Holy cow. Mine are at the most 12" or even less in the pots. I grew I grew the Yukon Gold and Kennebec. I am thinking of Yukon Gold, German Butterball and the Kennebec again. I am fighting potato scab though and not sure what to do about that. Doesn't hurt the potatoes but makes boiling them in their skins or baking pretty impossible. The pots sit in a cold shed all winter but I guess that doesn't kill the virus. I used new dirt in most of the pots last year and some came through clean, some not. Not sure how you would sterilize felt pots. The picture of stuffing them in my microwave is not pretty; same with the oven. Guess they could be put in a 33 gallon barrel with some sort of fungicide and water. I will go to the cooperative extension and ask.