California Invasive Plant Council

Iris pseudacorus

Synonyms: Iris acoriformis, Iris bastardi, Iris curtopetala, Iris lutea, Iris paludosa

Common names: yellowflag Iris; pale yellow Iris

Iris pseudacorus (yellowflag Iris) (family Iridaceae) invades wetlands and meadows along coastal California and some inland counties. Iris pseudacorus is a fast-growing and rapidly-spreading invasive plant that can out-compete other wetland plants, forming almost impenetrable thickets, in much the same way as cattails do.

Cal-IPC Rating: Limited?

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: B?

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)

Iris pseudacorus 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.

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

• PlantRight update: Nursery survey and plant list. Falzone, Stephanie. Vol 25, Issue 3
• Wildland Weed News. Cal-IPC. Vol 22, Issue 2
• Don’t sell a pest: A new partnership to prevent plant invasions through horticulture. Connick, Sarah; Gerel, Mike. Vol 13, Issue 2
• Roundup of Arundo projects reveals commitment, strategic weakness. Kelly, Mike. Vol 07, Issue 2

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.

• Biology and ecology of yellow flag iris: Research updates to support integrated weed management. Grewell, Brenda (2023)
• Iris pseudacorus germination resilience to high salinity exposure supports risk of invasive spread in tidal wetlands. Gillard, Morgane; Castillo, Jesus; Mesgaran, Mohsen; Futrell, Caryn; Grewell, Brenda (2020)
• Exploring the germination ecology of Iris pseudacorus populations invading California wetlands. Gillard, Morgane B.; Castillo, Jesús M.; Mesgaran, Mohsen; Futrell, Caryn J.; Grewell, Brenda J. (2019)
• High salinity exposure does not preclude germination of invasive Iris pseudacorus from populations along a Delta-San Francisco Estuary salinity gradient. Gillard, Morgane (2019)
• Partnering to prevent invasions of plants of horticultural origin. Connick, Sarah; Gerel, Mike (2004)

Other Iris pseudacorus 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.
• 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