Several important points arise in connection with the selection and planting of shrubs. Shall evergreen or deciduous kinds predominate? Shall individual plants or groups of each kind be used? In what order shall they be set?
Deciduous shrubs should predominate where life and beauty rather than a mere screen are desired. Perhaps a proportion of two to one may be suggested. There will then be abundant life in spring and summer, with a suggestion of substance in winter. A border in which deciduous shrubs predominate is often rather ugly than otherwise in winter. It has an unkempt look. It suggests wildness, untidiness. The main cause of this is absence of culture. If the shrubs are properly pruned they will be clean and shapely. There will be plenty of young, brightly coloured wood, which will have a cheerful effect. Furthermore, kinds may be introduced which have boldly coloured stems. And colonies of cheerful bulbs, such as Scillas, Anemones, and Winter Aconites, may be planted among them.
The question whether individual plants or groups should be planted must turn to some extent upon the space available. The group system has the great advantage of giving bold, rich masses of colour. Groups of Rhododendrons, Azaleas, Berberises, Brooms, Hydrangeas, etc., have a noble effect. Certain plants, indeed, notably Azaleas, are apt to look ineffective when set singly. But the owner of a small garden cannot have the massed effects which are possible in large places, and would make a mistake to strain at them. He will do better to strive for good single specimens than to have crowded, ineffectual groups. One Rhododendron, or Weigela, or Berberis Darwinii, or Hydrangea, or Spiraea arguta - to mention at the moment only a few things that form beautiful isolated plants - will be more satisfying when well grown than a group of packed and meagre plants. Attention concentrated on these single plants - attention, I mean, in providing the right kind of soil, aspect, shelter and pruning - will be richly rewarded.
With respect to the order in which shrubs should be set, it may be advised that when the group system is adopted the face of the border should be deeply indented, so that a series of bays and promontories is formed. The richer, bolder things, such as Rhododendrons, Azaleas, Berberises and Brooms, may form large promontories; the more subdued kinds, such as Spiraeas, the bays. One may imagine a lawn stretching in front of a house, with an ebb and flow of shrub-grouping extending along both sides and the back of the lawn. With selected trees beyond, and a strictly limited provision of interesting objects on the lawn, such as specimen trees, shrubs, Pampas grass, Bamboos, and possibly a few flower beds, a beautiful effect would be produced.
In planting individual trees and shrubs it will probably be found best to work on the "opposite vacancy" principle. The shrubs are really planted in lines, but the components of each line do not face the components of the line behind, they face a vacant point midway between each pair. This is a common gardening plan in planting flower-beds and fruit bushes. It gives order without stiffness. And there must be system in the border. Let the amateur dump in his shrubs here, there and everywhere, and in a few years the shrubbery is a wild hotch-potch. In improving an unsatisfactory shrubbery I have often found that the simplest way of starting is to rearrange the shrubs on the "opposite vacancy" principle. Afterwards pruning and other cultural details come into play. To learn the system by the fireside, let the reader form a square with four pins and then set a fifth pin in the centre; he will then have a quincunx. By repeating the quincunxes he gets the system. He may, of course, retain it with a straight or a curved line of planting.
Ground that is to carry a considerable variety of trees and shrubs should be well drained. Areas that are swampy in a wet winter are liable to cause trouble. A piece of swampy ground can always be made an interesting feature of a garden, but it is not suitable for most shrubs and trees. It is rarely, however, that a piece of ground chosen for a house and garden is of such a character that it cannot be made suitable. If it were of the shape of a saucer, and water could not be got away, the gardener would form a pond or lake where the water naturally collected - at the middle of the saucer, the banked sides of which he would plant with shrubs. He would also plant the edges of the saucer. That, however, is an extreme case. Wet sites should certainly not be chosen for planting beds or borders of the principal ornamental shrubs until the under-water had been taken away from it by means of drain pipes.
The area of ground for beds and borders may range from six feet square upwards. But it is desirable to have freedom for working with reasonable boldness. Given a strip of border only six feet wide the planter will find himself handicapped. He can only plant small kinds. He will, in fact, have to do without all the great kinds, both deciduous and evergreen; and probably he would do well to restrict himself to small neat evergreens. With twelve feet before him he is in much better case. Here he can introduce small standard trees. Here he can get in a few fairly large kinds. And he can complete his quincunxes by planting three rows. If he is making a border which will have only one face he may put his trees and large shrubs towards the back; if a border to be seen from two sides then the larger things must go near the centre.
The preparation of the ground may well be thorough, particularly if light, in respect to the depth of working. If it is well broken up two spades deep and liberally manured it will carry not only the shrubs but also a ground work of bulbous and other flowers. I have already said, however, that I consider an abundant supply of moisture for the first year or two the most important item of culture, provided it is not stagnant under-water. Trenching and manuring, though good, are not vital, surface moisture is. Now surface moisture may be conserved by keeping the surface either carpeted with close-growing plants or else by maintaining a loose "crumb" of soil. Exposed soil should therefore be well dug at least once a year, and regularly hoed. After heavy summer rains a strong crop of weeds may be turned over with the digging fork.
It is prudent to keep shrub beds and borders under regular cultivation for more reasons than one. In going among shrubs to hoe in summer the gardener is reminded of the pruning. He sees the upspringing new shoots, that will flower the following year, crowded by the older wood which has recently gone out of bloom, and consequently he sees the necessity of pruning out the latter, in accordance with the instructions already given and amplified in Chapter 13.
We may devote a little consideration to shrubs and trees in relation to the paths. Near one or other of the side boundaries of a garden there is likely to be a path or road affording access to the kitchen, stables and garden outbuildings. In a large place this road - for road it will be - need not be screened on the outside, if there is park, meadow, or wood beyond it on the same property. But when it skirts another property the question of screening it on the outside may have to be considered. Here a belt of such cheap shrubs and trees as Laurels, Hollies, Aucubas, Larches, Poplars, Birches and Austrian Pines may be planted. The inner or garden side will also have to be screened, and here the hints already given will apply.
We may, however, go a little farther. In many gardens there are long inner paths - paths round lawns, paths along the face of shrubberies, paths leading to tennis lawns, Rose gardens or rockeries. Such paths may run for a considerable stretch between two sections of a lawn, or between a lawn and a shrubbery. In the former case, particularly, it is desirable to have objects of interest at intervals - a bed here, a specimen shrub or tree there, perhaps a group of Rose or Clematis pillars. These objects give variety and interest to the garden. Shrubs and trees may thus be used in relation to paths just as they may in relation to the house and the lawn.
There remains the water. Ground approaching water may be planted with things that love humidity - Bamboos, giant Rhubarb (Rheum paimatum tanghuticum), Meadowsweets, Phormium tenax, ferns, etc. The banks and island may be planted with Willows, Royal ferns, Reeds, drooping forms of Beech and other large trees, Dogwoods, Alders, Tamarisks, Elders, Bamboos, Gunnera manicata, Pampas Grass, etc.
The main points of water treatment are the planting of suitable approach groups, the clothing of banks with appropriate subjects, and the furnishing of islands with shrubs and trees that have a natural appearance at the waterside.
The popularity of modern hybrid Water Lilies leads flower-lovers to seize on any flow of water to form ponds, and even to devote considerable sums of money to making artificial pools. In the hot weather of summer these pools look beautiful when they are flashing under the sunlight. But their effect is enhanced when the banks are taken in hand and planted with groups of suitable shrubs, and with individual examples of Bamboos, Pampas Grass and other bold subjects; still more when islands are formed in the ponds and planted with pendulous trees.
A small stream may provide the water for such a pool. The soil excavated to make the bed of a pond will serve to form the islands. At a suitable place a rustic bridge may be built over the stream at a point near the pool.
The lover of Alpine flowers will doubtless do more than plant shrubs; he will form tiers of stone and plant colonies of rock plants. That, however, is another subject, and is dealt with in the companion volume, "Alpine Flowers and Rock Gardens."
It is in seeking to correlate his planting with the landscape that the garden-maker may find his most baffling problem. If the area to be planted is considerable he may be well advised to call in the services of an experienced landscape gardener, for the matter is one in which theory is inadequate. Nevertheless, natural good taste, aided by the illustrations in the present volume, will do much. Meantime, some suggestions as to arrangement may be given in another chapter.