Norteno, I've been wintering my nana's in my crawl space for several years with good success here in Z6. My dad uses his garage and my buddy uses his basement. All work well. What you want is an area with little or no light, not too warm(dry out) and not too wet(rot). One advantage that a crawlspace lacks is you can't see them should something occur. For example we got a lot of water under our house from a wet winter that I was unaware of and I lost several nana's do to rot. It's partly my fault for not putting them up high enough were they would stay dry. Also for you might wanna check there moisture level periodically since you have a fairly warm winter. My buddy uses his basement and keeps his in pots. He lets them stay VERY dry and has the room lit w/small fluorescents. My pops puts his in a closet in his unheated garage, bare root and never touches them. I really think all your nana's would survive in your area w/a lil protection but that's my take on the matter. Why do people try to winter them in the ground you ask. Mainly because it's a pain in the butt to dig em up every year and haul them in, especially when they get big and you get a lot of them. Also they do it just for the thrill of saying they did it. Hope this helps. -Nate
PS.-you might run this by Bigdog. He's had a lot of experience in wintering.