Gardening: How to improve wet clay soil | Brian Kidd

Last week’s article inspired two allotment holders at Fareham to write to me about improving wet clay soil.Have no doubt about it, if worked well, clay soil is very fertile. The secret of success however is to work with the clay when conditions are right.

Saturday, 7th December 2019, 6:00 am
Digging clay soil to make it friendlier. Picture: Shutterstock

Clay is difficult to deal with because of it's structure. It consists of uncountable millions of particles which are plate-shaped and they all stick together.

The only way to resolve this is to increase the air in the clay and to add as much in the way of organic material as possible.

Because this task is daunting, it's wise to start to improve one area at a time and if done well the result will be a permanent solution to the problem.

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If an area is to be dug, it is best tackled in early winter, so, right now because we have had some rain. If clay is dry it is difficult to dig.

Instead of using a spade to do this digging, it's easier to penetrate it with a stainless steel digging fork.

A trench should be taken out of of one end of the area to be improved and in the bottom a generous amount of straw should be laid. Stable manure with lots of straw is ideal but straw on its own is just as effective.

As digging proceeds, a little at a time if it is really difficult, so great clods are thrown forward. Leave them in lumps as large or even larger than house bricks. Never try to break them down at this stage.

Once a line of digging is completed, place another thick layer of straw in the bottom of the trench and if some of it is still visible after the clods have been thrown forward, it means you are using enough which is all for the good.

You can lime the ground immediately after digging. Eight ounces of garden lime on each square yard, but lime must not be used where acid-loving plants will be grown.

Lime flocculates (breaks into small lumps) the soil with each frost. The water in the clay freezes and swells so when the soil thaws water penetrates even deeper into the clay. In turn it swells and fissures are created. These are fine lines within the clay which attract even more water.

After further rain the clay can absorb even more water which will freeze during frosts and so on. This process continues all winter. Wind also plays its part in drying the surface of the sods which all helps to break down the clay.

My final recommendation is to apply a thick layer of sharp sand or fine grit all over the surface, about two inches deep is ideal but this is best left until about the middle of February.

The spring rains will help the grit particles to fall into the crevices and fissures and this dressing often disappears quickly but remember to keep working with the weather not against it so that by April you should be able to walk over the surface to lightly cultivate it.

If the surface is dry enough it should be fluffy. A good test is to kick it. If it's OK, the particles will be fluffy and move easily, but if the surface is wet, keep off.


Did you plant hyacinths in pots in October? They should have been kept cold and in a dark place. But now is the time to bring them indoors provided the shoots are four to five inches tall.

If you forgot to plant them, pop along to your garden centre where you will find pots of hyacinths with strong buds just showing colour. These will be in full bloom for Christmas. Remember, they have a lovely perfume.