Lachnagrostis is a genus of grasses in the family Poaceae (order Poales), comprising approximately 38 accepted species distributed across temperate regions of the Southern Hemisphere and beyond. The genus ranges across Australia, New Zealand, Pacific Islands, southern and eastern Africa, and parts of South America. It is placed in the large tribe Agrostideae, and species are frequently treated as members of the closely related genus Agrostis, reflecting the blurred boundaries between these two groups.
Plants are tufted perennials or annuals. The inflorescence is a characteristically open, much-branched panicle that often detaches completely at maturity — a feature that aids in wind dispersal. Spikelets are small and mostly one-flowered, with the rachilla extending beyond the floret. Glumes are roughly equal in length, firmer than the lemma, acute, and single-nerved, with a scabrid keel. The lemma is shorter and thinner than the glumes, typically hairy (though sometimes glabrous), with three to five nerves and a dorsal awn that is scabrid and may be straight or geniculate; the palea is 50 to 100% the length of the lemma. The genus name derives from the Greek lachnos, meaning "wool," alluding to the hairy lemmas characteristic of most species.
Australia is the primary centre of diversity with approximately 21 species, occurring across all states except the Northern Territory. New Zealand hosts 12 species, 10 of which are endemic, and the genus also occurs in South Africa, Lesotho, Eswatini, eastern Africa from Eritrea to the Cape, Yemen, and in Ecuador and Peru. Lachnagrostis filiformis is the most widespread species, extending through Australia, New Zealand, New Guinea, the Lesser Sunda Islands, and Easter Island, with naturalized populations in South Africa, Taiwan, and scattered localities in the Americas.
Etymology
The genus name Lachnagrostis is derived from the Greek lachnos, meaning "wool," combined with Agrostis (a related genus of bent grasses). The name alludes to the hairy lemmas found in most species — effectively meaning "hairy Agrostis."
Distribution
Lachnagrostis is centered in Australasia: Australia holds approximately 21 species (present in all states except the Northern Territory) and New Zealand 12 species, of which 10 are endemic. The genus extends to South Africa, Lesotho, Eswatini, eastern Africa (Eritrea south to the Cape Province), Yemen, Ecuador, and Peru. Lachnagrostis filiformis has additionally naturalized in South Africa, Taiwan, and scattered locations in the Americas.
Taxonomy Notes
Species of Lachnagrostis are frequently treated as members of Agrostis (bent grasses), and the boundary between the two genera is not universally agreed upon. GBIF places the genus in the family Poaceae, order Poales. The genus was established by the botanist Trinius (abbreviated "Trin.") and contains roughly 38 accepted species under the broader circumscription, versus approximately 20 under the narrower circumscription applied in the NSW flora.
