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Urban gardening is everywhere nowadays. People are growing lettuce in their windowsills, keeping chickens in their tiny modular kitchens and using every and any patch of arable land to plant fresh herbs and vegetables. It all sounds so wholesome, doesn’t it? But if you live in a city, chances are the soil in your yard has seen its share of shit over the years. And eating foods grown in it might not be as healthy as it sounds.

In New York, for example, which just happens to be a city where urban gardening has blown up, various soil testing labs are finding levels of lead that are 20-25 times higher than what the Environmental Protection Agency deems safe. So what should you do if you’re concerned about the produce in your urban garden? For starters, get it tested.

A number of universities around the country have soil testing labs that provide free or affordable basic soil quality tests for urban gardeners. At Brooklyn College, you can mail in a sample for a basic evaluation ($45) to find out your soil’s pH, salt content, important nutrients and heavy metal content (including lead). Results are available within a week.

Zhongqi Cheng, Director of Brooklyn College’s Environmental Sciences Analytical Center, which includes the soil testing lab, highly recommends having your soil tested – especially if there are young children or pregnant women in your home. He has received samples from as far away as Texas and California. In New York, he says, North Brooklyn and Lower Manhattan are the most lead-contaminated areas.

“These regions are the old industrial areas, the old centers of town,” he explains, “and it’s the same story in New Orleans, Boston, Philly… It’s amazing.”

So what should you do if your soil is found to be contaminated? Burn your crops and never set foot in the backyard again? Not exactly. If contamination levels are very high, you should contact the E.P.A.‘s Technical Assistance to Brownfields (TAB) program. If levels are only somewhat elevated, Cheng says there are several steps a home gardener can take.

“Add a new layer of soil, say, six to eight inches,” he suggests. “Place a landscape fabric over the ground soil before laying down the new topsoil. You can also do a thick layer of mulch. You want to create a barrier between the topsoil and the ground soil… And if you compost it always helps.”

Landscaping projects can get expensive. If you have to put off adding soil or replacing it completely, you’ll want to be careful around your contaminated soil in the meantime. Cheng recommends wearing gloves while gardening and washing your hands afterwards. Plant-wise, avoid leafy greens: they absorb heavy metals, like lead, from the soil. Be careful with root vegetables, too, as dirt tends to stick to them. Wash all your vegetables well, and peel anything that grows in direct contact with ground soil.

It’s not all bad news: crops like tomatoes and summer squash don’t really absorb lead, so most people can grow these without much worry. You can also use certain plants for phytoremediation therapy. Growing greens like spinach and kale for a few seasons has been show to help reduce lead levels in soil. Planters are another great way to go because you can avoid the ground soil issue altogether.

Whatever you do, don’t give up on gardening. Like so many things in cities – having a dog, raising a kid – it may be harder to do than out in the country, but the rewards can be all the greater.

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