Hi, I'm new here. Been gardening since forever really. I live in the urban thralls of London and after three years of hit or miss with planting I want to take matters in my own hand and repair my depleted soil. It's pretty poor and I regulary find all sorts of debris in it (rocks, bricks chips, bits of tile and glass) which I shift out, but what would be good to add to it in order to save it from state that it's in now. I mainly grow flowers and veg, if that matters to the type of nutrients I'll need. Any advice would be helpful. Thanks.