I have heavy clay soil that turns to concrete by summer's end. My dahlias grow in a knot and do not extend their toes down or even out very far. My husband is going to make a subsoiler tooth to attach to the sway bar of our tractor that will go down about 16-24 inches to loosen up the hard pan. I have a couple of yards of finished compost and hope to have a couple more by spring. Plus I have been getting sand down near the Cowlitz River. It's sand/volcanic ash from when Mount. St. Helen's blew and the core of engineers had to dredge the river because it clogged up. I also have a couple of piles of used potting soil. I plan to put all that onto the bed and til it in after using the subsoiler. Anyone have any ideas?