Aira is a genus of annual grasses in the family Poaceae (order Poales), native to the Old World — primarily western and southern Europe, central and southwest Asia, and Africa. The genus belongs to the broader grass tribe and is closely related to Deschampsia and Koeleria, with which it shares the common name hair-grass, a reference to the characteristically slender, hair-like leaves and stems.
Plants in the genus are typically small and delicate, reaching 20–40 cm in height. They are found on dry, sandy, often nutrient-poor soils, and their fine-textured foliage and feathery, branched panicles give them an airy, gossamer appearance in flower and seed. This quality makes several species valued as ornamental plants, particularly in dried flower arrangements where the light seed heads persist well.
The circumscription of Aira has changed considerably over time. Many species historically placed here have been transferred to other grass genera, including Deschampsia, Koeleria, Agrostis, Poa, Corynephorus, Eragrostis, and others, substantially reducing the number of species now accepted within the genus. Two species are currently recognised in the GBIF backbone: Aira cupaniana and Aira praecox.
Etymology
The common name hair-grass refers to the very slender, hair-like leaves and stems characteristic of the genus, a trait shared with the related genera Deschampsia and Koeleria. The genus name Aira derives from ancient Greek, used historically for a darnel or tare grass.
Distribution
Aira is native to western and southern Europe, central and southwest Asia, and Africa. Species favour dry, sandy, often open habitats across this range.
Ecology
Species of Aira are characteristically plants of dry, sandy, nutrient-poor sites — heathlands, sand dunes, thin acidic soils, and open disturbed ground. Their small stature and rapid life cycle (most are annuals) suit them to habitats with low competition.
Taxonomy Notes
The genus has undergone significant revision; a large number of species formerly placed in Aira have been transferred to other genera such as Deschampsia, Koeleria, Agrostis, Corynephorus, Poa, Eragrostis, Sporobolus, and many others. Only a small core of species is now retained in Aira sensu stricto.
