Seed is the least expensive way to establish a cool-season lawn of either fescue or bluegrass. Laying sod forms an instant carpet of foliage for a pleasing display. An evenly moist soil that drains well after rains or irrigation is needed. Summer temperatures consistently above 85 degrees tend to stress both these grass types, leading to an increased need of water. Otherwise, the grasses become dormant and change from green to brown.
Kentucky bluegrass is the botanical species Poa pratensis. Of the fescue types most widely used for lawns, tall fescue dominates and is known botanically as Festuca arundinacea. Another species known as tall fescue is Festuca elatior. Other fescues encountered for lawn use are red fescue (Festuca rubra) and hard fescue (Festuca longifolia).
Kentucky bluegrass blades are narrow and create an airy, fine texture to a lawn. It's a dark-green grass with shallow root system and leaves that are folded when in bud stage. The roots are creeping rhizomes and repair any bare openings in the lawn, readily making a dense carpet. Tall fescue has slightly broader leaf blades than bluegrass and forms a coarser lawn with uniform appearance. It naturally is a dark-green grass with extensive fibrous root system. The leaves are rolled in the bud. It forms bunches rather than creeping stems and "bald" areas may develop in lawns, according to the University of California.
Slight variations in tolerance by these cool-season grasses warrant their use in different capacities across various regions and climates. Kentucky bluegrass, when compared to tall fescue, is more adaptable to retaining green color in chillier winter temperatures and recovering after a severe injury or physical damage to the turf carpet. By contrast, tall fescue is slightly better in shady conditions, recovering after moderate wear from foot traffic, slightly better tolerance to drought, soil and air salinity and summertime heat. Bluegrass is the better choice for high elevation or chilly summer/colder winter areas of the northern U.S. or Canada.
According to the University of California, Kentucky bluegrass has a higher maintenance cost and requires more effort that tall fescue lawns. Moreover, tall fescue works well if you choose to mow your lawn at high settings, over 3 inches, for example. Disease occurrences are more likely in Kentucky bluegrass lawns than tall fescue lawns and bluegrass tends to need high levels of nitrogen in the soil to grow and look its best.
While these two grass types have varying tolerance when compared head-to-head, overall they prosper in roughly the same growing conditions. Neither grows densely in shady spots in the yard; red fescue is best for a shadier area. Dry soils and summer heat stress the plants. Irrigation in summer is necessary to keep the blades green. Kentucky bluegrass makes a lush, soft-looking turf that is best not walked on heavily; fescues are much better to use on fields earmarked for active children or mild athletic activity.