Kenwood Marsh Checker-mallow

Sidalcea oregana ssp. valida

Description

Edward L. Greene first described Sidalcea oregana ssp. valida (Kenwood Marsh checker-mallow) on June of 1894 from material he collected from Knight's Valley, Sonoma County, California. This taxon has been known since then as S. maxima, S. oregana var. spicata, S. eximia, and S. spicata ssp. valida. C. L. Hitchcock studied the genus Sidalcea and recognized four subspecies in 1957, including S. oregana ssp. valida, a treatment accepted by Steven Hill in 1993.

S. oregana ssp. valida is a perennial herb in the mallow family (Malvaceae) with rounded leaves that grows 3-6 ft (1-2 m) tall. Lower leaves have five to seven shallow lobes, while upper leaves are generally smaller and divided into three to five entire, lanceolate segments. The compound inflorescence consists of densely flowered, spikelike racemes 0.8-2.0 in (2-5 cm) long. Petals are 0.4-0.6 in (1.0-1.5 cm) long, notched at the apex, and deep pink-mauve. The flowers appear from late June to September. S. oregana ssp. valida differs from S. oregana ssp. eximia in having a hairless calyx.

Habitat

S. oregana ssp. valida inhabits freshwater marshes approximately 490 ft (150 m) in elevation.

Distribution

S. oregana ssp. valida was never abundant according to record. Only two occurrences—18 mi (29 km) apart in Sonoma County—are known, both on private land. One population of less than 100 plants in 1979 and about 60 plants in 1993 covers less than 0.25 acres (0.1 hectares). The other population contained approximately 70 individuals in 1993.

Threats

S. oregana ssp. valida is threatened by the potential alteration of hydrology from urbanization and water withdrawal, by trampling and reduced seed set resulting from cattle grazing, competition from invasive plant species, and periodic aqueduct maintenance. This species is also susceptible to adverse impacts from random events.

One of the two remaining sites of S. oregana ssp. valida is threatened by both permitted and unauthorized water diversions from a stream that flows into the marsh where two subpopulations of the species occur. In the past, these diversions have removed all water from the stream channel, eliminating a source of surface water to the marsh. Plant census data from 1991 indicate that the eastern and western subpopulations in the marsh declined by approximately 40% and 30% respectively, when compared to 1989 and 1990 data. These figures suggest that this population may have been experiencing a delayed response to a drought period that began in the late 1980s. The adverse effects of future droughts may be exacerbated by increased surface water diversions that could result in the further decline or even the extinction of the species. The potential for loss of this population from naturally occurring events because of its small size would be much increased by the stress of future water diversions and droughts.

S. oregana ssp. valida is adversely affected at both of its locations by reduced seed set resulting from cattle grazing.

This taxon is being encroached upon by the invasive weeds common tule (Scirpus acutus ), yellow starthistle (Centaurea solstitialis ), and blackberry.

One of the subpopulations of this species was damaged by an off-road vehicle during maintenance of a local aqueduct that passes through the marsh. The maintenance activity occurred late in the season when the soil was relatively dry, resulting in minimal damage to the plants. Such maintenance activities occurring during a time when the soil is saturated would pose a threat to the plants.

No evidence of overcollection of S. oregana ssp. valida by botanists and horticulturists for scientific and commercial purposes is known at this time, although the species is considered to have horticultural potential. Both populations are small enough that even limited collecting pressure would have adverse consequences. S. oregana ssp. valida is an attractive plant, one that might be sought for collection once its rarity and current sites of occurrence become common knowledge. Wild collected seed of S. oregana sp. are available internationally through a seed exchange program offered by the North American Rock Garden Society.

Conservation and Recovery

California Department of Fish and Game has proposed to purchase approximately 90 acres (37 hectares) of the marsh where S. oregana ssp. valida occurs to create an ecological preserve. Acquisition of the preserve, is dependent, however, on the cooperation of the current landowners. The owner of one parcel with about half of the population has declined to sell her property to the state. Purchase of the land as a preserve would ensure appropriate grazing practices on the site and would allow direct management of the plant population with possible opportunities to expand the population. The preserve would include only a small portion of the watershed though, limiting the protection that the preserve would afford to the hydrology of the marsh.

Contact

U. S. Fish and Wildlife Service
Regional Office, Division of Endangered Species
Eastside Federal Complex
911 N. E. 11th Ave.
Portland, Oregon 97232-4181
Telephone: (503) 231-6121
http://pacific.fws.gov/

Reference

U. S. Fish and Wildlife Service. 22 October 1997. "Determination of Endangered Status for Nine Plants From the Grasslands or Mesic Areas of the Central Coast of California." Federal Register 62 (204): 54791-54808.