I've enjoyed everything I've read by Johnson. I used to have a link to a poem called, I think, "The Green Man", which was wonderful. I've read exerpts of the work mentioned in the OP. I think Johnson is one of our neglected geniuses, definitely belongs in the Pound-Zukofsky-Olson-Duncan strata.
Found it. It's called "The Book of the Green Man"
http://www.thing.net/~grist/ld/rjohnson/rj-gm-1.htm