Sharing this from Dirty Little Secrets. It’s probably not exactly the same for container gardening, but definitely something I think I’ll look into. For the area along the back fence I’m guerilla gardening (until management finds out) I think I’ll try a cover crop of daikon radishes. Hopefully, some of those roots can break up the clay to make room for a sunflower garden next spring! We’ll see how it goes…

Get spring gardens off the ground with simple autumn soil care. Soil building starts in the fall.

Source: Don’t Fall Down on the Job – Spring Starts with Autumn Soil Care