Miniature Gardens: Construction, Soil and Situation
HAVING chosen our container, ordered the plants and worked out a suitable design, we can now proceed with the more exciting business of actual construction. The first essential always is to provide adequate; a matter of vital importance to the majority of alpine plants, to whom stagnant water spells death. A large piece of broken flower-pot is placed over the drainage hole (or over each hole if there is more than one), and the bottom of the container is then completely covered with smaller crocks to about a quarter of its internal depth. The crocks should, of course, have their concave sides downwards, or they will hold the water instead of dispersing it.
In the larger type of miniature garden, built on the ground, still greater care is needed to ensure proper drainage, for the water cannot escape so easily as from a raised pan or sink. It goes without saying that the site chosen should not be in a hollow, and it is an advantage if the ground slopes downwards on one side. A position on top of a retaining wall or bank would be ideal for a garden of this description. If theon which it stands is light and porous, the drainage material may be placed directly on top of it, but on a heavy soil or badly drained site, further precautions are necessary. The soil should be excavated to a depth of several inches, and one or more soakaways dug to drain off the surplus water, after which the excavation is filled with crocks, brickbats or sharp clinkers.
From now onwards the procedure is the same for all three kinds of miniature garden. Over the drainage material a layer of ‘roughage’ should be spread for the purpose of preventing the soil from being washed down- wards amongst the crocks. The residue left in the sieve after coarse peat has been put through it serves the purpose admirably, and has the advantage of being sterile and free from the seeds of weeds. It is also usually available at this juncture, peat being a common ingredient of the composts we shall be using.
As to the compost itself, no hard-and-fast rule can be laid down, since different plants vary in their requirements. For the general run of alpines, however, a mixture consisting of 4 parts of good loam, 2 each of peat (or leaf-mould) and sharp sand, and 1 of coarse grit will be found quite satisfactory. The parts are measured by bulk, not by weight, as peat is very much lighter than the other ingredients. The best kind of loam is that obtained from a well-rotted turf stack, and the sand should be of the coarse-grained variety. Soft, binding sand is worse than useless. Suitable grit is easily made by smashing up some old flower-pots (which should first have been scrubbed clean) and passing the debris through a -1/2-in. sieve. As many alpines like lime and few resent it, this should be added either in the form of crushed mortar rubble or limestone chicken grit unless the collection is to include plants which are known lime-haters. It is better, however, to devote a separate enclosure to these, as their soil requirements are very different from the others. For these the proportions of peat and loam are reversed, and the grit is replaced by an extra part of sand.
Screes and Moraines
The beginner will not have progressed far in his study of books and catalogues devoted to alpine plants before he comes across the terms “scree” and “moraine.” Geologically speaking, these are two entirely different things, but in the garden they are both used to denote a bed or pocket consisting almost entirely of stone chippings with a very small quantity of added soil. In the open rock garden certain plants, whose natural habitat is the stony places in the mountains, thrive surprisingly well on this meagre diet, though even here they need copious supplies of water in dry weather. But in the pan or sink, with a depth of only a few inches, the scree mixture usually recommended dries out so quickly that unless you are prepared to keep it constantly watered the plants will soon die of thirst. For the miniature garden, therefore, I recommend a scree mixture of not more than 50% chippings, the remainder consisting of loam, peat (or leaf-mould) and sand in equal proportions. This prescription will be found very suitable for those plants which tend to forsake their compact habit when grown in ordinary alpine soil.
Preparing the Compost
Whatever kind of compost is used, it should be turned over and over on the potting bench until all the ingredients are thoroughly mixed; after which, if it is at all dry, it should be sprinkled with water from a rosed can and turned over again so that it becomes uniformly moist (but not soggy) throughout. It is then poured into the trough or other receptacle until the latter is filled to about half its depth. If rocks are to be used, it is better to place them in position at this stage rather than to fill the container to its brim and scoop out holes for them afterwards. The soil is then topped up to the required depth, tamping it down lightly during the process and taking care that the rocks are absolutely firm and immovable.
In the formal layout, of course, the surface is usually left flat, and the paths or other artificial features may now be added, after which the little garden is ready for planting. In the miniature rock garden undulations may be introduced to add variety to the scene, and if an extra depth of soil is needed for plants with long tap-
CONSTRUCTION, SOIL AND SITUATION roots it can be built up between the rocks, which should be so arranged as to form an upward extension of the sink or trough. If it is desired to grow plants in crevices between the stones, these should be firmly packed with soil, which may be kept in place by small flakes of stone wedged in suitable positions.
After planting, the rock garden should be top-dressed with stone chippings. These help to keep the soil moist, thereby reducing the amount of watering required, and, paradoxical though it sounds, they also keep the vulnerable necks of the plants dry in winter. In addition to this, they prevent thefrom being disfigured by soil-splash during rain or overhead watering, and they certainly give a pleasing finish to the little garden. Limestone chicken grit is as good as anything for this purpose, though rather light in colour until it has weathered. Granite chips, which are sold for the same purpose, can be used in conjunction with plants which dislike lime. In the formal type of garden, however, I prefer to dispense with chippings, which look rather out of place in .
Choosing the Site
In choosing the site for the miniature garden, due regard must be paid to the likes and dislikes of the plants we wish to grow. Alternatively, if the site is already fixed, the plants must be chosen accordingly. Nearly all true alpines enjoy full sunshine, so long as they are never allowed to become too parched for want of water. For these, therefore, a southerly aspect is the best. There are a few plants, however, which prefer some shelter from the fierce heat of the noonday sun, and others, chiefly the peat-loving shrubs, which demand still shadier conditions. The sites for these must therefore be selected accordingly, but it is not advisable to keep them in total shade, such as under a north wall. The dappled sunlight filtering through deciduous trees is ideal, so long as their branches do not actually overhang the little garden, which would quickly prove fatal to its inhabitants, owing to drip.
The smaller types of miniature garden are usually raised off the ground, where their plants can be seen and tended without the necessity for stooping. This also helps to preserve them from the depredations of slugs, which have an inordinate affection for certain alpines, particularly campanulas and dianthus. Staddle stones, which are sometimes used for supporting hayricks, make excellent and picturesque supports for pans and sinks, if you can get them. Failing these, it is a simple matter-to build suitable pillars of brick, stone or concrete, but they must be very firm and solid if they are to support sinks or troughs, the weight of which, when full, is considerable.