Ten plants, were identified for the greenhouse study based on aesthetic value, a documented history of removing pesticides from soils and their value as a wildlife habitat.

Blue flag iris was the clear winner, able to reduce levels of the commonly used insecticide chlorpyriphos by 76 percent and levels of the widely used fungicide chlorothalonil by 94 percent in soil after three months of growth. Other plants that performed well in the greenhouse trials included eastern gama grass, a common resident of wetlands in the eastern United States, and big blue stem, one of the chief plants of the tallgrass prairie.

Successful candidates identified in the greenhouse study had the largest root systems, which provided surface area for the plants to absorb pesticides, or hold them in place in the soil while they were broken down by microorganisms. Large roots also open the soil to allow runoff to sink into the ground instead of travelling to waterways, creating a “pesticide sink.”