California Invasive Plant Council

Hieracium aurantiacum

Synonyms: Pilosella aurantiacum

Common names: orange hawkweed

Hieracium aurantiacum (Orange hawkweed) is an herbaceous perennial forb that reproduces by seed, rhizomes, and stolons. It is native to northern and central Europe and is common along roadsides, meadows and in forest understories. Once established, Hieracium aurantiacum can spread quickly, excluding native species. It was introduced in 1875 to the US in Vermont as a garden ornamental, was marketed for its attractive orange flowers for a long period, and has since repeatedly escaped cultivation. This plant is listed as a noxious weed in the western US in Colorado, Idaho, Oregon, Montana, and Washington.

Cal-IPC Rating: Watch

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)

Plant Risk Assessment - An evaluation of the potential for a plant to be invasive in California.

Weed Management Notes

Cal-IPC Newsletter Articles

• Impressions from north of the border: Oregon's 2022 Interagency Noxious Weed Symposium. Burger, Jutta. Vol 31, Issue 1
• Inventory Update 2022. Burger, Jutta. Vol 30, Issue 1
• Hawai’i: Ground zero for plant invasions - and EMAPi13!. Darin, Gina. Vol 23, 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.

• 2019 Weed Alerts. Burger, Jutta; Price, Bob (2019)

Other Hieracium aurantiacum 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.
• GBIF - Global distribution information.
• 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.
• The Plant List - Global taxonomic resource and collaborative clearinghouse from Kew Gardens, the Royal Botanic Gardens, the Missouri Botanic Garden and others.

Additional photos