Dear Farmer Dill,
Thanks for your prompt reply! In fact no, I've been filling the tires with
more soil, dug beside the tire towers. Perhaps this will be too heavy for
potatoes to form(?) It's sandy and well drained, and I've been

keeping it
moist - not overly so, watering perhaps twice a week. Since it's mid June
now, I thought I'd harvest one stack, and harvest the others as you
recommend for mature potatoes.
Dick Lovering

It should work ok with sandy soil that does not compact. The advantage of using
a mulch material is that it is light compared to soil, contains nurients for
the potato and you are less likely to get a hernia taking the tower apart to
get the potatoes.

dill