The most durable finish for outdoors (IMO) is marine-grade spar varnish. You can add an oil-based tint or dye to it to color it, for a one-step application. Lots of fussing around to find the right tint but it works. Except pine, which seems to come out blotchy no matter what stain you used. CB.
Clark - does the spar varnish harden into a barrier finish? I've always been leery of barrier finishes on green wood. I've had some bad luck with poly and varnish - hazing, cracking, etc.
Have you a secret? Or does it work?
-Mike