About Poa annua
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. Though P. annua is commonly considered a solely annual plant 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. This grass may have originated as a hybrid between Poa supina and Poa infirma. 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 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 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.
Example of grass pollencountings on daylevel
Example of SEM-image of grasspollen
SEM grass pollen, copyrighs J.Derksen