(Torr.) J.D.Freeman 
Trillium angustipetalum, with the common name is narrowpetal wakerobin, is a species of Trillium, plants which may be included within the Liliaceae (lily family) or the newer family Melanthiaceae. 
The plant is native to northern and central California and southwestern Oregon, where it occurs in forests, woodlands, chaparral, and riparian zones.  It is found in the Klamath Mountains, western Sierra Nevada foothills, and Outer Southern California Coast Ranges. 
Trillium angustipetalum is a rhizomatous perennial herb with one or more erect stems growing up to 70 centimetres (28 in) in height. There is a whorl of three large leaves generally described as bracts each measuring up to 25 centimetres (9.8 in) in length and round or somewhat oval. They are green and mottled with brownish or darker green spots.
Each stem produces one flower, which is held on top of the bracts. The ill-scented flower has three lance-shaped green or red sepals and three narrow purple or maroon petals measuring up to 11 centimetres (4.3 in) long.
- Calflora: Trillium angustipetalum
- Kew World Checklist of Selected Plant Families
- "Trillium angustipetalum". Natural Resources Conservation Service PLANTS Database. USDA. Retrieved 15 December 2015.
- Biota of North America Program 2013 county distribution map
- Calflora taxon report, University of California, Trillium angustipetalum (Torrey) Freeman narrow petaled wakerobin, narrowpetal wakerobin
- Flora of North America, Trillium angustipetalum
|Wikispecies has information related to: Trillium angustipetalum|
- Calflora Database: Trillium angustipetalum (Narrowpetal wakerobin, Narrow petaled Wakerobin)
- Jepson Manual eFlora (TJM2) treatment of Trillium angustipetalum
- Biodiversity Information Serving Our Nation (BISON): occurrence data + maps for Trillium angustipetalum
- Trillium angustipetalum in the CalPhotos Photo Database, University of California, Berkeley
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