These grasses add texture and help stabilize the soil. The label on your mix should list every species contained in the mix. Try to find a good mix for your region. Try to rid the meadow of weeds before planting. Weeds are the most common reason for the failure of a wildflower meadow.
Solarization usually does a good job of ridding the soil of weeds.
See Soil Solarization . Till and prepare the soil as you would for any seedbed, then apply the seeds at twice the rate recommended on the package. To facilitate even spreading, mix seeds with equal portions of clean river sand. Keep the seedlings moist and weed diligently. Cut to 6 inches high in late winter to prevent invasion by woody plants and to help disperse flower and grass seeds.