Poa

Poa
Poa annua (Annual Meadow-grass)
Scientific classification
Kingdom:	Plantae
(unranked):	Angiosperms
(unranked):	Monocots
(unranked):	Commelinids
Order:	Poales
Family:	Poaceae
Genus:	Poa L.
Species
About 500 species, including: Poa abbreviata - Short Bluegrass Poa alpigena - Northern Meadow-grass Poa alpina - Alpine Meadow-grass Poa alsodes - Grove Bluegrass Poa angustifolia - Narrow-leaved Meadow-grass Poa annua - Annual Meadow-grass, Annual Bluegrass Poa arachnifera - Texas Bluegrass Poa arctica - Arctic Meadow-grass Poa badensis Poa balfourii - a mountain species with large blue spikelets, ligule 3mm long Poa bulbosa - Bulbous Meadow-grass Poa cita - Silver Tussock Poa compressa - Flattened Meadow-grass Poa chaixii - Broad-leaved Meadow-grass Poa chathamica Poa colensoi - Blue Tussock Poa douglasii - Douglas Bluegrass Poa dura Poa flabellata Poa flexuosa - Wavy Meadow-grass Poa glauca - Glaucous Meadow-grass, a mountain species with hairy lemmas Poa humilis - Spreading Meadow grass - has hairy lemma Poa infirma - Early Meadow-grass Poa iridifolia Poa labillardieri Poa nemoralis - Wood Meadow-grass Poa palustris - Swamp Meadow-grass Poa pratensis - Smooth Meadow-grass, Kentucky bluegrass Poa secunda - Sandberg's Bluegrass Poa subcaerulea - Spreading Meadow-grass Poa supina - Creeping Meadow-grass Poa trivialis - Rough Meadow-grass

Stem showing why it's called "bluegrass." The seed pods go from green to purplish blue to brown. During the purplish blue phase the seed stems have a navy blue coating.

Rough Meadow-grass Poa trivialis showing the ligule structure

Poa is a genus of about 500 species of grasses, native to the temperate regions of both hemispheres. Common names include meadow-grass (mainly Europe and Asia), bluegrass (mainly North America), tussock (some New Zealand species), and speargrass. 'Poa' is greek for fodder.

Bluegrass, which has green leaves, derives its name from the seed heads which are blue when the plant is allowed to grow to its natural height of two to three feet.^[1]

One species, Smooth Meadow-grass Poa pratensis, is the type species of the family Poaceae.

The genus Poa includes both annual and perennial species. Most are monoecious, but a few are dioecious (separate male and female plants). The leaves are narrow, folded or flat, sometimes bristled, and with the basal sheath flattened or sometimes thickened, with a blunt or hooded apex and membranaceous ligule.

Cultivation and uses

Many of the species are important pasture plants, used extensively by grazing livestock. Kentucky bluegrass (Poa pratensis) is the most extensively used cool-season grass used in lawns, sports fields, and golf courses in the United States.^[2] Annual bluegrass (Poa annua) can sometimes be considered a weed.^[3]
Since the 1950s/early 1960s 90 percent of the seed has been produced on farms in Idaho, Oregon and Washington.^[4]

Some of the Poa species are popular for gardens and for landscaping in New Zealand.

Insect foodplant

Lepidoptera whose caterpillars feed on Poa include:

• Common Wood-Nymph, Cercyonis pegala
• Hobomok Skipper, Poanes hobomok
• Zabulon Skipper, Poanes zabulon

References

• Kew gardens grass database
• The Observers Book of Grasses, Sedges and Rushes. Frances Rose. pages 38–39,42-47

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