If there's one thing I've learnt after working in Gloucestershire for many years, it's that clay soil gets an unfair reputation. Mention heavy clay and many gardeners immediately start apologising for it. They tell me nothing grows, that it becomes rock hard during summer, waterlogged through winter and impossible to dig for much of the year. I've heard people describe it as the worst possible soil to garden on. I understand why. Clay certainly has its challenges. But I've al