The Cedars Buckwheat (Eriogonum cedrorum) Potential Occurrence: Not Expected to Occur

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Magnoliopsida (Flowering Plants): Polygonaceae

The Cedars Buckwheat (Eriogonum cedrorum)

Potential Occurrence: Not Expected to Occur


Federal: None

State: None

CNPS: 1B.3

Photo: Roger Raiche and James Reveal

Photo: Roger Raiche
ther: None

Species Description: The Cedars Buckwheat is low and spreading, growing to be 10 to 50 cm across with loosely arranged rosettes of tufted leaves on slender, woody, branched stems growing from a stout taproot (Reveal and Raiche 2009).The leaves are broadly elliptic to ovate, thinly tomentose to glabrate or glabrous and greenish to light olive green with a 0.3 to 1.1 cm, densely tannish-white tomentose petiole (Reveal and Raiche 2009). The inflorescence is compound umbellate, slightly open with villous, grayish to greenish white branches and 4 to 6 bracts at the base (Reveal and Raiche 2009).The flowers are bright yellow becoming red to reddish maroon with an undertone of yellow and glabrous have obovate tepals (Reveal and Raiche 2009).The achenes are light yellowish brown and glabrous (Reveal and Raiche 2009).

Nomenclature: Eriogonum cedrorum Reveal & Raiche Polygonaceae (Reveal and Raiche 2009). This species was described in 2009 (CNPS 2010).

Synonyms: None

Distribution: This species is known from fewer than 5 occurrences in Sonoma County at The Cedars (CNPS 2010; Reveal and Raiche 2009)

Life History & Threats: The Cedars Buckwheat is a perennial herb flowering from June to September (CNPS 2010).

Habitat & Habitat Associations:

Vegetation Types: Habitat for this species is on serpentinite in coniferous forests in which the dominating trees are serotinous-coned conifers (CNPS 2010).

While The Cedars terrain is dominated by Sargent cypress woodland (Hesperocyparis sargentii (Jeps.) Bartel) and chaparral, the extremely steep canyon slopes are mostly open rock and talus forming extensive serpentine barrens. This open rock and talus is the only place that Eriogonum cedrorum grows…(From Reveal and Raiche 2009)

Elevation: 365 to 550 m (CNPS 2010) (The Study Area ranges from 230 to 710 m)

Geology and Soils: open serpentine rock and talus (Reveal and Raiche 2009) “Unless there is serpentine, and probably lots of it, it is extremely unlikely that … Eriogonum cedrorum…[is] present.” (Personal Communication, Raiche 2010).

Species Associations:

Typical associates are these: Asclepias solanoana Woodson, Aspidotis densa (Brack.) Lellinger, Cardamine californica (Nutt.) Greene var. sinuata (Greene) O.E. Schulz, Epilobium minutum Lindl. ex Lehm., Eriogonum luteolum Greene, E. nudum Douglas ex Benth. var. auriculatum (Benth.) J.P. Tracy ex Jeps., Hesperolinon spergulinum (A. Gray) Small, Minuartia douglasii (Fenzl ex Torr. & A. Gray) Mattf., Phacelia corymbosa Jeps., Sairocarpus vexillocalyculatus (Kellogg) D.A. Sutton, Streptanthus morrisonii, and S. barbiger Greene. Allium falcifolium Hook. & Arn., Eriophyllum lanatum (Pursh) Forbes, and Eschscholzia caespitosa Benth. are more restricted to certain sites.(From Reveal and Raiche 2009)

Conceptual Basis for GIS Model Development: Potential habitat in the Study Area was mapped as areas

  • above 335 and below 580 m elevation (A 30 m elevation buffer was added around known elevational occurrences of this species)

  • chaparral (i.e. Northern Mixed Chaparral and Scrub Oak).

  • steep slopes (> 30%) in the above habitat.

Closed cone conifers and serpentine soils are not known to occur in the Study Area.

Potential Occurrence on the Galbreath Wildlands Preserve:

Habitat: The Cedars Buckwheat occurs on serpentine rock and talus in chaparral and closed-cone coniferous forest. Potential habitat does not occur in the Preserve:

  • Serpentine soils, while common regionally, are not indicated by the GIS soil data as occurring in the Study Area. To verify the GIS information, we identified all areas (11 sites) of exposed rocky soils from high-resolution satellite imagery. During site visits to these areas, the only serpentine found were rocks exposed by road maintenance activity at a waterbar. Additionally, professional consolation with Roger Rachie (2010) confirmed that “Unless there is serpentine, and probably lots of it, it is extremely unlikely that … Eriogonum cedrorum…[is] present.”

  • Chaparral and closed-cone coniferous forest are not present on the Preserve.

Nearest Occurrence:

Documented Occurrences on Galbreath Wildlands Preserve: Previous species list for the Galbreath Wildlands Preserve did not document this species (SSU Field Station and Nature Preserves 2010).

Nearest Occurrence to Galbreath Wildlands Preserve: This species is known from 5 occurrences in Sonoma County with the total population count at 1500 to 2000 individuals (CNPS 2010; Reveal and Raiche 2009). The nearest occurrence is approximately 18 miles southeast of the Study Area at The Cedars (Reveal and Raiche 2009). An occurrence on the Galbreath Wildlands Preserve would be a northern range extension for this species.

Summary: The Cedars Buckwheat is “Not Expected to Occur” on the Preserve because habitat is not present and occurrence at the Preserve would be an 18 mile northeast range extension.


California Native Plant Society (CNPS). 2010. Inventory of Rare and Endangered Plants. Online edition, v7-10b. . Accessed 2010 Jul 13.

Reveal JL, Raiche R. 2009. Eriogonum cedrorum (Polygonaceae: Eriogonoideae), a new species from northwestern California. Journal of the Botanical Research Institute of Texas 3(2): 479-83.

Rachie R. 2010. Personal communication. 2010 Jul 12.

SSU Field Stations and Nature Preserves. 2010. Galbreath Wildlands Preserve Vascular Plant List. . Accessed 2010 Jun

Species Account Description: Linden Schneider

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