The objective of this work was to evaluate the effects of growth management at different times of uniformization in plants of Brachiaria brizantha cv. BRS Paiaguás, associated with application of boron doses, quantifying the effects in the flowering and emission of reproductive tillers, and in the quantity and quality of pollen. The trial was conducted at Embrapa Gado de Corte in Campo Grande, MS, Brazil, in the 2018/2019 harvest, using a randomized block design with four replications, organized in a 3x5 factorial scheme, in which the three plant uniformization seasons consisted of, non-standardized (free growth), standardized at 67 days or 81 days after sowing, and the applications of five doses of boron, zero (control), 1, 2, 4 and 8 kg ha-1. The different doses of boron applied did not influence flowering, as well as reproductive tillering and the quantity and viability of pollen grains. The standardization management of the plants prolonged the flowering period of the cultivar. Plants kept in free growth showed greater quantity and viability of pollen grains, while the other uniformity times reduced the viability of pollen grains. Environmental factors such as precipitation and temperature interfered with reproductive tillering and viability of pollen grains.