Hmmm, this is an interesting idea. Homegrown Revolution writes about raising potatoes in tires. The idea is to add another tire to the stack as the plant grows, thereby producing more potatoes. Very interesting, and what a great way to save space. I do worry about chemicals in tires affecting the potatoes. I need to get with my tire guy to see what he thinks about this. And I need to figure out of potatoes grow in zone 7. Time to research.