SUMMARYTwo grass species,Holcus lanatusandDeschampsia flexuosa, were grown in soil containing available nitrogen at 4 μg g−1(‘Low N’) or 58 μg g−1(‘High N’), in a controlled environment. Water was supplied via an auto‐irrigation system, which also minimized the vertical redistribution of soil nutrients, particularly NO3−. Growth, root morphology and distribution, and N uptake were measured during a 70‐day period.H. lanatusproduced more dry matter thanD.flexuosain the high N treatment. Yields were similar in both species in the low N treatment. The growth ofH. lanatusin the low N treatment was not limited by a complete exhaustion of soil N. Root density ofH. lanatuswas likely to have been inadequate to allow this species to attain its maximum potential N‐inflow rate. Thus, N uptake per plant and dry matter production were restricted. The growth ofD.flexuosawas not limited by the low N treatment, compared with that in the high N treatment. This was attributed to its low maximum potential relative growth rate and, hence, its low demand for N compared withH. lanatus, rather than to any major ‘compensatory’ adjustments in root morphology o