I would imagine that tires are not a good idea to use as a pot all that oil leeching 

Found this picture on the internet 

 

Great idea for those growing in wet areas. It looks like something I would do.

and what would you fertilize with? LOL

You don't want to know!

Those tires look like they still have tread on them... what a waste.  Lol.

Very creative.

What would you use for uppotting? Truck tires?

Hi,
What if the upper or middle tire slips ? Someone pushing, or with the wind ?
The idea is not bad, but simply using an 80 Liters trashcan is in my opinion safer and prettier.

Igor, I love your thought!

I have some painted ones with flowers on top of my rockery... I like it... here is another example.... all recycling is good and yes, the black rubber makes it hot. may not be good if you are already in a very hot area... hopefully, each tire holds a bit of water for the plant.
https://www.google.com/images?q=flowers+on+tires&rls=com.microsoft:en-us:IE-SearchBox&oe=&gws_rd=ssl&hl=en&sa=X&oi=image_result_group&ei=cwJVVKgOqduJAsbfgdgB&ved=0CB0QsAQ

greenfig you can use this tire 

 

I dont know if i would be eating figs grown in that pot

When it's time for the fig shuffle you can just roll it into the garage......Brilliant!!! (now for some reason I want a Guinness)