Cyperus rotondus tubers possess substances with allelopathic qualities. Some of these substances can act as synergists of plant hormones and be used for root induction in cuttings. This study aimed to shed light on the development and rooting of Eucalyptus urophylla cuttings treated with C. rotondus (nutgrass) tuber extract and IAA (indole-3-acetic acid). The experiments were conducted using a completely randomized design (0; 25; 50; 75 and 100% nutgrass extract and 0; 50; 250; 500; 750 and 1000 mg L-1 of IAA), with four repetitions per treatment and four cuttings per plot. Plantlet height, stem width and root length were measured. The greatest width and height values were recorded for the control (0% nutgrass extract and 0 mg L-1 of IAA), indicating that these substances did not contribute to the development of these variables. However, treatments of nutgrass extract up to 50% were associated with greater root length. C. rotundus extract concentrations of 53% can be used to improve root development in E. urophylla cuttings, and contribute to the production of higher quality plantlets.