In Wyoming, zone 3, I would probably discourage using PR or TTTF if you have very cold winters. TTTF and PR can suffer cold kill in very low temps. Also if you have a lot of snow cover, then TTTF will probably have snow mold every year, which can also kill areas of turf. Fine fescues are very hardy once established, requiring little in the way of fertilizer or water but dormancy can be expected in hot, dry summers. If you go that route then I would probably use mostly creeping red fescue as it spreads, but be sure and get a named cultivar, not boreal which is actually common CRF. Kentucky bluegrass is also a good choice, but for your area you would need to choose a cultivar(s) that have very good spring green up and good cold tolerance. Many cultivars that do very well in lower latitudes will be dormant well into spring in your climate.

-Can I mix a tall fescue mix with a fine fescue mix for more diversity or would this create all sorts of problems?

You can mix most grasses, but you may not like how they look, and again, TF might have issues with cold kill/snow mold.

-Will the KBG eventually out compete the Tall Fescues in the Defiance mix?

No, but any areas of TF that die will probably fill in with KBG and or weeds, so over time you might have a predominantly KBG lawn.

-Is it a problem or a benefit to have the perennial rye mixed in with the fine fescues? I have read perennial rye needs more water and fertilizer than fine fescues.

Most seed mixes have some PR in them. The main reason is because it acts as a nurse grass, and makes consumers happy because they see germination in such short order. Unfortunately PR grows very fast when mature, and will not give you a consistent lawn. It does require more water and fertilzer than CRF too, as well as more frequent mowing.

Wow, thanks for your great answer. Sounds like I should go for a fine fescue mix like the one from Wildflower farms. Is there any other type of grass that would complement a fine fescue blend for more diversity?

Since you just installed a sprinkler, that means you have long lines of trenches dug out between the sprinkler heads. One thing most people do not account for is settling. The soil along those trenches will settle for 3 years. In the end you will have low spots along those lines which make it harder to mow and possibly will collect water. If you have not left a mound over top of those trenches, you will have the low spots. It should be mounded about 1/2 to 3/4 inch along the lines.

Another consideration for a lawn is to go with native prairie grasses. Some to consider are blue grama and a variety of wheatgrasses which grow well in WY. Once established these need little water and only monthly mowing. Color is deep green, and the texture is fine like the other grasses you are considering. When mowed monthly these make a great lawn for low traffic.

Here is a picture of one such lawn in Salt Lake City. The owner is bpgreen who occasionally still peeks into the GardenWeb forums. The clover at the bottom is strawberry clover and was used on purpose to help with soil fertility.

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