I made a cheap hugelkultur bed with zero cost input for this. I dug the ground out about 6in below my raised bed frame filled it with tree branches, and leaves and grass clippings then put the sod on it grass side down and then put the dirt I dug out back on top. The idea was to make a really cheap raised bed and fill it for no cost. Then I just decided that would be a good spot to try this experiment.
Your right about it being too warm especially the week I planted it, with the cooler temps this week I might have some luck.