I have the typical dense bay area adobe clay soil, so it is my thinking that cover crops would add OM and break up the soil (without tilling) and partly to add nitrogen (legumes) to ultimately help the trees. Because of the clay soil, I don't want to have to till at all.

Right now, this area around the trees and around my raised beds, is mulched with the red cedar "gorilla hair" to keep weeds at bay and make a nice material to walk around on.

I've seen the basic list of cover crops on the FAQ but not sure which is best for my specific needs. In particular that I only want to break up the clay soil and I don't really want "friable" soil in that area.

Ideally, I'd love to find cover crops that I could plant under/among the gorilla hair that I could easily cut down without disturbing too much of the mulch. Also not something that will become a weedy mess later on. I have this vision of a forest of fava beans in the fall, but don't know what else to plant to complement the beans, and if there's something I can do during the heat of summer as well.

I saw that sunflowers can be a cover crop for loosening soil, but aren't they allelopathic for fruit trees?

Can I also grow bush beans as a cover crop during summer? Is that something that I can actually harvest for eating, or do I need to cut them down before they set bean pods.

Thanks,
KMama

And the thing about legumes is that they fundamentally alter the soil's internal milieu until well after the legume dies, do you agree?

How about a garden of swiss chard, watermelon, and okra? These are easy to get rid of unlike many traditional cover crops and rot quickly, giving nitrogen less of a chance of leaching off.
A sight specific knowledge of various factors should be understood before developing a cover crop plan, do you agree?

So, going the green manure route requires a better understanding of cover crop and soil interactions, over simply laying out finished compost and a mulch.

Kimmsr, the Davis stuff is cool, but are there any other good sources for layperson/homeowners in a densely planted home garden space?

Mackel, I wouldn't have thought to plant other edibles but may try it (especially since it's still raining today in Northern California and will continue all this week. Ugh.) Most of my edibles are in 2' deep raised wooden beds because nothing grows really well in that native soil. Last year I tried pumpkins in the clay (I think they're pretty similar to watermelon) and they were very weak, small plants that complained if they didn't get a steady stream of water.) I might try that. They might do better, also, if I just sowed them directly in to the soil and see what comes up (rather than planting seedlings like I did last year.)

-KM