Aside from just letting "nature" grow up, we've thrown mustard and alfalfa seed in there just to grow something that has lots of biomass relative to the effort level. This is the year we are cleaning it up and putting in 16" deep raised beds, putting a charcoal and weed-block paper barrier at the bottom and filling with new topsail from a local organic farm. It's a LOT of work, but we feel it's worth it.