Cotyledon reserves are the prime source of nutrition for early heterotrophic seedling growth and development. Larger seeds have more nutrient reserves and support better germination, while smaller seeds are physiologically more active and show rapid emergence and growth during early seedling stage. Thus, when investigating genes that control early seedling growth and development, it is important to assess the extent to which genes that control seed size also control, indirectly, heterotrophic seedlings growth. If the latter set of genes exerts a significant control on early growth, then seed size should be considered as a covariate in the genetic analysis of early growth. Seed size effects on early seedling growth should be investigated within the same genotype. One possibility is to control seed size by effecting growth conditions, or by removing one cotyledon. However, parental environmental effects and wounding can bias the results. Instead, we generated F1 seeds from reciprocal crosses between the landrace G19833 (0.56 g/seed) and the wild accession G23419 (0.18 g/seed) of common bean (Phaseolus vulgaris L.) under identical environmental conditions. Seeds resulting from artificial cross pollinizations attain the same weight/size as those resulting from selfing events in the maternal plant, regardless of the genetic makeup of the paternal donor. These reciprocal F1s differ in seed size as the parental genotypes, but have the same genotype. Curve fitting approaches have been used to compare the dynamic growth phenotypes of the reciprocal F1s. These results will be used for functional mapping of QTL controlling early seedling growth.