CPC Plant Profile: Presidio Manzanita
Search / Plant Profile / Arctostaphylos hookeri var. ravenii
Plant Profile

Presidio Manzanita (Arctostaphylos hookeri var. ravenii)

The whitish-pink, urn-shaped flowers of Raven's manzanita appear in March and April. Photo Credit: Holly Forbes
Description
  • Global Rank: T1 - Critically Imperiled
  • Legal Status: Federally Endangered
  • Family: Ericaceae
  • State: CA
  • Nature Serve ID: 135046
  • Date Inducted in National Collection: 08/30/1988

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.

Participating Institutions
CPC's Plant Sponsorship Program provides long term stewardship of rare plants in our National Collection. We are so grateful for all our donors who have made the Plant Sponsorship Program so successful. We are in the process of acknowledging all our wonderful plant sponsorship donors on our website. This is a work in progress and will be updated regularly.
Updates
  • 08/18/2020
  • Genetic Research

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

  • 08/18/2020
  • Living Collection

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

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).

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.

MORE

Be the first to post an update!

Photos
Nomenclature
Taxon Arctostaphylos hookeri var. ravenii
Authority P.V. Wells
Family Ericaceae
CPC Number 222
ITIS
USDA
Common Names Presidio manzanita | Raven's manzanita
Associated Scientific Names Arctostaphylos hookeri var. ravenii | Arctostaphylos hookeri ssp. ravenii
Distribution Raven's manzanita is known only from the San Francisco Presidio. It was formerly found at several localities in San Francisco County.
State Rank
State State Rank
California S1
Habitat

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

Ecological Relationships

Raven's manzanita occurs on serpentine soil substrate (bedrock outcrop). The flowers are apparently self-compatible, producing seeds of less than 20% viability, although further study is needed.(USFWS 2001)

Pollinators
Common Name Name in Text Association Type Source InteractionID
Reintroduction
Lead Institution State Reintroduction Type Year of First Outplanting

Donate to CPC to Save this Species

CPC secures rare plants for future generations by coordinating on-the-ground conservation and training the next generation of plant conservation professionals. Donate today to help save rare plants from extinction.

Donate Today