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.

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.

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

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

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.

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.

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.

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.

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.

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.

Development of an adequate and representative conservation seed collection.