Thank you for sharing this challenge! It sounds like many people here are trying to figure out similar situations. I'm also trying a permaculture approach near Santa Clara, which is super dry in the summer. I don't have any advice to offer except to say that I've come to love my clay soil. It retains water really well once you get a thick mulch on top (I used woodchips from Chip Drop), and in the winter during the rainy season you can propagate cuttings by literally sticking them in the clay. All my plants & trees seem to bust through it just fine if it's reasonably moist. The key is never letting it hardpan, so... more mulch! Best of luck in the future!!
