Provided you have enough room and some spare cash (pools start at about £15,000), our increasingly frequent hot summers justify installing one. But I’ve always had a problem with traditional swimming pools in Britain. These chemically maintained, turquoise rectangles are a bit “footballers’ wives”. Better suited to countries where the sky is blue from May to September, they look glossy and glamorous on holiday but out of place back in Blighty.
A stone-lined pool is an alternative — the water is a less garish pale greenish-blue — but, for both aesthetic and ecological reasons, my first choice, given a suitable location, would be a swimming pond. The muted colours of a limpid lake are more in keeping with our soft light, and a lush edging of grass and foliage is also more appropriate in Britain than the harshness of tiles and stone.
Inspired by alpine lakes, swimming ponds were developed in Austria and Germany, where they have been in use for the past 25 years. They are now the height of fashion over here. Having featured at both the RHS Chelsea and RHS Hampton Court flower shows since the beginning of this century, they are an alternative to a conventional pool for those in the know. They retain the cachet of exclusivity for good reason — starting at about £35,000 to install, you can see why — but a swimming pond also shows an aspirational awareness of environmental issues.
The idea is simple. Rather than using chemicals such as chlorine to keep the water clean, plants with cleansing properties are grown in one section of the pool, the regeneration zone. The gravel substratum in which the plants are grown acts as a natural filter as water passes through it. Rooted into this the plants, such as reeds, water lilies, flowering rushes, Cyperus longus and yellow flag irises, do their job of taking nitrates out of the water and reducing phosphates. It’s a physical and chemical double act, gravel and plants working together to create a well-balanced natural filtration and cleaning system.
According to Steve Day of Anglo Swimming Ponds, it’s not hugely difficult to get right. “As long as you give the pond everything it needs, nature will find the correct balance.”
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The planted section of the pond is generally kept separate from the deeper swimming zone by a physical barrier. This underwater vertical wall stops short of the surface of the pond so that water can flow freely between the two areas, creating an unbroken visual line. In this way, the plants can do their job but not impede recreational use.
Unlike our Teutonic cousins, however, we often put aesthetics above efficiency. “We tend to put in a wider variety of plants because the English gardener wants to see something that looks pretty, as well as being able to deal with the mechanics of cleaning the water,” says Day. “For example, water lilies don’t do that much in terms of water cleaning, but they look nice.”
Choosing a good site is important. First and foremost, you need enough space. “The smallest we would recommend is 120sq m, to give you enough room to swim,” says Day. This includes the planted section, which accounts for about half of the total area. However, the larger the pond, the greater the swimming zone can be in relation to the regeneration zone, as there will be enough plants to keep the pond clean.
Although the plants can cope with some shade and could be introduced at one end of a partially shaded location, an open site is best and most pleasant to swim in. Under large trees is really a no-no because the debris is likely to fall into the water in autumn. Anything that falls in will rot and the pond will have to deal with it.
The practicalities of positioning aside, where you put your pond will depend on the atmosphere you wish to create. The classic approach is to integrate a naturalistic pond into the landscape. Copying nature looks great in the right setting — probably one with lots of space and a rural backdrop — but is not the only option. Swimming ponds can also be sleek and sophisticated, fitting into a modern or urban environment.
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The Moat and Castle Eco-Garden included just such a pond at Chelsea last year. Elma Fenton and Neil Malachy Black designed a sophisticated rectangular pool with a regeneration zone at one end, and a narrow bed of marginal plants, including water irises, running the length of the pond.
This all sounds wonderful, but is there a downside? Are the ponds really clean enough for my children to swim in, and what about undesirables — namely rats — sharing the pool?
“Well, I wouldn’t recommend putting the pond next to an orchard, for instance, with rotting apples rolling into the water,” says Day. “Other than that, it doesn’t seem to be a problem because the water is very clean, so rats aren’t interested.”
Day does admit that blanket weed can be a nuisance with newly installed ponds, particularly towards the end of a hot summer. This improves as the pond matures, a process that can take up to two years. “It depends how you want it to look; often, the actual swimming area is still as clean as clean can be, even if there is quite a significant amount of blanket weed in the planted section.”
However, the general upkeep is low, consisting mostly of good gardening practice, including cutting down the reeds on an annual basis.
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Deadheading is also important for the look of the pond; and, if you want it absolutely spotless, you can get a vacuum that removes bits and bobs from the water. But many owners have a maintenance contract for a one-off autumnal clean-up.
When it comes to attracting wildlife, rats aside, most visitors to the pond are more than welcome. “Frogs and newts are actually quite beneficial because they do a good job of clearing up the edges of the pond,” says Day — and damselflies and dragonflies look lovely darting over the water. However, fish are not encouraged because they would strain the pond’s carefully balanced ecosystem. So you may never know what it feels like to swim with koi carp.