Phytoremediation. I know, it’s a mouthful. In a butternut shell, it is the use of plants to clean up contaminated environments. Plants from all around the kingdom—mushrooms, grasses, shrubs and trees—can pick up a mop and play air guitar to the tune of “heavy-metal” clean up.
Trees are spectacular at contaminant degredation because they are big, woody plants that grow quickly. And what’s even more interesting is that some trees pegged as “pesky” in some situations actually turn out to be the best at absorbing harmful materials. Trees can clean up in several ways: by uptaking, storing, and degrading contaminants within their tissues, or else by transforming and releasing them into the air; or else through symbiotic associations with soil microbes to degrade the contaminants underground.
Poplar trees have somewhat of a bad rap because they are pioneer species that grow quickly and are often short lived. But because of their well-designed root system, they have amazing absorption power that has been widely studied for effectively cleaning up chlorinated solvents and petroleum hydrocarbons, and in contaminated water, they have done well to absorb lead. (Red maples, another quick growing tree, also work well in tandem with hybrid poplars for uptaking leachates.)
Willow trees like wet feet, the saying goes, so you’ll often find them along shorelines or in wet areas. They, too, have powerful root systems that can sometimes be bothersome when growing near septic systems or other underground infrastructure. But the incredible absorption of their roots can uptake heavy metals like cadmium, nickel and lead, and even mixed heavy metals like diesel-fuel.