Boys I won't profess to knowing anymore than the next guy, but I've done a fair bit of reading - by my own standards - into Dr. Albrechts' work and numerous 'graziers' since his time, and where there's a plant of any type, desirable or not, you can diagnose what your soil needs. I don't know if you've ever had that 'clay dirt' tested Rod, but it would be interesting to know what the levels were of Ca, Mg, Na, etc. I just got my soil samples back from Brookside Labs - which Dr. Albrecht helped start I believe...Doc Harris? - and my best patch of property is a 5 acre piece that grows nothng but clovers, DANDELIONS, and an unknown grass that's thick as hair on a dog. The kicker is that none of it was seeded, it just came in on its own after my Dad brushed it out 20 years ago. There was always big timber in there, and when he brushed and burnt it up, he never got around to seeding anything.
My point though, is that things grow for a reason, not b/c they're just there. What's growing is an indicator or symptom of unbalanced soil, which can only be understood with a sample and analysis.
As for your thistle gardens, why not try putting your salt blocks/oilers/mineral tubs in them? We moved our blocks and tubs into the buckbrush and spherge patches, and the cows trample everything 'til it looks like a roto-tiller went through. After you give it time to come back, the grass just takes over.
