss we should make about it! The place is a little dry for it, but all the same, it makes a handsome spreading tuft hanging over the face of the wall. When its pink cloud of bloom is at its best, I always think it the prettiest thing in the garden. Then there is the Yellow Everlasting (Gnaphalium orientale), a fine plant for the upper edge of the wall, and even better on the sunny side, and the white form of Campanula cæspitosa, with its crowd of delicate little white bells rising in June, from the neatest foliage of tender but lively green. Then follow deep-hanging curtains of Yellow Alyssum and of hybrid rock Pinks. The older plants of Alyssum are nearly worn out, but there are plenty of promising young seedlings in the lower joints.