The following Participating Institutions are custodians for this species in the CPC National Collection:
Rancho Santa Ana Botanic Garden
Santa Barbara Botanic Garden
The conservation of Arenaria paludicola is fully sponsored.
Dieter Wilken contributed to this Plant Profile.
Once found in Pierce County, Washington and from San Francisco Bay to the San Bernardino Valley in California, marsh sandwort today is known from fewer than three localities, and its numbers have dwindled to perhaps less than perhaps 50 individuals. As early as 1915, marsh sandwort was considered to be one the rarest plants in Washington, and throughout the first half of 20th Century, botanists stated that it had been seldom or rarely collected elsewhere (Abrams and Ferris 1944; Anonymous 2008a; Maguire 1951; Piper and Beattie, 1915; Wiegand, 1897). The only known locality in San Francisco Bay was near Fort Point (under the Golden Gate Bridge), where it was reported to be very abundant in swamps (Kellogg 1863). It has not been seen there since 1899. The last collection made in San Bernardino County was in 1899; the last observation at a single location in the Santa Cruz Mountains was in 1976. Today, marsh sandwort is known from as few as two localities in southern San Luis Obispo County. At one of these localities, it co-occurs with Gambels watercress, another endangered species. Marsh sandwort has been reported from Mexico and Guatemala, but its distribution there also appears to be highly restricted (Bonilla 1992; Hartman et al. 2005; Islebe 2003).
Marsh sandwort is a delicate herbaceous perennial, producing mat-like clusters of erect, slender shoots from underground runners (Abrams and Ferris 1944; Hartman et al. 2005; Hitchcock 1964; Mason 1957). The vegetative shoots often twine around each other or sprawl over associated vegetation and have been reported to reach up to 1 meter in length. Shoots typically have many pairs of opposite, linear leaves, with blades 1-2 cm long. The flowering shoots, which produce small, solitary, white flowers, often ascend among the leaves and stems of other marsh plants like rushes and sedges. Flowers are about 8-10 mm wide at anthesis, bear 5 white petals, and 10 stamens. Flowering is sporadic, ranging from May through August. Each flower produces a few, small, black seeds, but the type of potential pollinator remains unknown (Mazer and Waddell 1994; Mazer 2000).
Distribution & Occurrence
Marsh sandwort occurs naturally in open or semi-shaded sites, often as an emergent, along the edges of permanent, slow-moving streams and in freshwater marshes relatively close to the ocean. The typical substrate is sandy, saturated, and with a high organic content. In southern California it has been associated with such riparian species as rushes (Juncus), cattails (Typha), sedges (Carex), wax myrtle (Myrica californica), reed-grass (Calamagrostis), and arroyo willow (Salix lasiolepis). Observations of its growth at the Santa Barbara Botanic Garden and an experimental planting at a freshwater spring in San Luis Obispo County 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; Parikh et al. 1998).
Reported from Mexico and Guatemala.
|Among approximately 10 historic occurrences in Washington and California, only two are known to be extant on public or protected lands. As recently as 2005, the number of individual plants at these sites was collectively estimated to be fewer than 50 plants (Anonymous 2008c). The status on private lands has not been recently ascertained, but relatively few plants have been reported (Anonymous 2008c).|
Conservation, Ecology & Research
Competition from alien invasives.
Eutrophication resulting from increased nutrient levels.
Studies of plants at the Santa Barbara Botanic Garden have provided mixed results regarding the breeding system. Overall, flowers are weakly self-compatible, but seed set, relative to a larger number of ovules, is not enhanced by augmented pollination, suggesting the possibility of inbreeding depression.
Field studies of potential suitable habitat are being conducted by the US Fish and Wildlife Service.
The Santa Barbara Botanic Garden maintains a living collection of plants representing limited genetic diversity from one natural population and another presumed to be extirpated.
Genetic analyses of plants remaining in natural populations and plants held in living conservation collections.
Abrams, L.; Ferris, R. 1944. Illustrated flora of the Pacific states. Stanford University Press, California. 635p.
Anonymous. 2008b. Vascular plants, bryophytes, and lichens list. California Department of Fish and Game, Natural Diversity Database, Sacramento. Quarterly Publication. 70.
Anonymous. 2008c. California Natural Diversity Data Base. RareFind.Version 3.1.1. Sacramento. California Department of Fish and Game.
Hoover, R. 1970. The vascular plants of San Luis Obispo County, California. Berkeley. University of California Press. 350.
Mason, H.L. 1957. A flora of the marshes of California. Berkeley. University of California Press. 868.
Piper, C.; Beattie, R. 1915. Flora of the northwest coast. Lancaster, PA. New Era Printing Co. 418.
Thomas, J. 1961. Flora of the Santa Cruz Mountains, California. Stanford University Press, California. 434.