Does slow and steady win the race? Root growth dynamics of Arabidopsis halleri ecotypes in soils with varying trace metal element contamination

•Arabidopsis halleri plants adjust their root architecture in response to metal content in soil.•Two different development strategies were observed: dampened root growth in metalliferous and TME foraging in non-metalliferous soil.•Emplacing a thin capping layer of non-polluted substrate promotes root penetration of underlying polluted soil.