CPC Plant Profile: Hoffmann's Rockcress
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Plant Profile

Hoffmann's Rockcress (Boechera hoffmannii)

Vegetative plants less than 3 years old have solitary leaf rosettes about 1-3 cm wide and less than 5 cm tall. Photo Credit: Dieter Wilken
Description
  • Global Rank: G1 - Critically Imperiled
  • Legal Status: Federally Endangered
  • Family: Brassicaceae
  • State: CA
  • Nature Serve ID: 131731
  • Date Inducted in National Collection: 09/18/2021

Less than 150 plants in 3 populations are known to exist. Two populations each have less than 5 reproductive plants annually. The remaining population may have as many as 30 reproductive individuals in any one year. Although reproductive plants produce many fruits and seeds, most of the seeds are dispersed to adjacent, unfavorable sites. The primary threats to survival and recovery are feral pig activity, subsequent erosion, and competition from alien grasses. Plants are monocarpic, growing vegetatively for 3-5 years before flowering, fruiting and dying (Wilken 1996). Reproductive plants grow up to 70 cm tall, each with about 40 fruits that contain about 125 seeds. The minute seeds are slightly winged and dispersed by wind. Vegetative plants less than 3 years old have solitary leaf rosettes about 1-3 cm wide and less than 5 cm tall. During the summer months the uppermost rosette leaves curve upward and become dormant, surrounding the growing tip. Reproductive leaf rosettes vary from 10-15 cm wide, and bear single erect racemes with small white to lavender flowers.

Participating Institutions
Updates
  • 09/01/2020
  • Orthodox Seed Banking

Based on an September 2020 extract of the California Plant Rescue Database, Santa Barbara Botanic Garden holds 25 accessions of Boechera hoffmannii in orthodox seed collection. There are as many as 59916 seeds of this species in their collection - although some may have been used for curation testing or sent to back up.

  • 09/01/2020
  • Orthodox Seed Banking

Based on an September 2020 extract of the California Plant Rescue Database, California Botanic Garden holds 4 accessions of Boechera hoffmannii in orthodox seed collection. There are as many as 308275 seeds of this species in their collection - although some may have been used for curation testing or sent to back up.

  • 09/01/2020
  • Orthodox Seed Banking

Based on an September 2020 extract of the California Plant Rescue Database, National Laboratory for Genetic Resource Preservation (USDA-ARS) holds 1 accessions of Boechera hoffmannii in orthodox seed collection. There are as many as 2500 seeds of this species in their collection - although some may have been used for curation testing or sent to back up.

  • 08/30/2020
  • Reproductive Research

Ongoing research by the Santa Barbara Botanic Garden has focused on reproductive biology and ecological requirements. Seedling cohorts show high mortality. Short-term drought, caused by high temperatures and lack of a maritime layer, has limited survival of seedlings and one-year old plants in some years since 1995. Most reproductive plants occur in close proximity to shrubs, suggesting that shade is important to survival during the first 2 years of growth. (Wilken 1996)

  • 08/05/2020
  • Seed Collection

Based on an August 2020 extract of the California Plant Rescue Database, Santa Barbara Botanic Garden has collected 26 seed accessions of Boechera hoffmannii from 5 plant occurrences listed in the California Natural Diversity Database. These collections together emcompass 356 maternal plants

  • 08/05/2020
  • Seed Collection

Based on an August 2020 extract of the California Plant Rescue Database, California Botanic Garden has collected 3 seed accessions of Boechera hoffmannii from 1 plant occurrences listed in the California Natural Diversity Database. These collections together emcompass 13 maternal plants

Nature Serve Biotics
  • 05/02/2017

Historically reported from at least 3 of the Channel Islands off the southern California coast. Currently, the species is known from only 6 small populations on Santa Cruz Island and ~10 plants on Santa Rosa Island. The Anacapa Island pop is historic. Although 2 of the Santa Cruz sites are fairly inaccessible, the tiny populations are somewhat vulnerable to destruction by introduced feral pigs and are threatened by invasive non-native annuals such as fennel (Foeniculum vulagre). Non-native sheep, which drastically altered the island's ecosystems over the past 150 years, have now been removed from the area. All the northern Channel Islands have suffered profound loss and degradation of their soils and changes in their plant communities due to large numbers of non-native mammals introduced to the islands starting in the early 1800's.

Dieter Wilken, Ph.D.
  • 01/01/2010

As listed in the recovery plan for thirteen plant taxa from the northern channel islands (USFWS 2000): Feral pig rooting activities directly affecting the Hoffman's rock cress plants. Soil erosion following feral pig activity indirectly affecting the

Dieter Wilken, Ph.D.
  • 01/01/2010

Only 3-4 populations are known; 2-3 on Santa Cruz Island and one on Santa Rosa Island. The largest population, with an annual average of 30 reproductive individuals, occurs on Santa Cruz Island. The remaining populations are composed of 0-5 reproductive individuals in any one year. A third locality on Santa Cruz Island has remained inaccessible and unmonitored for at least 5 years.

Dieter Wilken, Ph.D.
  • 01/01/2010

Ongoing research by the Santa Barbara Botanic Garden has focused on reproductive biology and ecological requirements. Seedling cohorts show high mortality. Short-term drought, caused by high temperatures and lack of a maritime layer, has limited survival of seedlings and one-year old plants in some years since 1995. Most reproductive plants occur in close proximity to shrubs, suggesting that shade is important to survival during the first 2 years of growth. (Wilken 1996)

Dieter Wilken, Ph.D.
  • 01/01/2010

Santa Rosa Island is managed by the National Park Service. The population on Santa Rosa Island occurs on a narrow ledge near a road. Sites on Santa Cruz Island occur on lands owned and managed by The Nature Conservancy. The latter, in cooperation with the National Park Service, is developing a plan for feral pig removal and reduction of exotic weeds. However, no short-term measures have been taken to protect populations from pig rooting.

Dieter Wilken, Ph.D.
  • 01/01/2010

Protection of current populations on Santa Cruz Island. Genetic analyses of populations, including variation among annual cohorts. Collection of seeds from the population on Santa Rosa Island. Surveys for undiscovered populations and for sites suitable for reintroduction.

Dieter Wilken, Ph.D.
  • 01/01/2010

Studies of seed longevity under both short-term and long-term cold storage conditions.

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Photos
Nomenclature
Taxon Boechera hoffmannii
Authority (Munz) Al-Shehbaz
Family Brassicaceae
CPC Number 178
ITIS 823126
USDA ARHO
Common Names Hoffmann's rock cress | Hoffmann's rockcress
Associated Scientific Names Arabis hoffmannii | Arabis maxima var. hoffmannii | Boechera hoffmannii
Distribution Santa Cruz and Santa Rosa Islands, Santa Barbara County, California. A historic report from Anacapa Island has not been substantiated and is probably erroneous.
State Rank
State State Rank
California S1S2
Habitat

Sandy to rocky soils of open sites in coastal shrublands, often on ledges or cliff ledges. Associated species include Coreopsis gigantea, Hazardia detonsa, Eriogonum arborescens, and Adenostoma fasciculatum at one site. Populations are found near the coast, usually where summer fog dominates during the late afternoon or night.

Ecological Relationships

Plants require fine-grained soils, shade, and summer moisture from foggy nights. Plants are self-compatible. Flowers are capable of self-pollination but insect visitation, mostly by bee flies (Bombyliidae), enhances seed set. Average plants produce about 3,000 light seeds, which are dispersed by wind as the fruits slowly dehisce. (Wilken 1995)

Pollinators
Common Name Name in Text Association Type Source InteractionID

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