Resumo. The lack of knowledge of management in the application of yerba mate is the reason for the present study, given the economic importance of this crop for family farming, the economy and also the culture in the southern region of Brazil. The objective of this work was to evaluate the effects of winter cover species on the morphophysiological characteristics of yerba mate seedlings. The experimental design was laid out in randomized blocks with four replicates. The weed species used were Avena strigosa, Lolium multiflorum, Vicia sativa, Raphanus sativus, Lupinus albus, Axonopus catharinensis, the consortium between A. strigosa and V. sativa, and the control treatment without cover. Physiological (photosynthesis, stomatal conductance, transpiration, internal CO2 concentration, water use efficiency, carboxylative efficiency, and chlorophyll) and morphological (plant height, stem diameter, leaf area, shoot and of root dry matter, in addition to cover dry matter) were evaluated. There was competition between the crop and the cover plants for the factors of light and water, and the control without cultivation did not affect the morphophysiological characteristics of yerba mate. The species A. catharinensis proved to be the best cover plant because it competed less with yerba mate. The growth and development of yerba mate were affected by the presence of A. strigosa.