The main goal of this research was to evaluate the growth of nimblewill (Muhlenbergia schreberi), an emerging threat to forage grass. Our initial experiment was arranged in a completely randomized design, with 17 treatments (i.e., weeks) and 4 repetitions. Seventeen growth evaluations (i.e., treatments) were carried out every 7 days, totaling a 119-day cycle, followed by an analysis of the variables such as stolon number, length, number of leaves, dry matter, biological productivity, growth rate, and relative growth rate. A second experiment was conducted over a 5-week period to compare the growth variable between nimblewill plants and pastures. For all variables, the results showed that the weed grass developed slowly within the first 5 weeks after germination, indicating that this would be the best time to implement a chemical or cultural control measure. It was also observed that cultures with a rapid growth in the first 5 weeks after emergence could easily suppress weed growth. At the end of the experiment, stabilization of all variables was observed. However, additional observations are required to obtain more accurate results.