Taxon Report

Micropus amphibolus Gray

Mt. Diablo cottonweed

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Taxon Summary

Micropus amphibolus, commonly known as Mt. Diablo cottonweed, is a annual herb in the Asteraceae that is found only in California. It occurs within Broadleafed upland forest, Chaparral, Cismontane woodland, and Valley and foothill grassland, growing at elevations from 45 to 825 meters. Micropus amphibolus is ranked 3.2, Plants About Which We Need More Information, A Review List; Moderately threatened in California.

Classification


Scientific Name:	Micropus amphibolus Gray
Common Name:	Mt. Diablo cottonweed
Family:	Asteraceae
Element Code:	PDAST6D030
USDA Plants Symbol:	MIAM3
Synonyms/Other Names:	Stylocline amphibola (Gray) J.T. Howell

Ecology and Life History


Lifeform:	annual herb
Blooming Period: Mar-May	Mar-May
Elevation:	45-825 (150-2705)
General Habitats:	Broadleafed upland forest, Chaparral, Cismontane woodland, Valley and foothill grassland
Microhabitat:	Rocky
Microhabitat Details:

Conservation Status


CA Rare Plant Rank:	3.2
Global Rank:	G3G4
State Rank:	S3S4
State List:	None
Fed List:	None
Other Status:	SB_UCSC
CRPR Changes:

Occurrence Data from the CNDDB


Total Occurrences:	0
Element Occurrence Ranks:
Excellent (A)	0
Good (B)	0
Fair (C)	0
Poor (D)	0
None (X)	0
Unknown (U)	0

Location


California Endemic: True
California Counties and Islands: Name (Code)
Lake (LAK), Marin (MRN), Monterey (MNT), Napa (NAP), San Joaquin (SJQ), Santa Cruz (SCR), Sonoma (SON)
Quads: Name (Quad Code)
Ano Nuevo (3712213), Cedar Mtn. (3712155), Davenport (3712212), Felton (3712211), Glen Ellen (3812235), Kelseyville (3812287), Laurel (3712118), Petaluma River (3812225), San Francisco North (3712274), Spreckels (3612156), Yountville (3812243)

Threat List Data from the CNDDB


Threat List Total:	0
EOs with Threat Listed:	Total EOs	% of EOs
	0	0 %

Notes



Move to List 4? Can be confused with M. californicus. Many occurrences old; need current status information. Potentially threatened by vineyard development. See Proceedings of the American Academy of Arts and Sciences 17:214 (1882) for original description.
Threats:

Taxonomy:

Selected References

Citation California Native Plant Society, Rare Plant Program. 2025. Rare Plant Inventory (online edition, v9.5.1). Website https://www.rareplants.cnps.org [accessed 1 November 2025].