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Plant Profile

Presidio Manzanita (Arctostaphylos hookeri ssp. ravenii)

The whitish-pink, urn-shaped flowers of Raven's manzanita appear in March and April. Photo Credit: Holly Forbes

Global Rank: T1 - Critically Imperiled
Legal Status: Federally Endangered
Family: Ericaceae
State: CA
Nature Serve ID: 135046
Lifeform: Subshrub, Shrub
Date Inducted in National Collection: 08/30/1988

Description:

Raven's manzanita is a low-growing evergreen shrub with urn-shaped white to pink flowers. It was rediscovered by Peter Raven when he was a young boy in San Francisco in 1952 (it was described as subspecies ravenii in 1968). There is one naturally occurring plant left in its native habitat, located on a slope facing the Pacific Ocean in the San Francisco Presidio. This area is now managed by the Presidio Trust, a government corporation.

Where is Presidio Manzanita (Arctostaphylos hookeri ssp. ravenii) located in the wild?

Habitat:

This species grows best on slightly acidic, serpentine soils that occur in isolated outcrops.

Distribution:

Raven's manzanita is known only from the San Francisco Presidio. It was formerly found at several localities in San Francisco County.

States & Provinces:

Presidio Manzanita can be found in California

Which CPC Partners conserve Presidio Manzanita (Arctostaphylos hookeri ssp. ravenii)?

University of California Botanical Garden

Conservation Actions

08/18/2020

A study of the phylogeny of the Arctostaphylos hookeri complex (Markos et al. 1999).

08/18/2020

One known wild plant is maintained in an area on the Presidio Army Base in San Francisco, CA. Additional identical clones have been planted nearby and are also in cultivation at the University of California Botanical Garden at Berkeley and in other gardens (USFWS 2001).

Nature Serve Biotics

05/02/2017

Only one genetic individual exists in the wild; clones and seedlings have been artificially propagated from this individual and reintroduced. The original and reintroduced plants are located in remnant coastal scrub and grassland in the Presidio of San Francisco, California. It is threatened by failure to reproduce naturally, habitat loss, potential land use conflicts in limited restorable urban habitat, and disease (USFWS 2003).

Holly Forbes

01/01/2010

Low numbers Limited distribution Habitat loss due to urban development Competition with other species (shading) Fungal pathogen(s) (including twig blight)

Holly Forbes

01/01/2010

Holly Forbes

01/01/2010

A study of the phylogeny of the Arctostaphylos hookeri complex (Markos et al. 1999).

Holly Forbes

01/01/2010

On-going effort is needed to protect the original clone and additional plants from being shaded by invasive plants or damaged by vandalism. The number of populations should be increased at various locations within the Presidio to reduce the risk of extinction (USFWS 2001).

Holly Forbes

01/01/2010

Multiple experimental populations of sexually reproductive Raven's manzanita should be established at interior San Francisco locations isolated from the Presidio (USFWS 2001).

Holly Forbes

01/01/2010

The production of new seedling-grown plants resulting from self-fertilization under controlled conditions could be used in the development of new populations (USFWS 2001). Genetic analysis of open-pollinated seed generated plants at the UC Botanical Garden is needed to determine their status as pure strains or hybrids.