If you're starting with a small plant, my guess is you'll need at least a 10-15 gal container, even then, it may need water on a daily basis by the end of summer, but you can always move it up to a larger pot as needed.

I am trying one this year as well, I planted it into a 3 gal container with 1 inch holes all along the sides, and I will plunge it into the ground. In the fall, I will pull out the pot, prune back the roots and most of the leaves, and keep it dormant in my cold garage for the winter.

Thanks! I like the idea of plunging the pot in the ground..