There are 3 cool season grasses that make good turf, bluegrasses, perennial ryes, and fescues. There are hundreds of bluegrasses, almost that many perennial ryes, and a hundred or so fescues to choose from. Since there are pluses and minuses for every grass species, a proper mix of these species takes advantage of the good points and disguises the weaknesses.  

Over the years, Ideal Sod has reviewed hendreds of theses grasses, and grown many, in the ongoing process of having the best performing sod. Seed companies have spent millions, if not billions, of dollars on the search for the perfect grass. No one has found it yet so until then, a proper mix out performs in every situation.