Festuca roemeri, also known as Roemer's fescue, has 500000 seeds per pound. It is native to western North America, where it is widespread and common. It can be found in many ecosystems, from shady forests to open plains grasslands. 
Seed treatment reccommendations:  
More Info: USDA Plant Guide: https://plants.usda.gov/DocumentLibrary/factsheet/pdf/fs_fero.pdf