What you’re looking at is a sponge. Well, sort of. It’s not the type of thing you’d find in your kitchen sink, but a pollution sponge—a plant that sucks up heavy metals and other contaminants from dangerously poisonous soil. And while it may look perfectly friendly and inviting, this Alpine penny-cress grows in sterile clay packed with lead, cadmium, and toxic levels of zinc. It’s not what you’d regard as an “edible weed” by any stretch.
Plants like this are now being studied as a means of sopping up the mess caused by a centuries-long operation—one begun by the Romans in what is now southern France, and finally shut down in 1992. The legacy the mine left behind has rendered much of the soil inhospitable for plant species—all save this penny-cress, and two others varieties. These miraculous survivors, which suck up heavy metals and store them in vacuoles, may be an environmentally friendly solution to an environmentally disastrous situation. All that thanks to a little process known as phytoextraction.