Dominance of warm-season grasses modulates tallgrass prairie ecosystem structure (e.g., community composition) and function (e.g., net primary production). Reintroduction of these grasses is a widespread practice to conserve soil, improve water quality, and restore tallgrass prairie ecosystems degraded from human land use changes such as agriculture. Seed sources for re-introduction of dominant prairie grass species include non-cultivar (collected from local remnant prairie) and selected (cultivar) populations. The overall objective of this study was to quantify whether intraspecific variation in developing root systems exists between population sources (non-cultivar and cultivar) of three dominant grasses used in restorations: Andropogon gerardii (big bluestem), Sorghastrum nutans (Indiangrass), and Schizachyrium scoparium (little bluestem). Non-cultivar and cultivar population sources of each species were isolated and grown in 7.62-cm diameter x 20 cm depth PVC cores inserted in a newly established experimental tallgrass prairie restoration at the Konza Prairie Biological Station (KPBS), Manhattan, KS. Non-cultivar source population seeds were collected from local remnant ecotypes at KPBS and recommended cultivar seeds were acquired from the USDA. I measured above- and below-ground net primary production (ANPP and BNPP), root architecture (root length, surface area, and volume), root tissue quality, and plant available inorganic nitrogen in each core at the end of the first growing season. Cultivars tended to have greater root length, surface area, and volume than non-cultivars for both S. nutans and S. scoparium . Two important soil resources, available inorganic N and water, were present in lower amounts in soil proximal to roots of cultivars than non-cultivars. Additionally, soil nitrate was negatively correlated with root volume in S. nutans and A. gerardii cultivars. Conversely, there were no correlations between soil N and root architecture among non-cultivars. While cultivars had greater below-ground net primary productivity (BNPP) than non-cultivars, this was not reflected above-ground, where ANPP was not different between cultivars and non-cultivars. There were no intraspecific differences in percent N, resulting in no difference in root tissue quality among species or sources. Overall, my results suggest there are some differences between cultivar and non-cultivar sources of the dominant prairie grasses used in restoration. These phenotypic differences may scale up to affect community and ecosystem properties, and consequently should be taken into consideration in the context of setting restoration goals and objectives.