Hey Jorge Cervantes book "Marijuana Horticulture: The Indoor/Outdoor Medical Grower's Bible", has a section in it about growing in trees. It's a pretty cool book- worth buying for sure.

I wouldn't personally wanna have to climb a tree everytime I wanted to look after my plants though. I doubt my bf would either, he fell out of a tree when he was 10, ruptured his splein (almost died), and broke both of his arms. Not a good experience to say the least. lol.