I always order from Steele Plant Company.
http://www.sweetpotatoplant.co...
I always have great results with Beauregard (red) and O'Henry (a white one.) I usually call them on the phone because their website is a little confusing and I never want to make a mistake. There's a big price break the more you buy. If you had others in your area that you could split an order with, that'd be perfect.
