Whether it's unattainable fresh produce, frugality, or global warming that motivated the creation of your edible garden, the risk of toxic soil in urban and even suburban agriculture is a relevant concern. Typically found heavy metals such as lead and mercury or arsenic and petroleum can be found in soil where old homes, buildings, landfills or heavily trafficked highways once stood or still stand.
Truthfully, most of us living in cities will at least find some small trace of lead due to the once sizable use of lead-based paint, lead gasoline and industrial emissions in our areas. Even though lead materials are now banned and highly regulated, their remnants still exist in our soil and are loosely monitored.
Samantha Langley-Turnbaugh, University of South Maine Assistant Professor reports, the USEPA Final Rule on lead established a soil lead hazard at 400 mg/kg for bare soil in play areas and an average of 1200 mg/kg for bare soil in the remainder of the yard. Yet European and Canadian standard are much more stringent, both requiring less than 150mg/kg.
Anyone planting edible plants in soil around their home should first test it for chemical levels deemed hazardous by the EPA. Thankfully, it's easy and relatively inexpensive or free to test soil, just check in with your state or local university.
And yet even with toxic soil, you have several remedies to choose from so you can continue growing fresh edible produce.
So You Have Toxic Soil, Now What?
I spoke to New York City Urban Landscape Designer Jonathan Yevin from M.U.D. Landscaping about some of the best options.
1. Use Compost and Mulch Yevin suggests, "The most effective way to reduce the level of lead is to add compost and mulch as much as possible every year and continue to test. Adding organic matter to the soil prevents plants from picking up the lead as it attaches to the organic matter instead."
This sustainable solution simply put means using plants to remedy the soil for future plants. Yevin confirmed there are specific types of crops like leafy greens or ferns, that you can plant, and then carefully discard of, which do a great job of naturally absorbing large quantities of harmful chemicals, more so than other crops. Therefore you can use these plants to soak up toxins, but he warns, you cannot eat these plants—you must dispose of them as toxic waste. That means do not throw these toxin-soaked greens in the compost heap or the garbage can either. Looking for a quick fix? 3. Build Raised Beds A little more cost involved since you will need to purchase clean soil and materials, but a raised garden bed can withstand long periods of time, and really add texture and height to your space, not to mention a toxin-free breeding ground for your edibles. "Lead only leaches downwards, so as long as your raised bed is 6-8 inches deep—deep enough for most leafy greens, radishes and onions—they should be safe," Yevin explains. 4. Grow Food in Pot Containers An easier and tiny alternative to raised garden beds are pot gardens. These small containers are great for herbs, tomatoes, eggplant, lettuce, and even strawberries. And another bonus, if you live in a cold climate, you can bring your edible pots in doors and continue growing small batches of food all year. 5. # Stick to Above-Ground Fruit and Vegetables "The scientific consensus suggests that lead cannot be absorbed into vegetables in any significant amount. So [lead] does not need to change all of your plans for vegetable gardening as the it is only absorbed by the leaves of plants, not by fruit and seeds," Yevin reassures. He suggests above the ground edibles such as tomatoes, beans, cucumbers, berries, and peppers, are all okay as long as you don't eat the leaves. Any root vegetable should not be consumed, however, since it spends its life submerged in the toxic-soil. And Make sure to wash all above-ground fruits and vegetables well using a solution of vinegar and water before eating or cooking. This will help remove and any dirt or soil particles stuck to the outside of the fruit. Read more about local food and gardening: Cure Your Toxic Yard: Best Plants To Extract Lead And Other Buried Pollutants. Got a tip or a post idea for us to write about on Planet Green? Email pgtips (at) treehugger (dot) com.