Water Garden Islands

An island is rarely suitable for a small pool. Not only will it look out of keeping, but also, given the diminutive scale on which it will need constructing, it will not be of any significant use. With a small body of water, the only justification for constructing an island is to provide a predator-free haven in a wildlife pool. Even then, if the pool less than about 4.5m (15ft) square, it will not serve much useful purpose.

 

CREATING AN ISLAND

How you create a water garden island will depend upon the type of pond you intend constructing. The scale of the excavation will help you decide whether to dig out the pond entirely, seal it, then build a water garden island, or dig out the pool to leave an island. In the latter case, unless you intend sealing the pool with a bentonite blanket, or lining it with concrete, making the pool watertight may be quite difficult. A liner can be used, but its shape is likely to be rather awkward, unless you choose a rubber example and have it cut and welded to suit. The major benefit of creating an island in this way, however, is that it can be formed around an existing large shrub or tree to give an instant sense of maturity.

If an island is to be created after the pond has been excavated and lined, or sealed, there are several methods of construction to choose from. The simplest and most natural-looking is to build the island while the pool is empty, using hessian sacks filled with soil. These can be arranged to form a hollow square, or similar shape, which can be filled with soil. To ensure that the pool does not receive excessive quantities of nutrients, all but the top 30cm (12in) of soil, in which plants will be grown, should be of poor quality, preferably subsoil. As an alternative, a substantial amount of the space in the centre of the island can be filled with hardcore, provided it does not include any limey material, which may pollute the water. Once the pool has been filled with water and the soil is well soaked, you can begin to plant up the island.

In a concrete pool, an excellent stable island can be constructed from blockwork, which should be built to within 10cm (4in) of the normal water level. Marine plywood boards should be fastened around the top of the blockwork, with brass screws and wall plugs, so that they just break the surface of the water and act as a timber edging. Then the centre of the island should be filled with soil, or with a combination of hardcore and soil, to create the island above the water level.

A water garden island does not have to be covered completely with vegetation; it can be a rocky outcrop with pockets of soil, in which small plants can grow. The rocks should be concreted to the floor of the pool and gradually built up to form the island shape, the centre being filled with more concrete to ensure stability. If you use rocks in this way, make sure that you use Only good-quality material, and that the strata all lie in the same direction once they have emerged from the water. Sandstone and limestone rocks should be avoided, as they will crumble and flake during freezing winter conditions.

 

METHODS FOR CREATING AN ISLAND IN A POOL

It is possible to create an island by contouring the excavation when the water garden is constructed.

This demands a high degree of accuracy with levelling from the outset.

A simple island can be constructed with bricks or blockwork and finished naturally with wood at water level. This edging disguises the structure beneath and appears more natural.

A soil or sand bag construction gives greater flexibility with the shape and size of the island. It soon mellows into its surroundings and plants and algae also establish on it freely.

A wooden pallet secured to the pool floor is an economical form of construction for a floating island. The discreetly hidden plastic bottles provide added buoyancy.

Apart from the simple water garden islands described here, if you become really enthusiastic about wildlife, you can create duck huts and similar island accommodation for breeding and sheltering wildfowl. However, these are very specialized, and advice on their construction is best sought from a local nature conservation group or similar organization.

 

THE FLOATING ISLAND

Creating the elaborate structure needed for a permanent island will not suit everyone. However, an inexpensive alternative is to make a floating island (see 3 above). The basis for this can be an old wooden pallet or a construction similar to a section of decking. This should float quite successfully, but depending upon the timber used, and the scale of the island, you may need to add some extra buoyancy. Old plastic soft-drink bottles and similar containers are ideal for this and can often be concealed within the island raft. The island should be secured by a nylon cord to a suitable anchor, such as a piece of concrete with a large metal staple embedded in the top. The length of the cord will determine the amount by which the island is allowed to move around on the surface of, the water; if the cord’s length is equal to the depth of the pool, the island will remain in a fixed position.

With a little care, it should be possible to accommodate some plant life on the floating island. This can be planted in small growing bags made from old tights. Fill the tights with good garden soil, soak them thoroughly until the soil is sloppy and malleable, then plant small rooted cuttings of water mint or brooklime through slits cut in the tights. You could also add a small rush or water forget-me-not. Push the growing bags into the gaps between the wooden boards of the island. The plants will establish quickly and, provided that you add only a few, the weight will not be excessive.

When the use of soil is impractical and may cause the island to sink, jam cut willow stems into the gaps between the boards. They will root into the water and produce a seasonal small bush, which will have to be discarded at the approach of winter.