OK this may seem dumb, but I wanted to make sure I wasn't assuming something that I thought was obvious..
Are turnip /mustard/beet/collard greens (What is collard?) simpley the leaves of the afore mentioned plants?
The reason I ask is that there is a ratty old greenhouse in my backyard, Originally I was toying with screwing it in to the side of my house around the window for a basking area next summer, but I was thinking as I looked at this months food bill ($200+ just for the various animals in this house) that I could grow my own, and even if I couldn't grow lots, Spike would most likley enjoy ripping up some still growing plant... and most likely be healthier for him as well. Also what other things might I grow for him in there living in NW Washington state
You have an excellent opportunity to grow your own foods!! For advice on how to go about doing this there is a group dedicated specifically to the growing of foods for exotic animals: groups.yahoo.com/group/ExoticPetsGardening