Fagopyrum esculentum is highly nutritious due to its proteins of high biological value and high fiber content. Its most relevant property is nonetheless its antioxidant activity, provided by the presence of flavonoids. It is an important pseudocereal in agriculture, animal production, and human food. The objective of study was to evaluate the grain yield and flavonoid production of Fagopyrum esculentum cultivars as a function of base saturation. The experiment was carried out in a greenhouse, in a completely randomized design with four replicates. Treatments were represented by cultivars IPR 91 and IPR 92 and five base saturation levels (9, 31, 53, 75, and 97 %), in a factorial arrangement (2 × 5). Agronomic attributes and total-flavonoid and rutin contents and production were evaluated. Subsequently, the data were subjected to statistical analysis. Base saturation does not affect flavonoid production. However, base saturation influences shoot dry matter yield (maximum at 62.0% base saturation) and grain yield (maximum at 9.00%) in IPR 92. The higher-yielding cultivar is IPR 92. This is the first scientific report of base saturation in the species.