there are many hundred species of mountain and rock plants which will thrive much better on an old wall, a ruin, a sunk fence, a sloping bank of stone, with earth behind, than they do in the most carefully prepared border, and therefore their culture may be fittingly considered here, particularly, as once established in such positions they increase and take care of themselves unaided. indeed, many an alpine plant which may have perished in its place in the garden, would thrive on any old wall near at hand, as, for example, the pretty pyrenean erinus, the silvery saxifrages of the alps, pinks like the cheddar pink, established on the walls[89] at oxford, many stonecrops and allied plants, the aubrietia and arabis.
a most interesting example of wall gardening is shown on the opposite page. in the gardens at great tew, in oxfordshire, this exquisite little alpine plant, which usually roots over the moist surface of stones, established itself high up on a wall in a small recess, where half a brick had been displaced. the illustration tells the rest. it is suggestive, as so many things are, of the numerous plants that may be grown on walls and such unpromising surfaces.
a mossy old wall, or an old ruin, would afford a position for many rock–plants which no specially prepared situation could rival; but even on well–preserved walls we can establish some little beauties, which year after year will abundantly repay for the slight trouble of planting or sowing them. those who have observed how dwarf plants grow on the tops of mountains, or on elevated stony ground, must have seen in what unpromising positions many flourish in perfect health—fine tufts sometimes springing from an[90] almost imperceptible chink in an arid rock or boulder. they are often stunted and diminutive in such places, but always more long–lived than when grown vigorously upon the ground. now, numbers of alpine plants perish if planted in the ordinary soil of our gardens, and many do so where much pains is taken to attend to their wants. this results from over–moisture at the root in winter, the plant being rendered more susceptible of injury by our moist green winters inducing it to make a lingering growth. but it is interesting and useful to know that, by placing many of these delicate plants where their roots can secure a comparatively dry and well–drained medium, they remain in perfect health. many plants from latitudes a little farther south than our own, and from alpine regions, may find on walls, rocks, and ruins, that dwarf, ripe, sturdy growth, stony firmness of root medium, and dryness in winter, which go to form the very conditions that will grow them in a climate entirely different from their own.
in many parts of the country it may be said with truth that opportunities for this phase of gardening do not exist; but in various districts, such as the wye and other valleys, there are miles of rock and rough wall–surface, where the scattering of a few pinches of arabis, aubrietia, erinus, acanthus, saxifrage, violas, stonecrops, and houseleeks, would give rise to a garden of rock blossoms that would need no care from the gardener. growing such splendid alpine plants as the true saxifraga longifolia of the pyrenees on the straight surface of a wall is quite practicable. i have seen the rarest and largest of the silvery section grown well on the face of a dry wall: therefore there need be no doubt as to growing the more common and hardy kinds.
[91]
a few seeds of the cheddar pink, for example, sown in a mossy or earthy chink, or even covered with a dust of fine soil, would soon take root, living for years in a dwarf and perfectly healthful state. the seedling roots vigorously into the chinks, and gets a hold which it rarely relaxes. a list of many of the plants which will grow on walls will be found among the selections near the end of the book.
