The aim of this study was to assess the responses of five alfalfa genotypes to summer drought under field conditions. Landraces from oases, Adis1 and Tata2, others, Demnate208 and Demnate206, from the Moroccan Atlas Mountains and Siriver, were grown at the experimental station of INRA. The plants were subjected to 100% ETc (crop potential evapotranspiration) as control, 75% as moderate and 50% as severe drought. Growth, water parameters and physiological responses were assessed. Results showed that stress significantly reduced plant dry biomass, height, stomatal conductance and increased water productivity (WP) in all of tested cultivars with variation between them. The highest biomass reductions were registered under 50% ETc and were more pronounced in Demnate208 (exceeded 50%), than in Adis1 (did not reach 37%). Therefore, we qualified the latter as more tolerant and the former as less tolerant. Adis1 presented high WP (0.11 kg m⁻³). It accumulated the highest proline, sugars and K⁺ under stress. Siriver presented intermediate behaviour. For all of the assessed parameters, we noted high consistency between growth and water parameters and proline, sugars and K⁺ accumulations, particularly in Adis1. Thus, we suggested that these compatible solutes could be involved in the alfalfa drought tolerance mechanism. Copyright © 2017 John Wiley & Sons, Ltd.