I usually find my tires along the side of the road; and I have even found 10 tires piled up in the woods! I know several people who have grown potatoes in tires. Carrots and onions do best in raised beds, which may be great for growing in tires. It's possible to grow any annual or biennial plant in a tire. Something like a tree will not be best suited for growing in a tire.
Personally, I would not grow vegetables in tires (especially if they haven't been completely cleaned). I am using 5 tires for growing Ferns and Chrysanthemums. If I obtain more tires I will continue to grow flowers in them. I would like to paint Tires and create a unique Tire wall as you can see from other gardener's tire gardens-- see below:
|No dime design|
|the Tire Garden|