PlantaeDB Logo
Login Sign-up

Genus Aira in Family Poaceae

In botanical taxonomy, a genus (plural genera) is a rank used to group closely related species within a family. In the hierarchy, genus sits below family and above species.

Genera are defined by shared morphological, anatomical, and genetic characteristics (for example, features of flowers, fruits, seeds, or leaves) that indicate a close evolutionary relationship among the species they contain.

Each genus can include one or more species. Examples include Rosa (roses) and Solanum (nightshades, including tomato and eggplant).

Do you wish to read more about plant taxonomy? Click here!

Genus Description

Suggest a correction!

Aira, a genus of annual grasses in Poaceae (subfamily Pooideae, tribe Poeae), comprises about 10 species that range across Europe and North Africa, with introductions in other temperate regions; the name Aira has nomenclatural priority over several reinstated names, and the genus remains compact around small, tufted annuals. Plants are diminutive, with slender culms and narrow, inrolled leaf blades; sheaths are closed, ligules are membranous, and glumes are thin and acute. Spikelets are small, two-flowered, and shed the florets entire at maturity; lemmas are typically unawned or bear a very short apical bristle, and the caryopsis has a linear hilum.

Centers of diversity lie in Mediterranean-type and temperate Europe, with several species restricted to coastal or open habitats; Aira praecox occurs on sand dunes and heaths, while A. caryophyllea occupies disturbed ground, and the narrow endemic A. tenorei occurs in Sardinia and Corsica. Several taxa are adapted to dry, nutrient-poor sites and establish after disturbance, reflecting a life-history strategy of rapid completion from seed to seed.

Pollination is by wind, and fruit is an easily dispersed caryopsis; base chromosome number has been reported as x=7 for the genus. Phylogenetic work in tribe Poeae consistently places Aira within the airinoid grade near Corynephorus and distinct from Deschampsia, which retains broader perennials; Avenella flexuosa, previously placed in Aira, is now accepted as a separate lineage, and Deschampioa has been reinstated to accommodate former Aira sect. Deschampioa species (Cope & Stace, 1978; GRASSBASE, 2024). No subgeneric arrangement is widely applied.

Species of Aira are widely cultivated as ornamental “hair grasses” in rockeries and meadow plantings, valued for their fine texture and silvery inflorescences; none are significant crops or timbers. Some taxa are naturalized weeds in non-native ranges, but their environmental impacts are generally minor.

Conservation varies by species; localized endemics such as Aira tenorei face habitat loss, whereas widespread taxa are secure. Continued taxonomic clarity and targeted assessments for narrow endemics remain priorities (POWO, 2024; WFO, 2024; Saarela et al., 2015).

Pick a Species to see its components: