Poplars accumulate high B concentrations and are thus used for the phytomanagement of B contaminated soils. Here, we performed pot experiments in which Populus nigra x euramericana were grown on a substrate with B concentrations ranging from 13 to 280 mg kg^-1 as H₃BO₃. Salix viminalis, Brassica juncea, and Lupinus albus were grown under some growing conditions for comparison. Poplar growth was unaffected at soil B treatment levels up to 93 mg kg^-1. Growth was progressively reduced at levels of 168 and 280 mg kg^-1. None of the other species survived at these substrate B levels. At leaf B concentrations <900 mg kg^-1 only <10% of the poplar leaf area showed signs of toxicity. Neutron radiography revealed that chlorotic leaf tissues had B concentrations of 1000-2000 mg kg^-1, while necrotic tissues had >2000 mg kg^-1. Average B concentrations of up to 3500 mg kg-1 were found in leaves, while spots within leaves had concentrations >7000 mg kg^-1, showing that B accumulation in leaf tissue continued even after the onset of necrosis. The B accumulation ability of P. nigra x euramericana is associated with B hypertolerance in the living tissue and storage of B in dead leaf tissue.