Mulch mulch and more mulch is a must for getting humus into clay soil.

Does your soil sticks to your shoes and garden tools like glue? Is your soil slow to warm up in the spring and hard to manage? If your soil is slow draining, forms big clods, crusts over and cracks in dry weather then you have clay or even heavy clay soil.
Clay soil is made up from very fine particles that make pure clay good for potters but not plant roots. One redeeming feature is that clay soil is generally rich in nutrients.

Improving Clay Soil

• If gritty sandy soil is the opposite of clay soil it follows that mixing the two may get the best of both worlds. Add copious quantities of grit or gritty sand to your clay soil to open it up. Do not use builders sand as it is very alkaline or fine sand that will set like concrete.

• Add even more copious quantities, 6 ” plus, of organic matter such as compost. I have tried wood chippings, spent mushroom compost, old feathers, composted bark and various other items to open up the texture. Dig it well in to the top 10″ as you not only incorporate the organic matter but you add air to the soil and help drainage.

• Mulch with compost as often as possible and let worms drag it down into the soil.

• Earthworms thrive on humus and breed rapidly if the conditions are right. You only need a handful or two to get things going so put a few on the soil when incorporating the compost.

• Improving your clay soil will take time and patience.

Plants for Clay Soil.

• Special seed mixes of wild flowers are available from Amazon

• Roses have strong roots that get through clay soils and thrive on the fertility.

• Phormiums seem to do quite well.

• For shrubs choose from Berberis , Chaenomeles (Ornamental or Japanese quince) Choisya ternata, (Mexican orange blossom) or Dogwoods.

• For root vegetables you could try using a raised bed but green vegetables will be successful as long as they are watered as needed.

• RHS recommends the following trees Abies koreana,  Chamaecyparis lawsoniana, Ginkgo biloba AGM,  Juniperus chinensis, Picea omorika AGM, Picea orientalis AGM

• Herbaceous plants include Hostas, Asters,  Knipholia and Hellebores