Ask TennZen: Is it safe to grow veggies in tires?

It's time for another edition of "Ask TennZen," in which I do my best to answer your questions. As always, any advice offered here is taken at your own risk. Your mileage may vary.

I've been asked a question regarding our tater tires:

"I've heard a lot about potato tires not being healthy; that the tires can leach into the soil/food. Have you heard anything about this?"

Thank you for your question. I'm glad you asked.

Before deciding to plant vegetables in tires, I did quite a lot of research because I, too, had heard rumors about tires leaching harmful chemicals into the soil.

My research didn't turn up any evidence of this.

The U.S. Environmental Protection Agency provides a wealth of information about scrap tires, their potential harm, and how to properly recycle and reuse them.

It lists two major concerns about harmful chemicals from tires, but only as a result of either burning them or shredding them into mulch. It shows no potential harm resulting from planting in tires. In fact, they even have a picture of some veggies growing in tires!

Ash from burned tires is a toxic material and barren soils have resulted where huge piles of tires burned. In other words, nothing will grow where tires have been burned.

As far as unburned tires, the only potentially toxic metal in tires is zinc. Studies which show soil toxicity resulting from exposure to tires are based on using rubber mulch (i.e. shredded tires) - which radically exposes the zinc to leaching.

As far as planting in whole tires, or in tires with the sidewalls cut out, there is no evidence I can find that indicates zinc leaching from whole, unshredded tires into soil.

I have seen some websites that cited concerns about polycyclic aromatic hydrocarbons (PAHs). According to the Department of Health and Human Services Agency for Toxic Substances & Disease Registry (ATSDR), “Some people who have breathed or touched mixtures of PAHs and other chemicals for long periods of time have developed cancer.”

PAHs are created during the partial burning of, among other things, oil, gas, and tires. PAHs are created during the heating process of turning tires into pelletized synthetic turf like FieldTurf (NOT tire mulch). Studies have shown that the levels of 6 PAHs found in the rubber pellets were above concentrations allowed by the New York State Department of Environmental Conservation. But in ALL cases, the PAHs were not leached from whole tires. Only from partially burned tires or pelletized tires.

To summarize: Yes, tires contain potentially harmful chemicals. But studies show that the chemicals are released only when tires are burned, melted, pelletized or shredded. There is no scientific evidence that shows any harmful chemical release from whole, unshredded tires.

I also talked to several farmers/growers who planted in tires for 12 years or more. No one stated any problem with plant growth or produce quality.

It turns out that any problems people experience with planting in tires are the exact same problems gardeners run into using any containers - mainly watering and nutrient leaching (fertilizing) issues.

But people who understand container gardening and know about the added demands of vegetables grown in containers usually have no problems. About the only real problem I've seen is where the plants get too hot in southern climates. In those instances, painting the tires white usually cleared it up.

I hope this helps!