This year I am going to try to grow potatoes in 4 x 4 wooden bins that dh built. For soil we are using aged composted horse manure. My question is, how closely can potatoes be spaced? Right now I think I have more seed potatoes than I have space for in the bins; I am thinking with 6 to 8 inch spacing I can plant sixteen tubers in each bin. And no, where I am (Minnesota, zone 3) it's definitely not too late to plant potatoes!