How to Improve Clay Soil in the Garden

Even if you have the disadvantage of poorly draining, or even heavy clay, soil, don’t despair and don’t think you can’t plant Yew or any other hedging plant from the long list of those that won’t tolerate being waterlogged. You can – but you will have to prepare its new home before it moves in.
The following is based on advice given by the RHS and if it appears daunting, it is worth remembering that few soil types are more fertile than properly improved clay:
GENERAL
• Don’t work or walk on clay soil when its wet as it will become puddled and compacted – having to put this right will add greatly and unnecessarily to the workload
• These preparatory steps can be undertaken at any time except during the worse of a wet and/or freezing winter or during a heat wave when the soil may well be baked solid
• Frost will break down clay soils so, particularly if you garden in a wet region, dig the soil into narrow ridges to allow frost maximum access
IMPROVING THE SOIL
• Dig in as much organic matter as you can. Manure (with straw still visible) or composted bark are ideal; leafmould, leaf litter and garden or mushroom compost will also be beneficial, but not to the same extent
• Digging in coarse grit, gravel or sand is a common solution, but the quantity required to make a difference is such that it’s only really practical on a small scale
• It is also possible to improve a heavy soil by altering its chemical make-up. Some (though not all) clay soils will benefit from adding calcium, normally in the form of gypsum, the active ingredient in many commercially available clay improvers. However, if the soil is acid, then lime is used to achieve the same effect. However, you should test the treatment in a small area first as soils do not respond in a universal manner when either chemical is added
PLANTING IN IMPROVED SOIL
• Creating 25cm mounds (in effect, a raised bed) for planting can help prevent root damage from waterlogging
• When you have dug the hole for planting, thoroughly break up its bottom and sides with a garden fork
• Delay planting until late winter or later so the dormant roots will have to spend less time in cold, wet soil
ONCE THE PLANTS ARE IN
• Add around 7.5 cm of well-rotted garden compost and/or manure at the base of plants after winter, leaving a7cm exclusion zone around the stem to protect it from the danger of rotting
• Repeat regularly throughout the growing season