Getting the Lead Out (phytoremediation)Posted: November 6, 2015
When we purchased our home, it was the land I valued as the key asset. Our first soil test brought the stunning news that lead in the soil averaged 480 parts per million, a level classified as “move garden to uncontaminated soil.” We got busy researching, and learned that Helianthus annus, the common sunflower, will draw the lead out of the soil.
With that shot of enthusiasm we got to work amending our land. In the autumn of 2013 we sheet mulched a large space in our sun-drenched front yard; we call this the mandala garden. On top of a thick layer of cardboard, we piled rock dust, aged manure, chopped leaves and perennials, and clean top soil: the pile was about 14″ high.
By the spring of 2014 we tested the soil again and this area – far enough away from our house to be out of reach of lead paint chips – showed a level of 280; better but still too high to grow leafy or root vegetables.
This spring our soil test showed 215 ppm, which is classified as a “slight” contamination but still is a major step forward. We continue to add compost, but we grew fruiting vegetables this summer.
And some sunflowers just for good measure.