Posted: 17/06/2017 at 17:13
Graham, it's good news that you have soil under your planters. Make raised beds with no bottom and, this autumn, put a 4-6 inch layer of well-rotted manure on top and leave them like that over the winter. The worms will come up from the soil below and pull the manure down into the soil, so all you'll need to do in the spring is some light cultivation. If you put a 2 inch layer down each following autumn, you will keep the soil productive and will never have to dig again. As time goes by the clay beneath will turn into great soil and your beds will effectively get deeper, all by themselves.