Agricultural production and it’s crop breeding programs is mainly oriented towards above-ground biomass. Nevertheless, phenotypic plasticity of the root system can improve resilience to environmental stress and ensure crop production under detrimental conditions. The ability to alter phenotypic root traits in response to the environment can be integrated in breeding programs when the plasticity of individual root traits can be quantified. The relative distance plasticity index (RDPI) is a useful and easy to use index for the quantification of the plasticity of root traits. It can be applied in laboratory as well as in field conditions.