High elevation turfgrass sites (5000 ft. and above) are best suited with cool season grasses for lawns. These include Kentucky bluegrass (KBG), perennial ryegrass and fine leaf fescue. When buying lawn seed for these elevations, the seed is often packaged as a mixture. The mixture includes two or more different species of grass. The most common mixture for high elevation locations include a three-way mixture of KBG, perennial ryegrass and fine leaf fescue. Tall fescue is included in mixtures only in special cases and is best planted alone.

The reason that these species are mixed together is that each grass plays a special part in the course of the life of the lawn. Typical mixtures my include 60-75% KBG seed, 10-15% perennial ryegrass seed and 15-20% creeping red fescue seed. The intention is as follows.

Kentucky bluegrass (KBG) Poa pratensis
The KBG is intended to be the permanent and predominate species. It has the advantage of producing underground runners (rhizomes). Rhizomes allow the turf to become thick, crowding out weeds and serving as a growing point for the grass to regrow when it is injured, diseased or undergoes long periods of drought.

Perennial ryegrass Lolium perenne
The perennial ryegrass serves as a "nurse crop" until the other two species get going. The quick germination and emergence of perennial ryegrass binds the soil and makes a quick and thin lawn while the other grasses germinate slower and grow lazily at first. The ryegrass has thin leaves so it is compatible with the other two grasses (KBG and creeping red fescue). Planting too much perennial ryegrass will cause too much competition with the other grasses. The resultant lawn will stay a "ryegrass lawn" for a long time if the mixture contains over 15% perennial ryegrass. The turf eventually thins out from some perturbation that eventually affects the ryegrass.

Creeping red fescue Festuca rubra
Creeping red fescue is one of the "fine fescue" groups of turf fescues. It produces short underground rhizomes. The leaves are very thin. Creeping red fescue is shade tolerant. That's why it is included in the mixture. The creeping red fescue will eventually be crowded out by the perennial ryegrass and KBG in areas of high sunlight, but it will stay in the shaded areas. Creeping red fescue is usually 20-30% of the seed mixture by weight. Remember, tall fescue is almost never included in mixtures with these other grasses. This is because tall fescue grows best when planted alone.

There are some special cases when a thinner leaf tall fescue can be mixed with a non-aggressive KBG. Otherwise, avoid that situation if at all possible.