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Elymus caput-medusae

Higher Taxonomy
Family: Poaceae (Gramineae)View DescriptionDichotomous Key

Habit: Annual to woody perennial herb; roots generally fibrous. Stem: generally round, hollow; nodes swollen, solid. Leaf: alternate, 2-ranked, generally linear, parallel-veined; sheath generally open; ligule membranous or hairy, at blade base. Inflorescence: various (of generally many spikelets). Spikelet: glumes generally 2; florets (lemma, palea, flower) 1--many; lemma generally membranous, sometimes glume-like; palea generally +- transparent, +- enclosed by lemma. Flower: generally bisexual, minute; perianth vestigial; stamens generally 3; stigmas generally 2, generally plumose. Fruit: grain, sometimes achene- or utricle-like.
Genera In Family: 650--900 genera; +- 10550 species: worldwide; greatest economic importance of any family (wheat, rice, maize, millet, sorghum, sugar cane, forage crops, ornamental, weeds; thatching, weaving, building materials). Note: Generally wind-pollinated. Achnatherum, Ampelodesmos, Hesperostipa, Nassella, Piptatherum, Piptochaetium, Ptilagrostis moved to Stipa; Elytrigia, Leymus, Pascopyrum, Pseudoroegneria, Taeniatherum to Elymus; Hierochloe to Anthoxanthum; Lolium, Vulpia to Festuca; Lycurus to Muhlenbergia; Monanthochloe to Distichlis; Pleuraphis to Hilaria; Rhynchelytrum to Melinis. The following taxa (in genera not included here), recorded in California from historical collections or reported in literature, are extirpated, lacking vouchers, or not considered naturalized: Acrachne racemosa (Roth) Ohwi, Allolepis texana (Vasey) Soderstr. & H.F. Decker, Amphibromus nervosus (Hook. f.) Baill., Axonopus affinis Chase, Axonopus fissifolius (Raddi) Kuhlm., Coix lacryma-jobi L., Cutandia memphitica (Spreng.) K. Richt., Dinebra retroflexa (Vahl) Panz., Eremochloa ciliaris (L.) Merr., Eustachys distichophylla (Lag.) Nees, Gaudinia fragilis (L.) P. Beauv., Miscanthus sinensis Andersson, Neyraudia arundinacea (L.) Henrard, Phyllostachys aurea Rivière & C. Rivière, Phyllostachys bambusoides Siebold & Zuccarini, Rottboellia cochinchinensis (Lour.) Clayton, Schedonnardus paniculatus (Nutt.) Branner & Coville, Schizachyrium cirratum (Hack.) Wooton & Standl., Schizachyrium scoparium (Michx.) Nash, Themeda quadrivalvis (L.) Kuntze, Thysanolaena latifolia (Hornem.) Honda, Tribolium obliterum (Hemsl.) Renvoize, Zea mays L., Zizania palustris L. var. interior (Fassett) Dore, Zoysia japonica Steud. Paspalum pubiflorum E. Fourn., Paspalum quadrifarium Lam., are now reported for southern California (J Bot Res Inst Texas 4:761--770). See Glossary p. 30 for illustrations of general family characteristics.
eFlora Treatment Author: James P. Smith, Jr., except as noted
Scientific Editor: James P. Smith, Jr., J. Travis Columbus, Dieter H. Wilken.
Elymus caput-medusae L.
Habit: Annual. Stem: decumbent to ascending, 2--7 dm, slender. Leaf: sheath glabrous, auricles 0.1--0.5 mm, rarely 0; ligule membranous, 0.2--0.6 mm, truncate; blade 1--3 mm, +- inrolled, glabrous to puberulent, long-ciliate near collar. Inflorescence: spike-like, dense, 1.5--6 cm (except awns), spikelets 2-ranked, 2(3--4) per node. Spikelet: glumes 2, equal, 5--80 mm, awl- to awn-like, erect to spreading or reflexed, stiff, fused at base, generally glabrous; axis breaking above glumes; florets (3), lower fertile, upper vestigial on prolonged axis; fertile lemma lanceolate 5--8 mm, 5-veined, awn (20)30--100+ mm, flat, straight to outwardly curved, palea = lemma; reduced florets with 3-veined lemmas, palea 0; anthers < 2 mm. Chromosomes: 2n=14.
Ecology: Disturbed areas; Elevation: < 2000 m. Bioregional Distribution: KR, NCoR, CaR, SNF, GV, SCoR, MP; Distribution Outside California: to British Columbia, Rocky Mountains, eastern United States (rare); native to Eurasia. Flowering Time: Apr--Jul
Synonyms: Taeniatherum caput-medusae (L.) Nevski; Taeniatherum asperum (Simonk.) Nevski
Jepson eFlora Author: James P. Smith, Jr.
Reference: Barkworth 2007 FNANM 24:283--287, 348--351, 353--369, 373--378
Index of California Plant Names (ICPN; linked via the Jepson Online Interchange)
Noxious Weed listed on the CDFA Weed Pest Ratings table
View the CDFA Pest Rating page for Elymus caput-medusae
Weed listed by Cal-IPC

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Citation for this treatment: James P. Smith, Jr. 2012, Elymus caput-medusae, in Jepson Flora Project (eds.) Jepson eFlora,, accessed on October 04, 2023.

Citation for the whole project: Jepson Flora Project (eds.) 2023, Jepson eFlora,, accessed on October 04, 2023.

Elymus caput-medusae
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© 2020 Neal Kramer
Elymus caput-medusae
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© 2004 Carol W. Witham
Elymus caput-medusae
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© 2011 Steve Matson
Elymus caput-medusae
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© 2021 Barry Rice
Elymus caput-medusae
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© 2016 Neal Kramer
Elymus caput-medusae
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© 2009 Barry Rice

More photos of Elymus caput-medusae in CalPhotos

Geographic subdivisions for Elymus caput-medusae:
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map of distribution 1
(Note: any qualifiers in the taxon distribution description, such as 'northern', 'southern', 'adjacent' etc., are not reflected in the map above, and in some cases indication of a taxon in a subdivision is based on a single collection or author-verified occurence).


Data provided by the participants of the  Consortium of California Herbaria.
View all CCH records
All markers link to CCH specimen records. The original determination is shown in the popup window.
Blue markers indicate specimens that map to one of the expected Jepson geographic subdivisions (see left map). Purple markers indicate specimens collected from a garden, greenhouse, or other non-wild location.
Yellow markers indicate records that may provide evidence for eFlora range revision or may have georeferencing or identification issues.

CCH collections by month

Duplicates counted once; synonyms included.
Species do not include records of infraspecific taxa, if there are more than 1 infraspecific taxon in CA.
Blue line denotes eFlora flowering time (fruiting time in some monocot genera).