Each species offers something to compliment or fill in where the others may fall short. That's why most cool season grasses - what are grown in the northern tier of the country - are blends or mixes, as no single species will provide a uniform look throughout the year.

KBG needs sun. It is also very cold tolerant and holds up to foot traffic well. But will dry out and go dormant with the heat of summer unless routinely watered. Also prone to thatch development and is susceptible to disease issues if in an area with wet winters and mild, damp springs. Therefore NOT recommended for the PNW. Also takes longer to germinate than other species.

Perennial rye also need sun. Will thin out in much shade. But it is quite drought tolerant and needs less summer irrigation to prevent dormancy but still requires routine watering in summer. Germinates rapidly and has increased disease resistance compared to the KBG. Highly tolerant to wear and foot traffic.

Fine fescues are more shade tolerant. They are also more drought tolerant than KBG but do not hold up as well to wear or heavy foot traffic.

Tall fescue is both sun and shade tolerant and because of a deep root system, tends to be very drought tolerant. But it has a coarse texture and doesn't blend well with the finer textured fescues and ryes and is also prone to diseases associated with cool, wet winters.