I now garden on heavy clay, topped with 18" -24"of topsoil. The clay is acid - everyone else around grows beautiful Camellias and rhododendrons - but the topsoil is quite different, the Camellias I have here are usually on the yellow side. I've tried Sequestrene, which doesn't help much. What would happen if I used almost-2-year old conifer chippings around the Camellias and Rhododendrons to attempt to acidify the soil? They seem quite well established. We've been here for 18 months and they have been here much longer than that.