DESIGNING A GARDEN POND

DESIGNING A GARDEN POND

A good landscape gardener and a good photographer have much in common. Just as a good photographer knows exactly how to compose his shot before taking it, so a good landscape gardener should have a clear idea of what he wants before starting work on the site. Con-siderable experience is required in order to visualize precisely how any particular design may look in practice. Few amateur gardeners — and by no means all professionals — can accurately conceive a project entirely on paper or in their heads. Most gardeners will modify their initial scheme as it progresses. Nevertheless, the more clearly you can visualize and plan your water garden in advance the more satisfactory will be the result.

You should begin by deciding which type of water scheme best suits your needs: a patio water garden; a formal pond with or without other forms of gardening and with or without fountains and waterfalls, or an informal pond with or without embellishments.

The patio pond

If you live in an inner city environment with no more than a small but sunny patch of ground for a garden, then a patio water garden might well be the answer. A tatty patch of lawn with one or two meagre shrubs can hardly be regarded as a garden at all; but a patio and pool can, and with no more main-tenance, indeed less, than that required of a lawn of the same area. Moreover, a pond, no matter how small, is a legitimate focal point in a way that a rose bush is not. If you doubt this, consider the suggestion: ‘Let’s have lunch round the rose bush.’ Nothing sounds more odd, and nothing more natural than: ‘Let’s have lunch round the pond.’ Countless thousands of backyards, too small and ugly for conventional gardening, could be trans-formed by making them into patio water gardens.

If you are a person who is away from home for long periods, who only sees the garden at weekends, who likes neither weeding nor mowing the lawn, a patio water garden offers the ideal solution. The same is true if you happen to be the fortunate owner of a pied-a-terre away in the country or in some foreign land. A patio water garden can still look fresh and attractive after long periods of neglect. Finally, a patio and pond offer op-portunities to anyone who owns a roof garden, which is usually limited to potted shrubs. For the owner of a large garden, a patio pond is likely to be regarded as no more than an optional extra. No one would want to convert a whole area of rolling lawns and well laid out borders into paving stones and water. The most popular idea in such cases is to combine the patio with the back wall of the house, the pond perhaps being visible from the house through French windows (but not so close to the windows that one steps straight out of the house into the pond!). Wherever the patio is situated, so far as a large garden is concerned, it should be combined with some other feature of the garden — if not the back of the house, then a hedge or a wall. A patio, alone, in the middle of a garden of any size will look stark and out of place.

Patio ponds are usually formal in design. A formal, regular shape nearly always harmonizes best with the strong, clear shapes of paving stones or bricks. But a pond should never be square. For some strange reason, a square always appears dull, even deadening (which presumably accounts for that piece of American slang: ‘He’s a square’). Make your pool rectangular; and if you have sufficient space, you might have one large rectangle bordered at each corner by a smaller one. Or the pond might consist of two interlocking rectangles. There is no limit to the number of geometric designs one can envisage. But do not make the pond too complicated or fussy. One soon becomes irritated with a fussy design. And above all, do not make your pond so broad or long that you cannot walk the whole way round it with plenty of space to spare. Quite apart from the fact that every visitor under the age of eleven will be certain to fall into the pond or make a good attempt at doing so, you want to give the patio a sense of spaciousness. The patio should never appear to have been squeezed in, as an afterthought, between the pond and the surrounding wall. The smaller the patio, the smaller should be the pond in proportion to it. Rarely should the length and width of the pond exceed one third of the length and width of the patio.

This is even more important if you decide upon a raised pond. If your space is limited, a raised pond will tend to make the area appear even more confined. On the other hand, if your patio is surrounded by wrought iron work or a light railing, as is the case with many roof and terrace gardens, a raised pond will help create a welcome sense of solidity. And it does have the advantage of bringing the plants and livestock closer to view. (Having a broad coping stone on the wall makes an excellent seat.) Flexible liners can be used for raised ponds just as well asconcrete. The liner simply needs to be held in place by being cemented between the last line of bricks and the coping stone.

When levelling the patio area it will also be necessary to take into account the thickness of the paving units. To do this, mark the thickness of the unit on the ends of a series of wooden pegs. Drive one of the pegs into the ground so that the top of it is flush with the earth surrounding the patio area. The ground should then be whittled away until the mark appears. Using a straight board and a level, the remaining pegs can be driven in at intervals so that they are level with the first. The soil is then removed to the depth of the mark on all the pegs. Finally, remove the pegs and again check on the level of the ground.

If you are using paving units which are regular in shape, then the length and width of the patio and of the pond must be multiples of the measurements of one such unit. For example, let us say that one paving slab measures 75 x 90 cm. Then the width of the pond should be a multiple of 75, and the length a multiple of 90. For example, if it were planned that two paving slabs should match the length and width of the pond, then the pond would have to measure 2 x 75 cm. By 2 x 90 cm. i.e. 1.5 x 1.8 metres. On the basis that the patio should not be less than three times as long and as wide as the pond, it must measure at least 4.5 x 5.4 metres. So for this patio 32 paving slabs are required: (24.3 — 2.7) -4-0.675 (i.e. the total area of the patio minus the area for the pond, divided by the area of one paving unit).

When a large number of small paving units is involved, it may be necessary to take into account the width of the joints, and modify the dimensions of the pond accordingly. However, this is not usually necessary with small patios as the width of the joints can be taken up by a slight overhang of the units immediately surrounding the pond. (To standardize the width of the joints, a couple of wooden pegs — about 13 mm. Thick — can be placed temporarily between the units.)

There is little difficulty about using large paving slabs. But laying down a complicated pattern needs a great deal of forethought and measurements have to be exactly right. And it becomes more difficult when the paving units are of more than one kind or colour. There is a useful moral in the cartoon of the little man laying down black and white tiles in a baronial hall. He comes to the last space and then discovers that whether it be a black or white tile that he puts down, he is going to have two tiles of the same colour side by side. It is not a bad idea to lay out the pattern be-fore excavating the pond. This way you can be certain that the dimensions of the pond fit the pattern.

Concrete slabs can be safely laid on sand, or set in mortar. The slabs round the pond, no matter how immovable they may seem, are best set in mortar. Make sure the earth is very firmly tamped down before laying the slabs, and add coarse aggregate if necessary. Small paving elements, such as cobbles, tiles and bricks should be set in mortar. It is often more satisfactory to prepare a solid concrete foundation 50-60 mm. Thick, prior to bedding down the paving elements on mortar. Due allowance must be made for the depth of the paving element, the mortar and concrete foundation. And if the patio is bordered by a lawn, sink the paving elements by an additional 15 mm. In order to facilitate cutting of the grass. The mortar can be made by mixing one part of cement with three of sand. Be sparing with the water. Spread the mortar to a thickness of about 25 mm. (50 mm. In the case of sand), lay down the paving stone and lightly tap into position. Any mortar that gets on the surface of the paving slabs should be wiped off immediately to prevent staining. The joints can be filled later with mortar or sand, depending upon which you have used for the foundation. You might find a dry-mix mortar speeds up this operation. Fill the joints with the cement and sand mix, then, very lightly, add the water. The risk of staining the patio is reduced with this method.

Irregular stone is by far the easiest kind of paving to lay. The only point to remember is that all the large pieces should not be clumped together in one part of the patio and all the smaller ones in another. This can happen if you do not start off with the firm idea of mixing all sizes together. If you want an informal pond, then ‘crazy paving’or irregular stone is the obvious material to use, and will look well in almost any scheme.

Glazed tiles and to a lesser extent smoothfaced bricks will tend to give your patio garden an atmosphere of coolness. In warm climates this may be exactly what you want. In more temperate zones, the same tiles may create a sense of coldness rather than coolness. And glazed tiles, while attractive in themselves, give the impression of being slippery, which indeed they may be, especially when wet. Remember too that tiles have to be laid on a very smooth and firm foundation; any bumps or aberrations are very obvious in a tiled patio. Embossed tiles or bricks which have been given a slightly roughened appearance in production — often called rustic bricks — help create a warmer and I think more welcoming environment. Bricks are adaptable and look well in any size of garden, although there is a great deal of work involved in laying them.

Concrete slabs are available in all sorts of shapes and sizes, and square, rectangular, octagonal and hexagonal slabs are all popular. And they can be laid quickly and easily. Their bold and individual outlines may, however, come across as too strong and marked in a small garden. Match the size of your paving elements to the size of your garden: the larger your patio, the larger can be the elements. If you have a soil foundation, then spaces can be left in the patio in which to plant shrubs or trees. Where space permits (you do not want to cast too many shadows over the water), four of those marvellously thin, slender and compact scopulorum Junipers could be planted at the four corners of a formal patio pool. They will provide a great depth to the garden by their reflection in the water.

Raised beds offer another, and greatly underrated, possibility. The walls of the beds could be made from a contrasting material; the patio might be made of concrete and the beds of brick, or one might use two different tones of concrete. A different tile, brick or whatever, might be used as a surround to the pond to highlight it as the central feature. Contrasting colours can, of course, be used as ‘veins’ in the pattern of the patio, but without an experienced eye such attempts may turn out woefully fussy and over done. Simplicity is no sin.

Informal ponds

And simplicity is certainly no sin in the design of a formal pond. For it is precisely by its broad sweeps and well defined lines that a formal water scheme makes its appeal. And the same applies to informal ponds. Here one is not aiming at geometric clarity; but a natural water scheme is quite different from a chaotic one, and it is achieved by simple, well-laid out plantings and groupings of plants. The question is when to opt for a formal pond and when an informal one. Personal taste is likely to be the first consideration, but the layout of your garden as it already exists needs to be taken into consideration. By and large, a highly formalized garden with trees, shrubs and hedges laid out with geometric precision, demands a pond of equal precision. As a general rule the lines of the pond should conform with the lines of the adjacent hedges or walls. The overall geometric layouts must be one of harmony. Strong lines that do not run parallel or are not laid out at very definite angles will look awful.

That said, geometric and formal lines are more easily destroyed than created. Should you inherit a formal garden and wish to alter it, nothing could be easier. The severity of a hedge can be softened by the planting of shrubs at various places along its length. A geometric border can be made into an informal one, simply by cutting out curved sections along its edge. An informal pond, if combined with a rockery, is not so likely to clash with an otherwise formal garden. If you create a rockery, make sure the rocks or boulders you use are buried in the soil to at least half their height, preferably more. You might think it a waste of rock and effort to conceal it. But a rock simply stuck on top of the soil looks very unnatural.

Waterfalls

A rockery opens up the possibility of including a waterfall, which can be made in a number of ways. Fibreglass ‘saucers’ are obtainable and these are simply sunk into the rockery, so that water falls from one saucer into the next without any water spattering on to the surrounding soil, otherwise the level of the pond will drop. Simple as fibreglass saucers are to install, they hardly ever look as natural as those made of concrete. If your concrete saucers are light enough to lift, it is an advantage to make them away from the site and put them in place later. Dig out shallow moulds in some spare ground and line with polythene or straw. Prepare the cement as you would for making a pond, using less aggregate if you wish. A stiff mix is essential. Place in the moulds and smooth to the required shape, having thoroughly embedded chicken-wire as reinforcement. Then at one end form a ‘lip’ about 10 cm. Across. This can be made with a long, flat piece of stone if desired; but it is important that the lip is several centimetres below the level of the surrounding wall, or as water builds up in the saucer it will cascade over the sides as well as the lip. The depth of the saucers need not be equal, but to prevent water spilling over, they should not be too shallow. An average waterfall needs 15 to 30 cm. Once the concrete is hard the saucer can be bedded into position in the rockery. The advantage of making the saucers off site lies in being able to angle them later to obtain the best pour. On the other hand, when making large waterfalls the cascades must be constructed in precisely the right position as they cannot easily be adjusted afterwards. But you can combine the saucers or cascades with rocks (they would be too heavy to move into position from a mould). Make absolutely certain, however, that all rocks and stones embedded in the concrete do not reappear. The inevitable creases and overlaps in the liner are hard to conceal and it is by no means easy to prevent the surrounding soil from continually entering the water course.

Waterfalls and courses can be fed by one of two kinds of pumps. What are known as sub-mersible pumps will provide an output of any-thing from 1000 to 4,500 litres of water per hour, with a head of water of about a metre (the vertical height of the highest cascade above the water level of the pond). As the water head is doubled, the output can be expected to be reduced by about one third. The bore, length and any bends in the outlet pipe will also have a bearing on the output. Usually the pump manufacturer will state the output at various heights, indicating the maximum head possible for that particular model. Up to 1000 litres per hour will provide a gentle tinkling waterfall, while 4,500 litres will be closer to a torrent. For most purposes 2 -3000 litres per hour is quite sufficient.

The pump is simply submerged in the pond so that the chamber of the pump (which contains a centrifugal impeller) is automatically filled with water. The outlet pipe is then underneath. If they do, the likelihood is that water will seep out between the concrete and rocks. A waterfall will look more natural if it begins some way up the rockery rather than at the top.

A water course, where the water runs between rocks and boulders, can be constructed in conjunction with, or instead of, a waterfall. The procedure is the same. Dig out a channel in the rockery and line with concrete and rocks or small boulders. The sides of the channel must be of sufficient height to avoid water spilling over, a special danger where curves are encountered.

The pump should be connected to an electrical point installed near the pond by a qualified electrician. (Water and electricity can make a lethal combination, so it is best not to try such an installation oneself.) By using a T-piece in the outlet pipe, a waterfall and fountain can be fed from the one pump; and by inserting stopcocks in the two outlet pipes it will be possible to vary the output between the waterfall and fountain.

Surface pumps, as they are called, are much more trouble to install than submersible ones and are generally more expensive. But they do have an advantage in that their performance is affected less by the length or height of the outlet pipe; and where a huge display of fountains and cascades is required, surface pumps can provide the output — 15,000 litres per hour if necessary. The surface pump has to be housed in a weatherproof and ventilated container adjacent to the pond. A factor known as ‘suction lift’ has to be taken into account; that is to say the pump must not be more than a certain height above the water level of the pond. But this is rarely a problem, as the suction lift factor (provided with each pump) is not likely to be less than 1.3 metres. An intake pipe is fitted with a strainer and foot-valve (to prevent water pouring back out of the pump when it is not in use). The outlet pipe is put into the top cascade and the system is filled with water: the pump is primed. Perhaps the easiest way to prime the system is to first remove the foot-valve, inject water from a hose pipe into the outlet pipe and then start the pump. The pump cannot draw up water when the impeller chamber is empty and to run the pump when dry may lead to overheating and damage. Once the water is circulating, the valve can be replaced. Then the pump can be stopped and started as required.

To protect the pump from weeds and debris, a corner of the pond can be walled off with fine wire mesh, for example, and the intake pipe placed within.

Water in motion raises the oxygen level in a pond, so fish will appreciate a fountain or waterfall. Water-lilies, unfortunately, will not. They like neither being continually dowsed in water — the flowers will tend to close up and sink — nor do they like disturbed water. So far as a fountain is concerned, unless your pond is large enough to accommodate one in one area and the lilies in another, they make poor companions. Besides, fountains are really only appropriate in formal schemes.

The case against waterfalls has, I think, been overstated. Not only will a waterfall raise the oxygen content but by moving the water through oxygenating plants, it will filter from the water the fine particles of mud held in suspension. Large baskets of Elodea will answer this need very effectively. Place them so that they are directly in line with the current of water. To maximize the filtering function of the waterfall in relation to underwater plants, I would place the intake pipe at the opposite end of the pool to the waterfall. I know that many gardeners would frown at such a practice. Place the intake pipe under the waterfall and minimize water disturbance, is the usual advice. But a reasonable compromise between the needs of the lilies and the filtering process is usually possible, since you are hardly likely to want to run the pump continuously, and where there is no perceptible current, the lilies will hardly notice. A more sophisticated but also more troublesome method of filtering water is possible. A box of fine sand, fitted with a retaining gauze exit and entrance is connected up to the outflow pipe (the intake pipe must never be interfered with). The sand will need to be changed at the end of every season. Properly installed, this is a very efficient method of filtering, but it can be a messy business getting it right. And a point to remember is that the output of the pump will be reduced.

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