Thousands of different types of grass can be found in North America, but only a few species are used in home lawns. When seeding a lawn, it is important to choose the species, or mix of species that will grow best in that particular environment.Each turfgrass species has a number of cultivars, varieties or hybrids, each of which are slightly different genetically. Most grass seed mixes consist of a variety of species and cultivars in order to maintain good biodiversity within the lawn. Good biodiversity generally translates into a healthier lawn that is able to tolerate diseases, and flourish in a wider range of environmental conditions.