I wondered the same. A quick Google turned up the fact, "Oh, yeah, that's been investigated and there ARE options." Chinese brake fern (Pteris vittata) seems t

I wondered the same. A quick Google turned up the fact, "Oh, yeah, that's been investigated and there ARE options." Chinese brake fern (Pteris vittata) seems to be a candidate: https://www.newsweek.com/plant-arsenic-chemical-highly-toxic-humans-1428988 https://www.newsweek.com/plant-arsenic-chemical-highly-toxic... Plants as Useful Vectors to Reduce Environmental Toxic Arsenic Contenthttps://www.ncbi.nlm.nih.gov/pmc/articles/PMC3913097/ https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3913097/ I do have to wonder if we would find ourselves inviting invasive species with such an exercise. But on the other hand, the goal is to "grow'em, burn'em, and carefully dispose of the ash" so maybe that concern is manageable.