Overview

Brief Summary

Species Abstract

Ceanothus divergens is an erect mound-type shrub maturing at a height of one half to 1.5 meters. Its occurrence is restricted to a limited portion of the North Coast Ranges within only Sonoma and Napa County, California, particularly the Sonoma Mountains and the Mayacamas Mountains at elevations ranging from 150 to 950 meters. Occurrences are chiefly on volcanic slopes in chaparral or open canopy areas of mixed oak woodlands.

The reddish brown plant stems are ascending to generally erect; opposite leaves are five to twelve millimeters in length, normally exceeding the width by a factor of two. There are three to eleven spiny teeth per leaf. The blue to purple flowers are exhibited in mid-February to mid-April. This species is classified as rare and of limited distribution by the California Native Plant Society, who has conducted original species field surveys for the Annadel State Park populations as recently as March, 2012; chief threats are population loss by stochasticity and aggressive brush clearing by Pacific Gas and Electric in power line corridors.

The entire genus is situated in a monphyletic clade or sub-family known as the Arbutoideae, which is populated by taxa having bright fleshy berries with fibrous or bony endocarp.. Evolution of the genus is relatively recent, with hybridization playing an important role; however, convergent evolution patterns appear to complicate cladistic constructions for certain portions of the genus cladogram. In any case, fossil ancestors of the Arctostaphylos genus have been suggested to have occurred in the Middle Miocene, with modern species beginning to take shape in the Late Tertiary.

  • Julie Evens, C.Michael Hogan et al. 2012. California Natural Diversity Data Base: Ceanothus divergens. Species reports for Annadel State Park. CNDDB
  • C.Michael Hogan. 2012. Arctostaphylos. Encyclopedia of Earth. Eds. M. McGinley & C.Cleveland. National council for Science and the Environment. Washington DC http://www.eoearth.org/article/Arctostaphylos
  • Jepson Manual. 1993. Ceanothus divergens
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Distribution

Global Range: California endemic, Lake, Napa, and Sonoma Counties.

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Ecology

Habitat

Comments: Chaparral; serpentinite or volcanic, rocky.

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Conservation

Conservation Status

National NatureServe Conservation Status

United States

Rounded National Status Rank: N2 - Imperiled

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NatureServe Conservation Status

Rounded Global Status Rank: G2 - Imperiled

Reasons: This Californian endemic taxon is treated by some as Ceanothus divergens, and by others as Ceanothus purpureus ssp. divergens. It occurs in Lake, Napa and Sonoma Counties. It is threatened by development in one area.

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Threats

Comments: Development is a threat (CNPS 2001).

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Wikipedia

Ceanothus divergens

Ceanothus divergens, commonly known as Calistoga ceanothus, is an evergreen shrub in the Rhamnaceae family, an endemic of California.

Contents

Description

This plant has a growth habit described as ascending to erect and may attain height. The plant's preferred habitat is on shrub-covered, rocky, volcanic slopes. The hermaphrodite blue or purple flowers bloom in April and May.[1]

The sub-globose fruits are five to six millimeters in diameter.[2]

Distribution

Occurrence is primarily in the Northern California Coast Ranges, such as near Calistoga, at altitudes of less than 500 meters.[3]

See also

References

  1. ^ Plant profile for Ceanothus divergens: Plants for a future
  2. ^ C. C. Parry, Ceanothus divergens, Proc. Davenport A,cad. Nat. Sci. 5: 173. 1889
  3. ^ Jepson Manual. University of California Press (1993)
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