I stuck a Viking potato in a 5 gallon bucket and kept adding potting soil to it. The soil is about 5" below the top of the bucket and the potato plant is at least a foot above the top of the bucket.The plastic tubs work well. I'm using 1/2 plastic drums and 45 gallon tree planters. The chickens love them to dust bath in.Had to ring them with wire. Just keep adding compost on top and plant away.