Achnatherum


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 is closely related to Stipa but can be distinguished by several morphological traits. Unlike Stipa, the young leaves of Achnatherum are convolute 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 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 :

Botanical history

The genus Achnatherum was first described by Palisot de Beauvois in Essai d'une Nouvelle Agrostographie, 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 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 - Roshevich's achnatherum

    Formerly placed here

Species previously included in Achnatherum:
  • Amelichloa brachychaeta - punagrass
  • Amelichloa caudata - Chilean ricegrass
  • Amelichloa clandestina - Mexican ricegrass
  • Barkworthia stillmanii - Stillman's needlegrass
  • Eriocoma arida - Mormon needlegrass
  • Eriocoma × bloomeri - Bloomer's ricegrass
  • Eriocoma contracta - contracted ricegrass
  • Eriocoma coronata - crested needlegrass
  • Eriocoma curvifolia - Guadalupe ricegrass
  • Eriocoma hymenoides - Indian ricegrass
  • Eriocoma hendersonii - Henderson's needlegrass
  • Eriocoma latiglumis - wide-glumed needlegrass
  • Eriocoma lemmonii - Lemmon's needlegrass
  • Eriocoma lettermanii - Letterman's needlegrass
  • Eriocoma lobata - lobed needlegrass
  • Eriocoma nelsonii - Nelson's needlegrass, Dore's needlegrass
  • Eriocoma nevadensis - Nevada needlegrass
  • Eriocoma occidentalis - western needlegrass
  • Eriocoma parishii - Parish's needlegrass
  • Eriocoma perplexa - perplexing needlegrass
  • Eriocoma pinetorum - pinewoods needlegrass
  • Eriocoma richardsonii - Richardson's needlegrass
  • Eriocoma robusta - sleepygrass
  • Eriocoma scribneri - Scribner needlegrass
  • Eriocoma thurberiana - Thurber's needlegrass
  • Eriocoma swallenii - Swallen's needlegrass
  • Eriocoma webberi - Webber needlegrass
  • Neotrinia splendens M.Nobis, P.D.Gudkova & A.Nowak
  • Pappostipa speciosa - desert needlegrass
  • Pentameris pallida
  • Ptilagrostis duthiei
  • Pseudoeriocoma acuta
  • Pseudoeriocoma editorum
  • Pseudoeriocoma eminens - southwestern needlegrass
  • Stipellula parviflora - San Diego needlegrass
  • ''Timouria conferta''