How to Use Trees and Shrubs in the Garden
SHRUBS IN MIXED BORDERS
Where space in a garden is limited or where a greater interest and wider perspective is sought than would normally be provided by the traditional border of perennial herbaceous material, the mixed shrub border supplies answers to almost every problem. The shrubs themselves give an air of permanence and at the same time cut the amount of work involved. The herbaceous plants and thebring a wider range of shape, colour and texture to the scene. The herbaceous plants and some of the bulbs may need to be dug up, divided or replaced each year, but the shrubs need no attention other than a mulch around the roots and an occasional to keep the overall area under control and to allow the flower colour to be seen.
Choosing shrubs for a mixed border of this kind is not simple. The selection must be of those species and varieties that will not grow too large or too quickly, will provide flower colour to blend naturally with the surrounding herbaceous plants, will have a long flowering period or will fulfil a role by virtue of overall shape, colour, size or texture of the leaves.
It may be possible to buy certain container-grown shrubs from a garden centre which are more or less mature in size and this way the mixed border can spring ready-grown into existence. However, as a general rule, younger and less mature shrubs should be bought and planted and these sometimes fail to receive the attention they deserve in the mixed border. Because the total period of growth will be considerably extended, it is always helpful to use younger specimens. A further advantage of this operation is that planted young, the shrubs acclimatize themselves, settle down and grow well. If the borders appear somewhat sparse because of the immaturity of the shrubs, then it is a simple matter to fill the space which they will eventually occupy with some quick-growing hardy or half-hardy annuals or even to plunge into theof the bed some pot-grown plants such as pelargoniums and remove them again when the winter arrives. It is essential to leave correct space between shrubs in the initial planting rather than attempt to fill vacant space by planting them too closely together. This will only result in a border consisting of nothing but those shrubs.
A mixed shrub border can exploit the seasons, providing interest and colour at all times by the careful and tasteful selection of shrubby plants and herbaceous material which will develop and reach a peak according to a pre-planned pattern.
PLANTING SPECIMEN SUBJECTS
No more flattering situation for a tree can exist than in a smooth, green lawn — a specimen standing in the centre of a vacant stage, the target for the admiration of all eyes. This being so. It is obviously important that the tree or shrub should be chosen with care so that it is worthy of the attention it will receive.
Ask yourself a series of questions. Is the lawn large or small? Should the newly planted subject be in the centre, to one side? In the front or in the back? What sort of background will it receive? Will it be seen from the house? Will it be in the way of a path? Will it be an inconvenience when mowing? Should it be tall or spreading, evergreen or deciduous, green or other coloured, quite alone or with a little bed at its feet to hide the sometimes unattractive base?
When these and one or two more questions are answered you will already be halfway to choosing the right tree or shrub for the site. But do spend time and care on selection and bear the following points in mind. The subject chosen will last a decade, possibly the whole of your life or your period of residence in that house, so make sure you won’t become bored with it. Will it present an attractive appearance in summer and winter and preferably have some peak of appearance or performance to which you can look forward year after year? Remember that it will grow and what looks delightful and happily in proportion when young and immature may be inconvenient, even ugly when fully grown and occupying far too much space in the lawn.
Whether to choose a small tree, evergreen or deciduous, a low-growing shrub or a conifer will depend not only on personal taste but on area and surroundings. The following brief list of possible plants will serve as suggestions and an introduction to the wide choice.
Trees include: Betula pendula ‘Youngii’, weeping form of the silver birch, grows up to 3m (10ft); Parrotia persica, large green leaves which turn gold, orange and red. Grows up to 5m (16ft); Fagus sylvatica ‘Dawick’, slim, upright, gold leaves in autumn, up to 6m (19ft); Liriodendron tulipifera, the tulip tree, unusual shaped leaves gold in autumn, quick growing to 10m (33ft); Robinia pseudoacacia ‘Frisia’, bright yellow foliage, quick growing to 5m (16ft).
Shrubs: Carpenteria californica, evergreen with large white, grows to 2m (6ft); Cornus kousa chinensis, masses of white flowers and large leaves turning brown gold in autumn, 2m (6ft); Salix alba ‘Chermesina’, narrow, upright, with pale green leaves and scarlet stems in winter, 2m (6ft). Among the conifers, have a look at Chamaecyparis nootkatensis ‘Pendula’, Metasequoia glyptostroboides and Taxus baccata ‘Fastigiata’, all fascinating and much more beautiful than their names.
SCREENS AND WINDBREAKS
A hedge or a windbreak is more than a mere screen designed to divide one part of the garden from another or to provide dappled shade and a degree of privacy. A hedge is normally intended to keep people and animals out or in, and a windbreak must so stop, filter and subdue gales as to render them safe for plants and tolerable for humans. A double row of strong plants is essential for an effective barrier and these should grow from a deep and well-prepared trench. Stagger the plants and adhere to recommended planting distances.
There are many more types of hedges than are generally seen in most gardens. Many trees and shrubs can be adapted to make a barrier with a certain amount of pruning or clipping. Hedges can be low or tall, a light barrier or quite impenetrable. Flowering or foliage, and it depends on your choice as to which materials you use. Although it is wise to appreciate that some less well-knownmaterials may make excessive demands on the gardener or occupy too much space.
Subjects for traditional hedges, easily grown and managed. Include several conifers such as cupressocyparis, cupressus, pinus, thuja and yew. Other materials often used are quickthorn, Privet, green and purple beech, hornbeam, Myrobalan plum and the field maple, Acer campestre.
If you like the idea of a flowering hedge you can consider, choosing species roses rather than specimen tea or multi-flowered types. If you have space, rhododendrons make a good thick hedge, including the tough R. politician. Several of the berberis family make excellent and almost impenetrable hedges, their sharp spines fulfilling one function while their flowers, foliage or berries satisfy a taste for colour. One or two cotoneasters and pyracanthas also provide both flowers and berries, while the attractive and popular Primus pissardi ‘Nigra’ gives colour in the form of a deep purple foliage and masses of pink flowers each spring.
A good hedge is worth looking after, so ensure plenty of water at the roots in dry spells, give a light feed of general purpose fertilizer each spring, trim at least once a year, shaping to avoid accumulations of snow on top, if this is a problem. And for the first year or two keep weeds clear of the base.
Try to encourage growth at the base instead of at the top of the new hedge for the first year or two and do this by leaving the young shoots at the top and cutting back on those lower down. In many cases it is helpful to cut back the entire growth of a deciduous hedge to within 30cm (12in) of the ground soon after planting. This will encourage strong root growth and the development of a quantity of young shoots. A hornbeam or beech hedge should ideally not be pruned in any way for its first two years and hedges of practically all materials should be allowed to grow to their final required height before any trimming takes place at the top. Then aim to trim this a little slimmer than the width at the base.
SHRUBS AS GROUND COVER
The idea of planting low-growing shrubs to serve as a ground cover and cut out the chore of weeding is an attractive one and usually effective so long as the basic principles of ground-cover gardening are followed. It is essential to appreciate that ground-cover shrubs will not kill weeds already existing but will in time prevent weeds from growing under them. So, in the early days when shrubs are planted at say. 30cm (12in) intervals, the weeds will continue to grow for a year or two until the shrubs have grown and spread to cover the intervening spaces. Meanwhile the weeding will have to go on as before. Once the ground cover is established, it will not only suppress weeds but it will also prevent the sun from drying out the soil and heavy rain from scouring the site.
This being so, it is obviously helpful to use plants that will grow quickly and cover the ground thickly to suppress the weed growth. Perhaps the best subject for this purpose is ivy, available in several forms and colours. This produces many roots from its creeping stems and will soon make an impenetrable mat on the ground which will stop any normal weeds from growing through it. Similar to their speed of growth are the two periwinkles, lesser and greater, both of which bear small blue flowers in the spring. The well-known Rose of Sharon () is another flowering, low-growing plant which will quickly cover an area in need of weed control treatment with its mass of yellow flowers.
The subjects to be used as ground cover will depend to some extent on the site. The materials mentioned above would not be attractive if used on a large scale, for they would look monotonous and dull. They should be employed in smaller areas which they will quickly cover. On the other hand, a striking, interesting and attractive space of considerable size can result from the use of selected varieties of ericas or heathers. Some of these may demand an acid soil, but many will grow well and spread effectively in ordinary soils. Providing both flowers and foliage colour of remarkable depth and intensity, Ericas look particularly effective in weed-smothering beds when interspersed with dwarf and low-growing conifers in green, blue, gold or grey.
There are a number of low-growing shrubs that are successful and attractive as weed smotherers, but they are not all suitable to every type of soil and it is important to ask before ordering. Among these the following are to be recommended: Epimedium perralderianum, with glossy leaves and yellow flowers: Mahonia aquifolium. Also called Oregon grape, for its purple berries; several varieties of cotoneaster, with bee-filled flowers and glossy red berries and particularly effective and attractive in paved or semi-paved areas; and almost any of the perfumed and flowering thymes, which creep over the stones and subdue all weeds trying to grow in the spaces.
Where sufficient space is available, an informal woodland garden is a delightful feature. It is full of interest at all times of the year and once established it offers the gardener a charming way of merging the main formal garden with the surrounding countryside. A woodland setting is particularly effective when viewed in conjunction with water; either a small natural lake or an artificial pond or stream set up especially for this purpose.
Cultivars (cultivated varieties) and native trees and shrubs can be grown side by side. For those keen on conservation, native trees and shrubs only can be grown to create a sanctuary and habitat for many kinds of wildlife. If you have existing woodland, it may need to be thinned: tall and spreading trees should be well spaced if other plants are to thrive beneath them. You should also aim for some open spaces where shrubs can spread themselves to their full limits and where special specimens can be placed to their best visual advantage.
Ordinary soils can accommodate a rich variety, ranging from, say, early flowering pussy willows, spring and summer blossom, to the glowing berriedand the strawberry fruited arbutus which so brighten mid-winter clays. A good mixture of both evergreen and deciduous trees will thrive on acid soils to create a cover and a foil for brilliant azaleas and rhododendrons, camellias and other peat lovers. On limestone, beech, cherry, hawthorn, sorbus, larch and other conifers grow well and provide autumn hues.
The floor of the woodland can be closely carpeted with plants, shrubs, sub-shrubs such as periwinkle and herbaceous kinds, including those grown from bulbs. Ivies, which are extremely varied, are ideal for this purpose. The deep green leaved varieties will suit shady areas but the more colourful variegated ones should be given better light if they are to retain their colour. All of these will carpet as well as climb. The less shaded margins of the woodland and the borders of internal pathways can be planted with shrubs of varying height. The choice is almost limitless and can depend to a great extent upon your personal preferences. Shrubs and species of roses,, hydrangeas, choisya, , pieris, phlomis and erica are all good examples. Here also climbers can be trained up trees.
TREES AND SHRUBS IN CONTAINERS
It could be said that any plant which grows in the garden will also grow in a container, but in most cases this is only for a brief period and is dependent on the size of the plant and the container. At the same time this aspect of gardening presents opportunities too great to be ignored, for it means, for example, that in a garden composed of a limey soil it will still be possible to grow some of the lime-haters such as rhododendrons and azaleas by using a container filled with acid soil. It also means that a plant can be moved to suit the season, the occasion or even the whim of the moment.
The main problems encountered inare concerned with plant roots, for these are not only confined to a relatively small space but are completely divorced from the natural world, that great reservoir of soil of bottomless depth. Planted in the garden soil, any shrub during a hot, dry spell can send its roots far and wide and deep in search of moisture, but it cannot do this when planted in a container. It is therefore essential that container-grown plants should be watered thoroughly, sometimes as often as two or even three times a day. It is also vital that is adequate, for where the drainage holes of a container become blocked and it fills with water, the plant or plants it holds will drown. So always ensure that the drainage holes are adequate for the size of container and see that the bottom 6-8cm (2-3in) of the container holds broken crocks, pebbles or some similar material to ensure swift and efficient drainage. When watering by hand the supply of moisture should be sufficient each time so that the water seeps or trickles from the drainage holes. This throughput of water is sure to leach much of the plant foods from the soil, so replace this by regular feeding and by top dressing with fresh compost.
Because any trees or shrubs grown in containers are already given star treatment by being selected for this attention, it is most effective to choose subjects which are restrained rather than colourful, architectural rather than flamboyant. Fatsia japonica, for example, is an evergreen shrub with large, palmate leaves on long stalks and milky white flowers late in the year. Several varieties of the New Zealand flax, Phormium tenax, with upright, sword-like leaves of different colours, are eminently suitable for container culture. Convolvulus cneorum, another evergreen, with its foliage covered in silvery hairs and white flowers in late summer, is always interesting in a restrained kind of way. A number of conifers — green, grey, gold and blue — of dwarf-growing varieties, can look most effective growing in containers and if the containers are large enough, a whole miniature garden can be created. You can choose types that will live for years in a trough or sink yet never grow to more than a metre (3ft) or so in height.
The choice of container is another important consideration. Not only must it suit the needs of the tree or shrub, but it should also complement the surrounding architecture.
WALL AND CLIMBING SHRUBS
A good wall in the garden, whether high or low, particularly if it runs more or less north and south, can be of immense benefit, for it increases significantly the total area of the garden and it also permits the cultivation of certain plants, both ground growers and climbers, which would otherwise be impossible because of their lender nature. A south wall provides protection, attracts sun and gently releases absorbed warmth. A north wall gives protection and shade for more hardy or versatile plants.
Ground-growing plants can stand free of a wall and merely benefit from its protection, while others can lean against it and by means of its shelter climb up and along its face. You can also use low walls at the sides of steps or pathways for this purpose. Climbers can be divided into those that send out aerial roots which cling to the wall face and serve to pull up the new growth, those that cling by tendrils to any support provided such as trellis or support wires, and those that will climb only if tied in at regular intervals to supports of some kind. Even those climbers that attach themselves to a wall by means of aerial roots or sucker pads do little real harm to a sound wall and can be grown safely enough. Any damage is usually done by a vigorous climber such as a Virginia creeper or the rampant Russian vine Polygonum baldschuanicum that get their growing tips into cracks or crevices and then push their aggressive way in to enlarge the tiny space available. This allows in rain and frost so that in time the wall itself becomes damaged.
So long as a wary eye is kept on some climbers and over-enthusiasm curbed by cutting back too rampant growth, plants growing on or beside walls are relatively easy and certainly profitable to grow. But one or two elementary precautions must be taken. It will be noticed, for example, that the soil at the base of almost every wall is drier than that further away. This is due partly to the protection against rain given by the wall and partly to the fact that the wall’s stone or brick tends to absorb any moisture available at its base. For these reasons it is helpful, if possible, to plant the roots of a wall climber not directly at the base of the wall but a small distance away and let the climbing shoots lean over to the wall. In time of drought, pay special attention to wall climbers and give them additional water or a moisture-retentive mulch.
There is a tremendous range of materials for wall plants, ranging from roses, jasmine and honeysuckle through more utilitarian foliage climbers such as the invaluable ivies and the Virginia creeper with its brilliantly coloured leaves. There are productive grapes, quinces and even passion Bruit, climbers with flowers of every hue and trailing plants with delicate and romantic perfumes, including a clematis to twine around your bedroom window with the evocative common name of The Fragrant Virgin’s Bower’, or less romantically, Clematis flammula.