WALL GARDENING.

Otago Daily Times, Issue 21148, 4 October 1930, Page 7

WALL GARDENING.

A SIMPLE MEANS OF GROWING ALPINES. The work of garden construction need not be left in its entirety till the autumn and winter months. Indeed, there is a good deal to be said in favour of doing much of it at this time of the year. The evenings are long and the busy amateur has more time to give to the laying out of the garden, while there are many plants which can be shifted quite safely if a little care is taken of them until they become reestablished. Particularly is this the case with alpines, which may almost invariably be purchased in small pots, and can, therefore, be planted with the minimum amount of root disturbance. Wall' gardening is coming more and more into vogue with the owners of small gardens,. Not only does it enable a very great variety of choice plants to be included in a space, but frequently, in the narrow confines of a villa garden, dry walls are much more in keeping with the environment than a more informal alpine garden. Because a certain number of plants, such as wall flowers and antirrhinums of <the commoner and coarser varieties, linaria erinus, and the wall rue may be seen clothing the face of apparently bare walls, that this is the ideal method of construction. It v is only a very limited number of subjects that are capable of dragging out an existance under 'such Spartan conditions, A dry wall to be an effective medium for the cultivation of choice alpines should either have a substantial core of good soil or else be used as a retaining wall to a terrace. In the small garden the former is usually the more practicable method, though wherever there is a severe fall in the land, advantage may well be, taken of it for terrace construction on a miniature scale.

Drainage is as important in the wall as the rock garden. In the case of double walls with a core of soil, the first essential is to excavate the site to a depth of a foot or more, and place in the bottom of this a deep layer of rough clinkers, brick ends, or other coarse ruhble. Special note should be taken of the manner in which the soil is rammed between the blocks of stone with a thick stick. It is of the utmost importance that there should be no hollow spaces anywhere; plants are absolutely unable to make satisfactory growth in loose, unevenly pressed soil, and much failure may be traced directly to this cause. _ Holes and crevices left in construction will*also form a harbour for slugs, snails, . mice, and other pests. The actual width of the central core of soil will depend a good deal on the height of the wall; the greater this is the more widely spaced should the two faces he. But it may be laid down as a general rule that plants should have at least two feet of good soil into which to root.

As the work proceeds the plants should be built into position. This is an infinitely better method than attempting to poke them into cracks and crevices after the work of construction isj complete. Such a mode of operation will inevitably result in tender roots being crushed and battered, and from this injury they must slowly recover before the plants can make any progress. ,If the work of building and planting proceeds simultaneously, the roots may be laid out quite naturally on a bed of fine soil, be covered with another layer of the same compost, and then have a stone placed in position to make them absolutely firm. Splendid results are obtainable in this way. The plants should, of course, be obtained in pots, as already mentioned, and must not be tipped out of these until required. Three points are of importance in the actual construction. First, the largest and heaviest stones should be. used at the base of the wall so as to form a substantial foundation. Secondly, each piece, as it is put in position, should be given a slight inward and downward slope, while the whole face of the wall should incline slightly backwards. This is technically known as a “ batter,” and serve the dual purpose of adding considerably to the strength of the structure, and also encouraging water to find its way between the stones to the roots of the plants. Thirdly, the stones should be placed in an irregular manner, and in such a way that the vertical crevices are not immediately super-imposed one upon the other. By this . means, a much 'greater binding effect is obtained.

In the case of high and rather narrow walls, it will be advisable .to provide some means of supplying moisture artificially. Quite an efficient method is to sink drain pipes vertically into the core of soil along the top of the wall at intervals of three or four feet. These may be filled with water nightly during hot weather and this will percolate to the roots.

The soil used for the core of dry walls should not be chosen haphazard. Alpines appreciate a free and open, but not dry, rooting medium. A mixture of loam, fibrous peat, well-rooted leafmould, and coarse river sand, using the last three ingredients in .about equal quantities, and a double portion of

loam, will suit the vast majority of rock plants. i

The stones themselves should also be of a porous nature. Hard quartz rock and blocks of unyielding granite are quite unsuitable for the purpose. They have a harsh, forbidding appearance in the garden, and do not provide a congenial surface over which the growing turfts may spread themselves. Limestone and sandstone are suitable materials. Much rubbish, from a builder’s yard may be turned to good account.

For the first few weeks after planting the alpines will require some artificial assistance in the way of moisture, especially should the weather be hot and dry. This is beat given by heavily syringing the plants every night. A great deal of moisture is taken in through the foliage, while a moist atmosphere is as essential to vigorous root action as damp soil. Nightly, syringing allows the plants several hours in which to take advantage of the supply. Almost any alpine may be grown in a well-constructed dry wall, though some are certainly better adapted to the purpose than others. Pew are more to be desired than the brilliant, but little seen, Zauschneria Californica. This somewhat forbidding name covers an altogether delightful Californian plant, with flaming orange-scarlet flowers, abundantly produced iu January and February, that never appears happier than when clothing a .sunny wall or bank. The stonecrops and houseleeks should be planted extensively, while rock pinks, in a multitude of species and varieties, will ensure a wealth of bloom during the early summer. Muchneeded blue and lavender shades may be provided by planting drifts of campanulas, of which C. portenschlagiana, C. garganica, W, H. Paine, C. carpatica, and the dainty C. pusilla, are amongst the best. Then the glorious Lithospermum prostratum, well-named Heavenly Blue, must have a place, bearing in mind that it cannot tolerate lime in great quantity. Yellow alyesum, the fleeting, but abundantly-produced blooms of helianthemum, aubrietias in many different shades;, and last, but by no means least, the noble silver saxifrages, are but a few more of the glorious alpine races which the wall gardener mrfy draw.—Plantsman.