Poa annua
Encyclopedia
Poa annua, or annual meadow grass (known in America more commonly as annual bluegrass), is a widespread low-growing turfgrass in temperate climates. Though P. annua is commonly considered a solely annual plant
Annual plant
An annual plant is a plant that usually germinates, flowers, and dies in a year or season. True annuals will only live longer than a year if they are prevented from setting seed...

 due to its name, perennial bio-types do exist. 'Poa' is Greek for fodder. It is one of the sweetest grasses for green fodder, but less useful than hay
Hay
Hay is grass, legumes or other herbaceous plants that have been cut, dried, and stored for use as animal fodder, particularly for grazing livestock such as cattle, horses, goats, and sheep. Hay is also fed to pets such as rabbits and guinea pigs...

. This grass may have originated as a hybrid between Poa supina and Poa infirma
Poa infirma
Poa infirma is a species of grass known by the common names weak bluegrass and early meadowgrass. It was first described from a specimen found in Colombia, but it is actually an introduced species in the Americas and is native to Europe. It grows in many types of habitat, including disturbed areas...

.

It has a slightly creeping, fibrous, rootstock. The stem grows from 15–25 cm high. It is slightly flattened, due to being folded rather than rolled.

The panicle
Panicle
A panicle is a compound raceme, a loose, much-branched indeterminate inflorescence with pedicellate flowers attached along the secondary branches; in other words, a branched cluster of flowers in which the branches are racemes....

 is open and triangular shaped, 5 to 7.5 cm long. The spikelets are stalked, awnless, 1 to 2 cm long when flowering, and loosely arranged on delicate paired or spreading branches. Sometimes they are tinged purple.

The vivid green leaves are short and blunt at the tips, shaped like the prow of a small canoe. They are soft and drooping. Long sheaths clasp the stem. The leaves are smooth above and below, with finely serrated edges. Occasionally the leaves are serrated transversely.

The ligule
Ligule
A ligule — is a thin outgrowth at the junction of leaf and leafstalk of many grasses and sedges or a strap-shaped corolla, such as that of a ray floret in plants in the daisy family....

 is pointed and silvery. Compared this to Common Meadowgrass Poa pratensis, which has a squared ligule, and Poa trivialis
Poa trivialis
Poa trivialis , is a perennial plant, and is regarded in the USA as an ornamental plant and is of the Poa family.-Description:...

, which has a pointed, but less silvery ligule.

The leaves are smooth above and below, with finely serrated edges. Occasionally the leaves are serrated transversely.

It is in flower all year around except for severe winters. The seeds ripen and are deposited 8 months of the year. The plant grows rapidly from seed, flowering within 6 weeks, seeding and then dying.

It is a common weed
Weed
A weed in a general sense is a plant that is considered by the user of the term to be a nuisance, and normally applied to unwanted plants in human-controlled settings, especially farm fields and gardens, but also lawns, parks, woods, and other areas. More specifically, the term is often used to...

 of cultivation, known in the Americas as annual bluegrass. It occurs as a common constituent of lawn
Lawn
A lawn is an area of aesthetic and recreational land planted with grasses or other durable plants, which usually are maintained at a low and consistent height. Low ornamental meadows in natural landscaping styles are a contemporary option of a lawn...

s, where it is also often treated as a weed
Weed
A weed in a general sense is a plant that is considered by the user of the term to be a nuisance, and normally applied to unwanted plants in human-controlled settings, especially farm fields and gardens, but also lawns, parks, woods, and other areas. More specifically, the term is often used to...

, and grows on waste ground. However, it is sometimes the most suitable lawn grass for many sites, and can form most of the entire grass sward in some lawns. On lawns it grows better in rich soils, but is usually small enough to be overlooked. It does not compete with other plants. Many golf putting greens, including the famously fast Oakmont Country Club
Oakmont Country Club
Oakmont Country Club is a country club and the "oldest top-ranked golf course in the U. S.", in the Pittsburgh suburbs of Plum and Oakmont, Pennsylvania, USA. The Pennsylvania Turnpike separates the eastern seven holes from the rest of the course....

 greens, are planted with this grass, although many courses have converted to bentgrass (Agrostis spp.).
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