Native grasslands provide a multitude of benefits to society including forage production, wildlife habitat, and nutrient and CO2 sequestration. There has been continuing interest in restoring grasslands to maximize these multiple benefits within the conservation community. There are presently many ongoing prairie restoration projects, and many more are being started throughout Iowa. Warm-season grasses such as big bluestem, indian grass, switchgrass, little bluestem, or side-oats grama often dominate prairies. In western Iowa, all five of these species are dominant, at least in some patches of grassland. Diversity is what most people are most concerned with when they restore or reconstruct prairie. However, species diversity in prairies is mainly from various forbs. Most prairie restorations become heavily dominated by one or a few grass species without a wide diversity of legumes and forbs. We suggest that understanding how dominant warm-season grasses suppress total plant diversity and prevent weed invasions is a key issue for developing better restoration plans.