Not sure about the chemicals. They may have some impact but it's probably negligable. I went wood bins as a similar alternative for the astetics factor. Either way works.

Here is a link that might be useful: Sinfonian's garden adventure!

I've got the same concerns with tires as you!
I've heard of people doing potatoes in tires so they can add tires to add height to the tater planter.
I'll be going to an organic nursery some time this week and will ask their opinion of using the tires.
Nancy

gardenwheels, I grow potatoes in used tires for the heat factor. I have done this for a lot of years due to the fact it could freeze any night of the year here in zone 3. You are in zone 5 and it may cook your Vegetables. Make sure you plant something that will love the extra heat. They are easy to move around but, I built a raised bed at my GF place and it is secured in the ground by the 4 corner stakes only. I drove a couple more down the outside of each side for support. I will be able to move it easily if her landlord ever says anything about it.
I hope this helps,
James

I too live in zone 5 is SE Michigan. This is the first garden in 7 years so this experience is old...

I tried tires years ago and found they were great at warming the soil in the spring and keeping it hot in the fall. I was very successful with greens, lettuce, spinach etc. The tomatoes liked it very well until the extreme temps of summer hit. It seemed like I watered constantly but everything fried in temps above 80 in full sun.

I am not sure about the chemicals but now that I am trying to grow as organic as possible, I would skip them unless I have good evidence that nothing bad leeches from them.

This year I have a 4'x24'x12" "Square Foot" bed and have had an abundance of bush beans (just now pulled some and replanted since they are noticeably slowing down production), just composted the end of the peas, the tomatoes are just starting to come in daily, picked a few nice peppers the past couple days and the corn is starting to set ears.

In this small space I have...10 tomato plants (spaced indeterminate then determinate), 16 sweet corn, a ground cherry, 10 peppers, 2 zucchini, 2 bush cucumbers, 45 bush beans, and a sugar baby melon weaved in and out of the plants.

Here is a picture I took around the 4th of July.
{{gwi:30814}}

Hop on over to the Square Foot Gardening forum for more information if you are interested. The originator of this method uses 4'x4' beds but I know many who use 2'x? size beds successfully. The best things for me so far using this method (besides the great yield) are 1) I control the soil, 2) I placed 1 50' soaker hose 1' inside both edges of the bed and get excellent water coverage and 3) for me the best thing, it is easy to weed! (the few I get).

HTH, Kim

I am employing just one used racing car tire (nice and fat) in my garden at this time, and it has a bodacious Italian Marrow squash plant spilling out of it. I spray-painted it a nice earthy green color. To me, it's just another free raised bed. You may as well try one to see if you dig it.

I have used tires along a fence behind my garage and back fence for the last two years and plan a couple more for next year. The cucumbers I plant in them love it. I plant usually 3-4 cucumbers plants per tire and then produce great. Mine only get 3 hours of direct sun a day, so I only need to water once every other day, but with more sun you may need to water daily.

Dean

Thank you all for the advice and ideas. GW