Poa pratensis, commonly known as Kentucky bluegrass, smooth meadow-grass, or common meadow-grass, is a perennial species of grass native to Europe, Asia, North America, and northern Africa. Poa pratensis forms a valuable pasture plant, characteristic of well-drained, fertile soil. It is also used for making lawns in parks and gardens and is common in cool moist climates like the northeastern United States.
Poa pratensis was one of the many species described by Carl Linnaeus in his landmark work Species Plantarum in 1753. Poa is Greek for fodder and pratensis is Latin for meadow. The name Kentucky bluegrass derives from its flower heads, which are blue when the plant is allowed to grow to its natural height of two to three feet.
There are two ill-defined subspecies:
Poa pratensis is a herbaceous perennial plant 30–70 centimetres (12–28 in) tall. The leaves have boat-shaped tips, narrowly linear, up to 20 centimetres (8 in) long and 3–5 millimetres (0.12–0.20 in) broad, smooth or slightly roughened, with a rounded to truncate ligule 1–2 millimetres (0.039–0.079 in) long. The conical panicle is 5–20 centimetres (2–8 in) long, with 3 to 5 branches in the basal whorls; the oval spikelets are 3–6 millimetres (0.12–0.24 in) long with 2 to 5 florets, and are purplish-green or grey. They are in flower from May to July, compared to annual meadowgrass (Poa annua) which is in flower for eight months of the year. Poa pratensis has a fairly prominent mid-vein (center of the blade).
The ligule is extremely short and square ended, making a contrast with Annual Meadowgrass (Poa annua) and Rough Meadowgrass (Poa trivialis) in which it is silvery and pointed. The Kentucky bluegrass is a dark green compared to the apple green color of poa annua and poa trivialis.
This species is among the foodplants of the caterpillars of the Meadow Brown (Maniola jurtina) and Gatekeeper (Pyronia tithonus) butterflies; the Common Sun Beetle (Amara aenea) (adults feed on the developing seeds), Eupelix cuspidata of the leafhopper family, and Myrmus miriformis, a grassbug (feeds on young blades and developing seeds).
Cultivation and production
Bella Bluegrass is a cultivar produced through the breeding program at the University of Nebraska. It is unique among bluegrasses for its vegetative reproduction, slow growth habit, a short leaf.
Very dark green, compact growth habit. 'Midnight' has stood out in National Turfgrass Evaluation Program trials for 20 years. It has the distinction of heading its own class of compact-type hybrid bluegrasses known as 'Midnight-type' (crosses with 'Midnight' as a parent).
Granite is very dark green, dense and fine leaved, with exceptional turf quality and wear tolerance. It is an excellent summer performer under severe summer stress, and will persist indefinitely under demanding turfgrass conditions. Granite is a low growing cultivar that requires less frequent mowing than most other bluegrasses. Granite has shown high resistance to wilting and excellent drought tolerance for reduced water requirements.
4-Season is known for being the first variety of Kentucky Bluegrass to perform in all four seasons of the year. It consistently rates high among top performing varieties for turf density. It establishes quickly to provide a uniform turf. It is known for coming out from spring snow with a green and growing condition. 
Award is one of the ideal fairway bluegrasses, as it is able to perform at mowing down to 1/2 inch. This variety is great for golf courses and provides a dark green, dense turf that crowds out weeds. It excels at a variety of maintenance levels, and was among the top 2 varieties for unirrigated, low maintenance lawns in university trials. It scores high in NTEP trials for close mow tolerance, summer density, fall color, and turf quality. It has great disease resistance as well. 
Nu Destiny is known for its superior resistance to summer patch, necrotic ring spot, leaf spot, red thread, Microdochium pink snow mold, brown patch, spring melting out, anthracnose, stem rust, dollar spot, and stripe smut. It has great resistance against bluegrass billbug as well. It produces a strong, thick, dark green turf that naturally crowds out weeds. Its vigorous rhizome system helps it hold up against wear and tear better than other varieties. It places with the top varieties for sports shear resistance. It also holds up well in shady areas. 
Hybridization with Poa arachnifera
- Published: June 03, 1993 (1993-06-03). "What Makes Kentucky's Bluegrass Blue – New York Times – June 3, 1993". Query.nytimes.com. Retrieved 2012-12-23.
- Natural England description on website
- Shearman; Robert C. ; et al. "US Patent Application Poa pratensis L. named 'NE-KYB-05-001'". US Patent Office. Retrieved 27 March 2013.
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- European Poa Database
- Horticultural information on this turfgrass; growing it in the home garden
- The Observers Book of Grasses, Sedges and Rushes. Frances Rose. pages 42–43
- Kew gardens grass database