California Invasive Plant Council

Elymus caput-medusae

Synonyms: Taeniatherum caput-medusae

Common names: medusahead

Elymus caput-medusae (medusahead) is a winter annual (family Poaceae) that typically invades disturbed sites, grasslands, openings in chaparral and oak woodlands. Medusahead out-competes native grasses and forbs and is found throughout northwestern California. After they set seed, medusahead plants persist as a dense litter layer that prevents germination and survival of native species, ties up nutrients, and contributes to fire danger in the summer.

Cal-IPC Rating: High?

Explanation of Cal-IPC ratings

• High – These species have severe ecological impacts on physical processes, plant and animal communities, and vegetation structure. Their reproductive biology and other attributes are conducive to moderate to high rates of dispersal and establishment. Most are widely distributed ecologically.
• Moderate – These species have substantial and apparent-but generally not severe-ecological impacts on physical processes, plant and animal communities, and vegetation structure. Their reproductive biology and other attributes are conducive to moderate to high rates of dispersal, though establishment is generally dependent upon ecological disturbance. Ecological amplitude and distribution may range from limited to widespread.
• Limited – These species are invasive but their ecological impacts are minor on a statewide level or there was not enough information to justify a higher score. Their reproductive biology and other attributes result in low to moderate rates of invasiveness. Ecological amplitude and distribution are generally limited, but these species may be locally persistent and problematic.
• Alert – An Alert is listed on species with High or Moderate impacts that have limited distribution in California, but may have the potential to spread much further.
• Watch – These species have been assessed as posing a high risk of becoming invasive in the future in California.

CDFA Rating: -*?

Explanation of CDFA ratings

• A – A pest of known economic or environmental detriment and is either not known to be established in California or it is present in a limited distribution that allows for the possibility of eradication or successful containment.
• B – A pest of known economic or environmental detriment and, if present in California, it is of limited distribution.
• C – A pest of known economic or environmental detriment and, if present in California, it is usually widespread.
• D – An organism known to be of little or no economic or environmental detriment, to have an extremely low likelihood of weediness, or is known to be a parasite or predator.
• Q – An organism or disorder suspected to be of economic or environmental detriment, but whose status is uncertain because of incomplete identification or inadequate information.
• * – An asterisk next to the rating indicates that a plant is included in the CCR Section 4500 list of California State Noxious Weeds.
• -* – This plant is included in the CCR Section 4500 list of California State Noxious Weeds, but is otherwise not rated.

More details

Assessment(s)

Plant Assessment Form - Information gathered by Cal-IPC on the impacts, rate of spread, and distribution of invasive plants in California. Does not include management information.

Species ID Card

Invasive Species ID Card - To support field identification of early detection species, Cal-IPC has designed a set of Species ID cards that can be downloaded, printed double-sided, and trimmed to size.

Special Reports

Weed Management Notes

• Management Notes - Information on management techniques and effectiveness from the University of California Cooperative Extension’s Weed Research & Information Center.

Cal-IPC Newsletter Articles

• Weed worker legend Joe DiTomaso retires. Brusati, Elizabeth. Vol 25, Issue 2
• One Tam unites around Marin’s mountain. Kesel, Rachel. Vol 24, Issue 3
• Native soil bacteria as biocontrol. Bean, Travis; Gornish, Elise. Vol 24, Issue 2
• Wildland Weed News. Cal-IPC. Vol 22, Issue 3
• Prescribed grazing for invasive plant control on rangelands. Davy, Josh; Tate, Kenneth; Roche, Leslie. Vol 21, Issue 3
• Impacts of native vs. exotic grassland vegetation. Eviner, Valerie; Heraty, Joanne; Baty, Jill; Malmstrom, Carolyn; Rice, Kevin. Vol 21, Issue 3
• Partnering with college helps track medusahead. Alford, Jim; Benedetti, Daniel; Jennings, Nathan. Vol 20, Issue 3
• Jepson Manual 2nd ed. invasive plant name changes. Brusati, Elizabeth. Vol 20, Issue 2
• Exploring alternative methods for vegetation control and maintenance along roadsides. Young, Steve L.. Vol 10, Issue 4

Cal-IPC Symposium Presentations

Presentations are linked where available. Where a presentation is not available, find more information by reading the abstract in the Cal-IPC Symposia Archive.

• Biological control of invasive annual grasses. Rector, Brian (2023)
• Prescription fire for medusahead (Elymus caput-medusae) control and impacts to species composition in an invaded California grassland. Mills, Jason (2023)
• Expanding the use of prescribed fire as an ecosystem stewardship tool in fire-adapted landscapes. Lopez, Hannah (2022)
• Update on recent biological control releases against invasive plants by the USDA-ARS. Moran, Patrick; Pratt, Paul; Smith, Lincoln (2022)
• Winter annual grass control: experiences with Indaziflam in NE California. Getts, Tom (2022)
• Understanding herbicide labels and drones better. Miller, Beau (2021)
• Utilizing pathways of invader dominance to identify natives of concern. LaForgia, Marina (2021)
• Can tree and vine herbicide be effective for medusahead? Getts, Tom (2020)
• Evaluating control of late-season noxious grassland invasives with multiple approaches: wildfire, prescribed fire, native grass restoration, and organic herbicides. Eviner, Valerie (2020)
• Mapping weeds and rare plants to inform management and conservation in the Zaca and Jesusita fires. Calloway, Stephanie; Schneider, Heather; Knapp, Denise (2018)
• Recent research on invasive weeds at the European Biological Control Laboratory (EBCL). Smith, Lincoln; Bon, Marie-Claude; Desurmont, Gaylord; Kashefi, Javid; Sforza, René; Tannières, Mélanie; Cristofaro, Massimo; Marini, Francesca; Goolsby, John; Rector, Brian; Vidovic, Biljana; Winkler, Daniel; Moran, Patrick (2018)
• Revegetating medusahead (Taeniatherum caput medusae)-invaded rangeland. Nafus, Aleta; Davies, Kirk (2018)
• Grassland restoration and invasive weed management in Southern California: Medusahead as a case study. McDonald, Chris (2017)
• Plant community responses to cattle grazing in a noxious weed-dominated rangeland. Roche, Leslie; Tate, Ken (2016)

Other Elymus caput-medusae Information

• Bugwood - National database from the Center for Invasive Species and Ecosystem Health at the University of Georgia.
• CalPhotos - Images of plants taken mostly in California.
• Calflora - Distribution map and records of this species in California.
• EDDMapS - Distribution of this species in North America.
• Jepson Interchange - Information on this plant's taxonomy, biology, and distribution from UC Berkeley's Jepson Herbarium.
• USDA PLANTS Database - Information on identification and distribution, with links to websites in individual states.

Additional photos