Your question brought back a long ago memory. Walking through the extensive vineyard of a master New York State vinter he told me that established grape vines send roots 100' downward into the soil. Cannot say that this is true or not. I just always remembered his claim. Two thoughts as I read your question: 1. The new concrete will leach lime for many years raising the soil pH beyond the comfort level of growing any plant, including grapes. This means working with and amending the soil for about the first ten years with acidic compost or commercial products for this purpose. 2. Your plan of a seating area works. Check with some local growers of trees to see if you can find a very large, heavy duty plastic pot, remove the bottom, sink it in the hole and plant. This would be the ideal solution, forcing the root system down. Second choice would be lining the planting hole with 5 mil plastic sheeting. And, grapes grow quickly. It would be an easy job to kill off one that has grown out-of-bounds and replant with a new one.

European varieties are usually grafted for phyloxera resistance since they don't have any natural resistance. If you have American varieties they usually aren't grafted.

Thank you! In that case, I will care for it as long as possible inside and then offer it to a friend. To be honest, I was hoping it would be possible to have a sort of "living wall" using the grapevine. My room faces the sunrise, so the plant would receive light in the morning, and artificial light once the morning light becomes weak. Any specific reasons why you don't think it would survive indoors?

I got Reliance from Stark Bros last year. Parts of CA are OK, for example my zip is 95032 and they will ship there. Perhaps you can find someone to take delivery for you...