Introduction to Gardening
The discovery that it is possible to have a bright and lively garden the year round comes as a delightful surprise to many people. For although bare dripping branches and a dark, windblown conifer may be pleasing to some, most people would prefer to have their spirits raised by a winter view of differing shapes, colours, and tints. Spring, summer, and autumn will readily produce succeeding pageants of colour, but with careful planting the garden will offer pleasing shapes and colours in winter as well. There is no need to have an off-season: even January can have a charm of its own if you plant with a winter wonderland in mind. Flowers will be few and delicate at that time, but if the setting is attractive you will be tempted outdoors to inspect them closely.
Although the most brilliant colours are generally provided by flowers, coloured foliage makes an important contribution to the scene. And because leaves, especially those of evergreen shrubs and trees, are with us far longer than any flowers, they should form a vital feature of your overall colour plans. (The term ‘evergreen’ is applied to any plant that has a full quota of foliage in winter and summer alike. We tend to think of evergreens in terms of a dark-green colour. In fact, they exhibit great variety: some are bright green; others have grey, blue, or yellow foliage -sometimes quite brilliant – which shines out in the dull winter days.)
The smaller the area of your garden, the greater is the need to look out for plants that offer more than one claim to attention. An obvious example is those that follow their flowering period with a colourful crop of fruits or berries. Others noted for their flowers may have especially attractive foliage that lasts all summer long. Where possible, different types of plants should be grown in association so that you get two or three lots of colour from the same area. Such happy groupings are discovered by observation and experiment – which is why visiting other gardens, private and public, can be so rewarding.
It is essential to get the mix right when selecting your plants. One way to ensure a garden of colour the year round would be to fill it with colourful conifers, but it would be terribly monotonous because it would offer very little variation between one season and another. In general it is better to restrict evergreens to about one in four of the trees and shrubs planted. The same principle applies to plants with bright-coloured, and especially variegated, leaves: attractive though these are, it’s always possible to have too much of a good thing.
Positioning is also most important, not only to ensure that the areas of colour are spread throughout the garden, and those that might clash are kept well apart, but also to place some winter flowerings, for instance, where they can be viewed from your windows.
Within this gardening category of this website, I describe some of the delightful plants that can help you create a garden that will be colourful throughout the year. None of those mentioned should be difficult to grow or hard to come by, although you may not find all of them at your local garden centre or nursery. Most are happy in ordinary garden soil; a few, however, flourish only in acid soil, and this is clearly indicated in each case.
Any perennial plant you buy is an investment, something that can pay dividends in the form of beauty and interest for many years, provided that the soil is well prepared, that you sow (or plant) it properly, and then give it such little aftercare as it may need. Remember that a plant’s roots may be as extensive as its top growth. While we can do all sorts of things for the part above ground, there is very little we can do for the roots once they are buried in the soil; hence the need for special care when planting. And if this seems to be rather time-consuming, remember that it has to be done only once for permanent plants. Even a whole hour spent giving a tree a good start in life is very little when you consider how many years of enjoyment you can expect from it.
Many people do not realise that roots need air to breathe in order to thrive. This is usually present in adequate amounts by the natural state of things, provided the soil does not become waterlogged. Where drainage is bad, water blocks the air spaces in the soil with the result that roots are killed by suffocation. On the other hand, as well as being well drained, the soil must be capable of holding sufficient moisture to sustain plants through long dry periods.
The major part of soil is made up of a mixture of mineral particles of varying sizes, ranging from stones and gravel, down through coarse and fine sand to silts, and finally to the smallest of all, the microscopic particles of clay. The soil behaves in different ways depending on which size of particle predominates. Gravelly and sandy soils tend to be light, free-draining, and therefore dry in summer, and they provide little in the way of plant food. At the other extreme, heavy clay soils are poor-draining, sticky, and difficult to work when wet, hold a great deal of moisture, and are potentially rich in plant foods. A good mixture of particle sizes results in what gardeners call a loam. This is neither so free-draining and dry as sandy soils, nor as heavy, wet, and poorly aerated as clay ones.
The mineral part of the soil holds water in the form of a surface layer of moisture around each particle, any surplus draining away through the gaps between them. The bigger the gaps are, the better the drainage and the easier it is for air to penetrate. If you imagine a jar of marbles compared with a jar of granulated sugar you will realise what a difference particle size makes to the gaps between them.
These gaps can be increased on heavy clay soils, so improving their drainage, if individual particles can be made to group together to form crumbs. The development of a crumb structure can be brought about by humus. This is a dark substance derived from the breakdown of organic matter, mainly plant and animal debris, and it forms the second major constituent of soil.
The natural supply of humus is reduced to very little on clean, cultivated land, especially in a tidy garden. Moreover, cultivation increases the supply of air to the soil and thus hastens the final disintegration of what humus there is. Gardeners therefore need to make good the supply by adding bulky organic material, such as farmyard manure, hop or mushroom manure, garden compost, or similar material.
Conversion of this organic material to humus is carried out by the unseen third constituent of fertile soil, its teeming population of micro-organisms. As a result of this process of decomposition, the organic material releases substances that plants use for food. The speed of the breaking-down process depends partly on the soil temperature and the amount of oxygen available. In poorly aerated, cooler clays it may take several years for a dressing of manure to disappear completely; in a hot, sandy soil it may vanish within a year.
Humus not only makes soil fertile; it also improves its structure. In free-draining sandy soils it holds moisture and foodstuffs at depths that are within reach of plant roots, while in heavy clays it improves drainage and makes them warmer and easier to work. There are various other methods of improving the structure of heavy soils. Horticultural gypsum improves clay soils by causing the particles to flocculate (group together). Hydrated lime sweetens the soil my making it less acid, and it also provides calcium, an important plant food. (Lime must not be used indiscriminately, however, because an excess may interfere with the ability of plants to absorb certain essential substances, especially iron.)
One of the greatest improvers of heavy clay soils is a natural one – frost. The microscopic clay particles are plate-like in shape and stick together after the manner of wet sheets of glass. By freezing and expanding the water, however, frost causes the particles to be pushed apart and upsets their alignment. A clay soil which is turned over in large clods in autumn and exposed to hard winter frosts can be broken down easily the following spring to create a tilth – a layer of fine soil -suitable for seed sowing. Walking on and so compressing such a soil when it is wet, however, quickly destroys this texture and can reduce it to the consistency of plasticine.
In general, plants that grow well on an alkaline (limy or chalky) soil will also flourish when planted in one that is slightly acid. But others, such as rhododendrons (including azaleas) and most heaths and heathers, that demand acid soil will not tolerate even a mildly alkaline one. Any hint of chalk or lime around their roots will upset them, and their leaves will turn yellow. The first step before choosing plants for a new garden must therefore be to determine whether the soil is acid or alkaline.
You can do this with one of the inexpensive soil-testing kits available at most garden centres. While excessive acidity is easily corrected by mixing lime with the soil (preferably in the autumn prior to spring plantings), it is extremely difficult to make an alkaline soil acid. Undoubtedly a moderately acid soil makes life much easier for anyone wanting to grow the widest variety of plants and is, of course, essential if your want to grow acid-loving ones.
Preparation for Planting
Armed with the result of the soil test, you can set about preparing the ground of your plot for planting. If it is a new garden, the first job is to clear away any surface rubbish and dig the whole area, turning over the ground to the full depth of a spade’s blade. At the same time organic material can be buried in the trenches, together with any weeds or grass skimmed from the soil surface as the work proceeds. Remove any old tree roots or rubble you may find. If you do this work in autumn or winter, leave the surface rough and open to weather until spring, when it can be broken down and levelled. If the work must be done in spring or summer and the plot is needed for immediate planting, the soil must be broken up finely with the aid of a fork when digging. (Alternatively you can hire a machine cultivator or use the services of a garden contractor.)
Refurbishing an existing garden is often bedevilled by the presence of perennial weeds. It is no use burying them or cutting them down as they will quickly reappear. If weeds such as couch grass, bindweed, and ground elder abound they should be killed with a herbicide before digging the soil. If it is necessary to dispose of any ailing shrubs or old trees to make room for new ones, remove as much of their roots as you can.
To ensure the new plants get away to a flying start, the soil should be enriched with plant foods 10 to 14 days before sowing or planting. The easiest method is to spread a general fertiliser over the area at the maximum rate recommended and mix it into the surface of the soil with a fork or tined cultivator. Follow this by treading over the whole area, shuffling up and down and across it, keeping your feet close together and your weight on your heels. Failure to refirm the ground in this way results in it being too well aerated, so that it will tend to dry out quickly.
The final stage of preparation is to level the surface by raking. Where plants are to go it is sufficient just to erase your footprints, but where you intend to sow seeds you must do a more thorough raking job. In order to grow satisfactorily, seeds must be in intimate contact with the soil so that they can absorb the moisture needed to trigger. What is required is a layer, about 25 mm (1 in) deep, of finely broken down soil from which all large stones and plant debris have been combed out. If the ground is lumpy you may need to tread and rake it several times to produce the required fine tilth.
Having the largest roots, trees and shrubs involve the most work in planting. Deciduous ones that have been lifted from the soil and sent out with bare roots from nurseries should be planted during their dormant period, which lasts from the time the leaves fall in autumn until about mid-March. Within this period, however, it is preferable to plant in autumn, before the ground becomes really cold. This will enable the plants to make some new root growth then, although they will of course remain leafless until the spring.
Before planting any tree or shrub, make sure that its roots are moist. If they appear to be dry, soak them in a bucket of water. Now check them for any damage and remove any broken or skinned root ends, cutting back to sound tissue. Extra-long roots can be shortened to match the others in length.
The technique of planting dormant trees and shrubs is shown in the drawings at left. Other perennial plants moved in winter should be planted in the same way, although it is better to firm in smaller plants with your knuckles or the trowel handle.
Pressing soil firmly into contact with roots is the essence of good planting. Plants will not root well into loose soil, which also (as we have seen) tends to dry out quickly.
Plants that have been grown in pots can be bought and planted out at any time. When the pot is removed, you will find that the roots are enclosed in a ball of soil. The top of this ball must finish level with or just below the surface of the ground soil, and the hole should be big enough to allow you to pack moist peat around the ball before filling in with soil. Again, make sure the soil is quite firm.
Bare-rooted plants usually manage to gather enough water from the soil to supply their moisture needs, except under very dry conditions. A pot-grown one, however, especially if it is in leaf, cannot do so – its entire root system is within the ball, which holds insufficient water to supply its needs for long. It is important, therefore, to water planted-out pot-grown plants until they have had time for their roots to grow and penetrate the soil around them. It is especially important to ensure the roots and soil are moist before planting out, so water the pots an hour or two beforehand. If it is exceptionally dry I find it best to stand the pots in a bucket of water for a little while to soak thoroughly.
Drying out of the surrounding soil just as the new roots are developing can cause a severe check to any young plant. For trees and shrubs, especially, it is wise to spread a layer of peat or compost over the ground around them as a mulch. This will reduce surface evaporation and so conserve moisture. A mulch 50 mm (2 in) deep or so will also smother germinating weed seedlings, an important consideration since weeds take both moisture and foods that developing plants need as well as physically smother small plants. The need to prevent competition is the reason why a circle of bare soil at least 600 mm (2 ft) across should be maintained around new shrubs and trees for the first few years, even when they are planted in a lawn.
Once they are established, healthy long-lived plants require regular but simple maintenance. Some trees and shrubs may need a little pruning to keep them shapely; others, such as hybrid tea roses, will need more rigorous pruning. You must, of course, inspect your plants frequently for signs of pests or diseases. Weeding, too, must be carried out regularly, although it will become less of a chore after a few seasons.