I wonder if turmeric can be grown in a zone 6 garden. I think @hoodat grows it where he lives. @Nyboy, do you know someone with RA, or just interested in the findings? Several of us on here have it. Lots of people who are smarter than me say food in the nightshade family (tomatoes, peppers and potatoes) can cause a flare. I sure hope that is not the case for me. Haven't tried to go without them long enough for a test.
You may possibly succeed in zone 6 if you can mulch heavily enough to keep the ground from freezing and if it does not get heavily frosted before it goes dormant. Growing it near a South facing wall may help by creating a warmer microclimate.. It grows with no problems here in San Diego but I am in Sunset zone 21. I always found the Sunset zones more accurate than the official zones since they take a lot more than freezing dates into consideration.