California Invasive Plant Council

Bromus diandrus

Synonyms: B. rigidus, B. rigidus var gussonei, B. gussonei

Common names: ripgut brome; great brome; ripgut grass

Bromus diandrus (ripgut brome) is an annual grass (family Poaceae) found throughout California and other western states. Ripgut brome is one of several European annual grasses that have displaced much of the native grass throughout California. Ripgut brome becomes very dry and flammable during the dry season, increasing wildfire frequency. Increased wildfire frequency leads to conversion of shrubland and woodland to grassland. Ripgut brome is reported to hybridize with two other invasive grasses: downy brome (Bromus tectorum) and red brome (Bromus madritensis). Brome seeds may spread great distances via water and soil movement and by clinging to animals and people.

Cal-IPC Rating: Moderate?

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: None?

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.

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

• The butterfly effect. Trumbo, Joel. Vol 20, Issue 2
• USFWS and PG&E partner to protect species. Terrazas, Louis. Vol 20, Issue 1
• “Conservation Across Borders” in San Jose. Cal-IPC. Vol 14, Issue 2
• Exploring alternative methods for vegetation control and maintenance along roadsides. Young, Steve L.. Vol 10, Issue 4
• The use of fire for yellow starthistle (Centaurea solstitialis) management and restoration of native grasslands at Sugarloaf Ridge State Park. Hastings, Marla; DiTomaso, Joe. Vol 04, Issue 1
• Portrait of an invader II: The ecology and management of Carpobrotus edulis. Albert, Marc E.. Vol 03, Issue 2
• Control of exotic plants in an herbaceous understory. Perala, Christine; Hoover, Doris A.; Parra-Szijj, E.A.. Vol 01, Issue 3

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.

• Aridity constrains the adaptive potential of plant invaders under nitrogen deposition. Valliere, Justin (2023)
• The role of fire in managing invasive species at the Santa Rose Plateau Ecological Reserve. Laskey, Hailey; Principe, Zach (2022)
• Using selective herbicides to control invasive annual grasses. Echols, Aaron (2022)
• Interactions among insects and weeds in western U.S. forests. Fettig, Christopher; Runyon, Justin; Trilling, Jared; Mortenson, Leif; Audley, Jackson (2020)
• Integrating weed control and trait-screened seed mixes to reduce the risk of postfire type conversion from coastal sage scrub to annual grasslands. Teller, Noah (2019)

Other Bromus diandrus Information

• CalPhotos - Images of plants taken mostly in California.
• Calflora - Distribution map and records of this species in California.
• CalWeedMapper - Distribution map of this species in California with ability to determine regional priorities.
• 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