I have been using 55 and 30 gallon plastic drums cut in half both ways with good results using soil I make, the center ring when cutting them in thirds, vertically, makes an excellent ring for cabbage, tomatoes etc. Actually I make a 2 foot high bench using 8 to 10 foot long 2x6s and 2 foot 4x4s for the legs to put the half barrels on, gives me a no weed and no bend garden for lettuce, radishes, onions, kale etc. and it is easy to cover with shade cloth from april on using pvc as a frame. The potatoes, corn , squash is grown in the ground although squash and cukes do good in the barrels.