''Poa annua'', or annual meadow grass (known in America more commonly as annual bluegrass or simply poa), is a widespread low-growing turfgrass in temperate climates. Notwithstanding the reference to

annual plant An annual plant is a plant that completes its life cycle, from germination to the production of seeds, within one growing season, and then dies. The length of growing seasons and period in which they take place vary according to geographical ...

in its name, perennial bio-types do exist. This grass may have originated as a

hybrid Hybrid may refer to: Science * Hybrid (biology), an offspring resulting from cross-breeding ** Hybrid grape, grape varieties produced by cross-breeding two ''Vitis'' species ** Hybridity, the property of a hybrid plant which is a union of two dif ...

between '' Poa supina'' and ''

Poa infirma ''Poa infirma'' is a species of grass known by the common names early meadow-grass and weak bluegrass. 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 ...

''.

Description

It has a slightly creeping, fibrous, rootstock. The stem grows from 15–25 cm (6-10 in.) high. It is slightly flattened, due to being folded rather than rolled. The

panicle A panicle is a much-branched inflorescence. (softcover ). Some authors distinguish it from a compound spike inflorescence, by requiring that the flowers (and fruit) be pedicellate (having a single stem per flower). The branches of a panicle are of ...

is open and triangular shaped, 5 to 7.5 cm (2 to 3 in.) long. The spikelets are stalked, awnless, 1 to 2 cm (3/8 to 3/4 in.) 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 The bow () is the forward part of the hull of a ship or boat, the point that is usually most forward when the vessel is underway. The aft end of the boat is the stern. Prow may be used as a synonym for bow or it may mean the forward-most part ...

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 A ligule (from "strap", variant of ''lingula'', from ''lingua'' "tongue") is a thin outgrowth at the junction of leaf and leafstalk of many grasses (Poaceae) and sedges. A ligule is also a strap-shaped extension of the corolla, such as that of a ...

is pointed and silvery. Compared this to Common Meadowgrass '' Poa pratensis'', which has a squared ligule, and '' Poa trivialis'', 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.

Etymology

''Poa'' is derived from the Greek name for a type of fodder grass.Gledhill, David (2008). "The Names of Plants". Cambridge University Press. (hardback), (paperback). pp 50, 308 ''Annua'' is Latin, meaning 'annual' or 'lasting a year'.

Distribution and habitat

It is a common weed of cultivation, known in the Americas as annual bluegrass. It occurs as a common constituent of lawns, where it is also often treated as a weed, and grows on waste ground. Many golf putting greens, including the

Oakmont Country Club Oakmont Country Club is a country club in the eastern United States, located mostly in Plum with only a very small portion of the property located in Oakmont, suburbs of Pittsburgh in western Pennsylvania. Established in 1903, its golf course i ...

greens, are annual bluegrass, although many courses have converted to

creeping bentgrass ''Agrostis stolonifera'' (creeping bentgrass, creeping bent, fiorin, spreading bent or carpet bentgrass) is a perennial grass species in the family Poaceae. Description ''Agrostis stolonifera'' is stoloniferous and may form mats or tufts. The ...

(''Agrostis stolonifera''). It has appeared on King George Island in the

Antarctic The Antarctic ( or , American English also or ; commonly ) is a polar region around Earth's South Pole, opposite the Arctic region around the North Pole. The Antarctic comprises the continent of Antarctica, the Kerguelen Plateau and other ...

South Shetland Islands as an

invasive species An invasive species otherwise known as an alien is an introduced organism that becomes overpopulated and harms its new environment. Although most introduced species are neutral or beneficial with respect to other species, invasive species ad ...

,Antarctic ecology: Polar invaders
The Economist, Mar 6th 2012 as well as on

Australia Australia, officially the Commonwealth of Australia, is a Sovereign state, sovereign country comprising the mainland of the Australia (continent), Australian continent, the island of Tasmania, and numerous List of islands of Australia, sma ...

's subantarctic Heard and Macquarie Islands. Poa annua.jpg, Habit Straatgras tongetje (Poa annua ligula).jpg, Ligule is silvery and pointed. Poa.annua.jpg, The panicle is open and triangular shaped Poa.annua.2.jpg, Flowers Poa annua on a footpath. 24 Oktoberplein, Utrecht, The Netherlands, May 20, 2018.jpg, Stubborn clump of ''Poa annua'' on footpath stones

References

External links

European ''Poa'' Database
* The Observers Book of Grasses, Sedges and Rushes. Frances Rose. pages 38–39
Kew gardens grass database
*Weeds friend or foe? Sally Roth. pages 86–87

{{Authority control annua Flora of Europe Flora of Africa Flora of temperate Asia Flora of tropical Asia Garden plants of Europe Lawn grasses Plants described in 1753 Taxa named by Carl Linnaeus Invasive plant species of subantarctic islands