Does anyone out there have feelings about the use of old tires to contain the soil in my greenhouse garden beds? I haven't done much research on the pros and cons of old tires. I like the idea of driving around and picking up the trash from the side of the road. Free supplies and helping clean the neighborhood feels doubly good. I like the ease of construction--just lay a few courses of tires and fill with dirt. I like the idea of circular flower beds in my circular greenhouse.
I guess my concerns are poisoning my plants or poisoning myself. Is there any danger to recycling old tires to grow vegetables in?