In phytoextraction (also phytoaccumulation, phytosequesteration or phytoabsorption) plants carry radioactive waste from the root system to the vascular tissue and become concentrated in the biomass of shoots. It is a technique that removes radionuclides without destroying the soil structure, with minimal impact on soil fertility and valid for large areas with a low level of radioactivity. Its efficiency is evaluated through bioaccumulation coefficient (BC) or total removal of radionuclides per m, and is proven to attract cesium-137, strontium-90, technetium-99, cerium-144, plutonium-240, americium-241, neptunium-237 and various radioisotopes of thorium and radium. By contrast, it requires large biomass production in short periods of time.
Species like common heather or amaranths are able to concentrate cesium-137, the most abundant radionuclide in the Chernobyl Exclusion Zone. In this region of Ukraine, mustard greens could remove up to 22% of average levels of cesium activity in a single growing season. In the same way, bok choy and mustard greens can concentrate 100 times more uranium than other species.