Poa annua L. Sp. Pl. 1: 68 1753.

Soreng, Robert J., Sylvester, Steven P., Sylvester, Mitsy D. P. V. & Clark, Vincent Ralph, 2020, New records and key to Poa (Pooideae, Poaceae) from the Flora of Southern Africa region and notes on taxa including a diclinous breeding system in Poa binata, PhytoKeys 165, pp. 27-50 : 27

Poa annua L. Sp. Pl. 1: 68 1753.

Ochlopoa annua (L.) H. Scholz, Ber. Inst. Lanschafts-Pflanzenokologie Univ. Hohenheim Beih. 16: 58. 2003.

Type.

Habitat in Europa ad vias. (lectotype, designated by Soreng 2020: 254: LINN (LINN-87.17!, right-hand plant)).

Many heterotypic synonyms.

- P. sect. Micrantherae Stapf, Fl. Brit. India 7(22): 343. 1897 [1896]. Type, P. annua L.

Distribution.

widespread in Lesotho and South Africa. Introduced, native to Eurasia and North Africa, now worldwide.

Ecology.

weedy in temperate climates.

Flowering.

anytime.

Economics.

common, a pesky garden, lawn and trail weed of little consequence.

Vouchers.

Lesotho. Menoaneng Pass, on road between Rafolatsane and Thaba-Tseka, S29.427251 E28.947895, 3086 m alt., basaltic substrate, Afro-alpine grassland, 24 Feb 2020, S.P. Sylvester et al. 3609 (PRE, US); Sani Pass area, close to Sani river northwest of Sani Mountain Lodge, S29.562993 E29.246806, 2803 m alt., basaltic substrate, short Afro-alpine grassland, close to a pool of water, frequently to heavily grazed, 26 Feb 2020, S.P. Sylvester et al. 3625 (NU, PRE, US). South Africa. Eastern Cape: Naudes Nek pass, near Rhodes, in grassland next to radio tower, S30.764488 E28.090455, 2607 m alt., basaltic substrate, overgrazed alpine grassland with some low Erica and Helichrysum shrubs, gently sloping, moderately deep soil, 13 Feb 2020, S.P. Sylvester et al. 3503 (NU, PRE, US); Eastern Cape: Tiffindell Ski Area, S30.675222 E27.959111, 2529 m alt., basaltic substrate, heavily-grazed livestock paddocks amongst alpine grassland, 12 Feb 2020, S.P. Sylvester et al. 3472 (NU, PRE, US); Eastern Cape: Tiffindell Ski Area, S30.675667 E27.958950, 2532 m alt., basaltic substrate, grazed alpine grassland next to livestock paddocks, 12 Feb 2020, S.P. Sylvester et al. 3477 (NU, PRE, US).

Notes.

Poa annua is a tetraploid species derived from hybridisation, somewhere around the Mediterranean Sea, between two diploids that overlap in that region: P. infirma (maternal parent, contributor of the plastid genotype) and P. supina Schrad. (paternal parent, providing the nuclear ribosomal internal [and also external] transcribed spacer genotypes) ( Soreng et al. 2010). It is sometimes considered the world’s most widespread weed. Poa annua grades in form in the directions of both parents, sometimes making it tricky to differentiate, especially from P. infirma . Hybrids with P. supina , called P. x nannfeldtii (H. Scholz ex Val.N.Tikhom.) Nosov, exhibit a C-value indicative of triploidy (Soreng, pers. obs.). Self-compatible, mostly inbreeding, it is gynomonoecious. The upper florets within spikelets being pistillate facilitates outcrossing. 2 n = 28. - Mimu genotype.