CPC Plant Profile: Gambel's Watercress
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Plant Profile

Gambel's Watercress (Nasturtium gambelii)

Flowering Rorippa gambellii Photo Credit: Dieter Wilken
Description
  • Global Rank: G1 - Critically Imperiled
  • Legal Status: Federally Endangered
  • Family: Brassicaceae
  • State: CA
  • Nature Serve ID: 146000
  • Date Inducted in National Collection: 10/16/2004

Once found from San Luis Obispo County south to San Bernardino County, California, and in central Mexico, Gambels watercress today is known from only three localities in the United States, and its numbers have dwindled to perhaps less than 300 individuals. Known from about 8 occurrences in the United States at the time it was listed in 1993, the number of extant populations has dwindled to only three in southern San Luis Obispo County and western Santa Barbara County (Anonymous 2008a; Parikh et al. 1998). At one of these localities, it co-occurs with marsh sandwort (Arenaria paludicola), another endangered species. The last and only report made for San Bernardino County was in 1935 at Urbita Hot Springs, currently the site of a mall next to the Orange Show Fairgrounds in San Bernardino. An early report from the mountains of San Diego County has not been confirmed (Anonymous 2008b). Although reported from Mexico, its status there is unknown (Wickenheiser, L.P. 1989). Gambels watercress (Rorippa gambelii, Cardamine gambelii in literature) is probably best treated as a species of Nasturtium (Al-Shehbaz and Price 1998). Gambels water cress is an aquatic, herbaceous perennial, producing floating and emergent stems (Abrams and Ferris 1944; Mason 1957; Rollins 1993; Al-Shehbaz and Price, 1998). Vegetative shoots often sprawl over associated vegetation and have been reported to reach up to 1 meter in length, bearing pinnately compound leaves. Vegetative shoots can spread and produce new plants adventitiously. The flowering shoots produce terminal clusters of white flowers. Flowers are about 1 cm wide at anthesis, and bear the 4 white petals and 6 stamens typical of a mustard. Each fruit can produce up to 20 seeds, which are yellowish- to reddish brown in color. Flowering ranges from April through July. Plants of Gambels watercress have been confused with the introduced watercress (Rorippa nasturtium-aquaticum = Nasturtium officinale). These two species are also known to hybridize at one remaining occurrence, making identification more difficult, and also resulting in a potential threat from the apparently more competitive hybrid.

Participating Institutions
Updates
  • 09/19/2020
  • Propagation Research

Studies of plants at the Santa Barbara Botanic Garden have provided mixed results regarding the breeding system. Overall, flowers are self-compatible, but seed set, relative to a larger number of ovules, is enhanced by augmented pollination, suggesting that visitation by insects are important to pollination in nature

  • 09/19/2020
  • Propagation Research

Experimental studies have shown that Gambels watercress propagates readily from seeds and from vegetative cuttings, using single shoots bearing adventitious roots at the base.

  • 09/19/2020
  • Living Collection

The Santa Barbara Botanic Garden maintains a living collection of plants representing limited genetic diversity from one natural population and seed collections secured from one other occurrence, currently believed extirpated.

  • 09/01/2020
  • Orthodox Seed Banking

Based on an September 2020 extract of the California Plant Rescue Database, Santa Barbara Botanic Garden holds 11 accessions of Nasturtium gambelii in orthodox seed collection. There are as many as 460 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 3 accessions of Nasturtium gambelii in orthodox seed collection. There are as many as 1017 seeds of this species in their collection - although some may have been used for curation testing or sent to back up.

  • 08/05/2020
  • Seed Collection

Based on an August 2020 extract of the California Plant Rescue Database, Santa Barbara Botanic Garden has collected 11 seed accessions of Nasturtium gambelii from 4 plant occurrences listed in the California Natural Diversity Database. These collections together emcompass 9 maternal plants

  • 08/05/2020
  • Seed Collection

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

Nature Serve Biotics
  • 05/02/2017

Known from about 4 small extant populations: 3 in San Luis Obispo County and 1 or 2 in adjacent Santa Barbara County, California. There are fewer than 1700 individuals known to remain. Historically, the species was known from 4 other sites in southern coastal California, and from 1 very disjunct site near Mexico City, Mexico; populations at these sites have likely been extirpated by development and draining. Existing populations are primarily threatened by competition with exotic species and the potential for development of the little remaining suitable habitat.

Dieter Wilken
  • 01/01/2010

Loss of wetlands and sporadic inundation of stable wetland habitats. Competition from alien invasives. Hybridization with the common European watercress (Nasturtium officinale). Eutrophication resulting from increased nutrient levels.

Dieter Wilken
  • 01/01/2010

Among approximately 8 historic occurrences, only three are believed to be extant. As recently as 1998, the number of individual plants at extant sites was collectively estimated to be fewer than 1000 flowering shoots (Anonymous 2008b). However, the number of genetically distinct plants remains unknown, and probably are fewer.

Dieter Wilken
  • 01/01/2010

Experimental studies have shown that Gambels watercress propagates readily from seeds and from vegetative cuttings, using single shoots bearing adventitious roots at the base. Studies of plants at the Santa Barbara Botanic Garden have provided mixed results regarding the breeding system. Overall, flowers are self-compatible, but seed set, relative to a larger number of ovules, is enhanced by augmented pollination, suggesting that visitation by insects are important to pollination in nature Field studies of potential suitable habitat are being conducted by the US Fish and Wildlife Service.

Dieter Wilken
  • 01/01/2010

One natural population at Oso Flaco Lake in San Luis Obispo County occurs on lands owned by the State of California, and is managed by State Park staff. Another population on Vandenberg Air Force Base, Department of Defense, is managed by base environmental staff. The Santa Barbara Botanic Garden maintains a living collection of plants representing limited genetic diversity from one natural population and seed collections secured from one other occurrence, currently believed extirpated.

Dieter Wilken
  • 01/01/2010

Currently the highest priority for further research and management depends on the identification of suitable habitats where experimental recovery projects can be implemented, especially to determine limits and requirements of population stability. The number of distinct genetic strains needs to be estimated, using molecular markers.

Dieter Wilken
  • 01/01/2010

Development of an adequate and representative conservation seed collection.

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Photos
Nomenclature
Taxon Nasturtium gambelii
Authority (S. Watson) O.E. Schulz
Family Brassicaceae
CPC Number 44446
ITIS 517470
USDA NAGA
Common Names Gambel's Watercress | Gambel's yellowcress
Associated Scientific Names Rorippa gambelii | Nasturtium gambelii | Cardamine gambelii | Cardamine gambellii | Rorippa gambellii
Distribution From southern San Luis Obispo County south to San Bernardino County, California, and in central Mexico.
State Rank
State State Rank
California S1
Habitat

Gambels watercress occurs naturally in open or semi-shaded sites along the edges of permanent, slow-moving streams and at the edges of freshwater marshes or lakes. The typical substrate is sandy, saturated, and with a high organic content. Gambels watercress has been associated with such riparian species as bur-reed (Sparganium), tules (Scirpus), rushes (Juncus), cattails (Typha), wax myrtle (Myrica californica), reed-grass (Calamagrostis), and arroyo willow (Salix lasiolepis). Observations of its growth at the Santa Barbara Botanic Garden confirm its need for a constant source of fresh water. Studies of soil seed banks at one locality demonstrated a viable natural seed bank, based on observations of germinating seedlings, but seed age could not be determined (Mazer and Waddell 1994; Mazer 2000).

Ecological Relationships

Gambels watercress occurs naturally in open or semi-shaded sites along the edges of permanent, slow-moving streams and at the edges of freshwater marshes or lakes. The typical substrate is sandy, saturated, and with a high organic content. Gambels watercress has been associated with such riparian species as bur-reed (Sparganium), tules (Scirpus), rushes (Juncus), cattails (Typha), wax myrtle (Myrica californica), reed-grass (Calamagrostis), and arroyo willow (Salix lasiolepis). Observations of its growth at the Santa Barbara Botanic Garden confirm its need for a constant source of fresh water. Studies of soil seed banks at one locality demonstrated a viable natural seed bank, based on observations of germinating seedlings, but seed age could not be determined (Mazer and Waddell 1994; Mazer 2000).

Pollinators
Common Name Name in Text Association Type Source InteractionID
Other
Thrips Thysanoptera Pollen Robber Link

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