Achnatherum is a genus of flowering plants in the grass family, Poaceae. It includes 20 species of needlegrass native to temperate Eurasia and North Africa. Several needlegrass species have been switched between Achnatherum and genus Stipa; taxonomy between the two closely related genera is still uncertain. In 2019 Peterson et al. reorganized the genera in tribe Stipeae based on molecular DNA studies, and placed the species from the Americas into other genera.
Description
The genus Achnatherum (syn. Lasiagrostis) is closely related to Stipa but can be distinguished by several morphological traits. Unlike Stipa, the young leaves of Achnatherum are convolute (rolled inward) rather than folded. Its spikelets are laterally compressed, and the lemma bears spreading hairs up to 4 mm long near the base. The awn is either straight or gently curved, but never abruptly bent (geniculate) or twisted below, which sets it apart from the characteristic awns of Stipa.
Taxonomy Original Description
The genus Achnatherum was first described by Palisot de Beauvois in 1812 in his Essai d'une Nouvelle Agrostographie. The protologue reads (translated):
Botanical history
The genus Achnatherum was first described by Palisot de Beauvois in Essai d'une Nouvelle Agrostographie (1812), where it was distinguished from allied genera such as Agrostis and Calamagrostis by its awned lemmas and distinctive palea morphology. In 1834, Bertoloni introduced the segregate genus Aristella in Flora Italica, describing species such as Aristella bromoides. Other authors also used names like Lasiagrostis Link (1827) for similar taxa. Modern taxonomic treatments, including Plants of the World Online and World Flora Online, regard Aristella and Lasiagrostis as heterotypic synonyms of Achnatherum.
During the 19th and 20th centuries, species now placed in Achnatherum were variously assigned to Stipa, Agrostis, and Arundo, reflecting uncertainty in the delimitation of tribe Stipeae. Recent molecular phylogenetic studies have clarified relationships within the tribe, supporting the recognition of Achnatherum as a distinct lineage and consolidating former segregate genera under this name.
Species 19 species are accepted by Plants of the World Online as of December 2025:
Unplaced species Achnatherum roshevitzii (unplaced) - Roshevich's achnatherum
Formerly placed here
Species previously included in Achnatherum:
Amelichloa brachychaeta (as Achnatherum brachychaetum ) - punagrass Amelichloa caudata (as Achnatherum caudatum ) - Chilean ricegrass Amelichloa clandestina (as Achnatherum clandestinum ) - Mexican ricegrass Barkworthia stillmanii (as Achnatherum stillmanii ) - Stillman's needlegrass Eriocoma arida (as Achnatherum aridum ) - Mormon needlegrass Eriocoma × bloomeri (as Achnatherum × bloomeri ) - Bloomer's ricegrass Eriocoma contracta (as Achnatherum contractum ) - contracted ricegrass Eriocoma coronata (as Achnatherum coronatum ) - crested needlegrass Eriocoma curvifolia (as Achnatherum curvifolium ) - Guadalupe ricegrass Eriocoma hymenoides (as Achnatherum hymenoides ) - Indian ricegrass Eriocoma hendersonii (as Achnatherum hendersonii ) - Henderson's needlegrass Eriocoma latiglumis (as Achnatherum latiglume ) - wide-glumed needlegrass Eriocoma lemmonii (Achnatherum lemmonii ) - Lemmon's needlegrass Eriocoma lettermanii (as Achnatherum lettermanii ) - Letterman's needlegrass Eriocoma lobata (as Achnatherum lobatum ) - lobed needlegrass Eriocoma nelsonii (as Achnatherum nelsonii ) - Nelson's needlegrass, Dore's needlegrass Eriocoma nevadensis (as Achnatherum nevadense ) - Nevada needlegrass Eriocoma occidentalis (as Achnatherum occidentale ) - western needlegrass Eriocoma parishii (as Achnatherum parishii ) - Parish's needlegrass Eriocoma perplexa (as Achnatherum perplexum ) - perplexing needlegrass Eriocoma pinetorum (as Achnatherum pinetorum ) - pinewoods needlegrass Eriocoma richardsonii (as Achnatherum richardsonii ) - Richardson's needlegrass Eriocoma robusta (as Achnatherum robustum ) - sleepygrass Eriocoma scribneri (as Achnatherum scribneri ) - Scribner needlegrass Eriocoma thurberiana (as Achnatherum thurberianum ) - Thurber's needlegrass Eriocoma swallenii (as Achnatherum swallenii ) - Swallen's needlegrass Eriocoma webberi (as Achnatherum webberi ) - Webber needlegrass Neotrinia splendens (Trin.) M.Nobis, P.D.Gudkova & A.Nowak (as Achnatherum splendens (Trin.) Nevsky) Pappostipa speciosa (as Achnatherum speciosum ) - desert needlegrass Pentameris pallida (as Achnatherum capense ) Ptilagrostis duthiei (as Achnatherum duthiei ) Pseudoeriocoma acuta (as Achnatherum acutum ) Pseudoeriocoma editorum (as Achnatherum editorum ) Pseudoeriocoma eminens (as Achnatherum eminens ) - southwestern needlegrass Stipellula parviflora (as Achnatherum parviflorum - Small-flowered needlegrass Thorneochloa diegoensis (as Achnatherum diegoense ) - San Diego needlegrass Timouria conferta (as Achnatherum caragana )
References
External links USDA Plants Profile for Achnatherum species Herbarium.usu.edu: Achnatherum Genus key