Friday, 23 March 2007


If you think it’s too cold for light garden duties, get your spade ready for some serious digging of drainage channels. (Better still; get someone else to dig them!)

Most trees, bushes and plants don’t grow in waterlogged soil. The most likely cause of this, especially in the garden of a new house is that the garden is made from a layer of subsoil dumped during excavations or building work and then covered with a thin layer of topsoil to finish off. The subsoil quickly becomes a solid layer that prevents drainage. In these cases breaking up this layer means the water can drain away. Start by digging a hole about 3 feet (1m) wide and deep to see how far down the topsoil goes and how quickly the water drains away after rain. If it doesn’t drain away then artificial drainage is needed. If your site does need draining you will have to install an underground system with pipes of either clay or flexible plastic. These are laid to a pattern (usually herringbone) with feeder runs to the main outlet pipe running to a neighbouring ditch or a soak-away. The depth of the drain depends on when you reach the layer of subsoil usually between 2 and 3 feet. The trench is most commonly dug in a V shape, which holds the pipe in place.

The problem in many gardens is where to take the water when it runs down the drainage pipes. If you don’t have a ditch or a surface water drainage system for the water to drain away then it may be necessary to dig a soakaway. A hole 3ft(1m) wide and 3 ft (1m) deep (if you can dig down that far!) can be prepared in an area of the garden where the pipes lead. This hole is then filled with rubble or stone and the topsoil is then put back in place. You can now plant on this soil. It is best to site your soak-away a good distance from the house.

Types of drainage material.
Concrete or clay pipe-These can be bought in short lengths and put in place leaving small gaps to allow the water through. These could move out of place and cause them to block up. I have heard of these lasting a few lifetimes without any problems though.Plastic pipe. - This is bought in continuous strips and cut to length. They have small holes all the way around them to let the water soak through.


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