Endangered Species in Santa Cruz County - Species Account


Scotts Valley Spineflower
(Chorizanthe robusta var. hartwegii)


This information was excerpted from the following publication, which is available for reference use at the Central Branch Library:


Because of the sheer number of spineflower species in California and the character used to distinguish them, even experienced botanists may have difficulty with their taxonomy. The two spineflowers in this plan [Ben Lomond spineflower and Scotts Valley spineflower] are varieties of closely related species that are both included in the Pungentes section (subdivision) of the genus Chorizanthe.

The Service listed the entire species of Chorizanthe robusta at the same time (U.S. Fish and Wildlife Service 1994), including the Santa Cruz Mountain variety covered in this recovery plan, the Scotts Vally spineflower (Chorizanthe robusta var. hartwegii). Chorizanthe robusta var. robusta (robust spineflower) occurs along the coastal and near-coastal areas of Santa Cruz and northern Monterey counties and will be covered in a separate recovery plan.

The Service listed the varieties of Chorizanthe pungens separately (U.S. Fish and Wildlife service 1992, 1994). The Santa Cruz Mountains variety, Chorizanthe pungens var. hartwegiana (Ben Lomond spineflower) is included in this recovery plan. Chorizanthe pungens var. pungens, which occurs along the coastal areas of Santa Cruz and northern Monterey counties, was listed as threatened and is treated in a recovery plan with six other plant species and the Myrtle's silverspot butterfly (U.S. Fish and Wildlife Service 1997c).1

Recovery Priority 3C —

Indicates a species having a high degree of threat, a high recovery potential, and is, or may be, in conflict with construction or other development projects.

Description and Taxonomy

Hartweg originally collected this taxon in 1847. James Reveal and Randall Morgan published the combination Chorizanthe robusta var. hartwegii (Reveal and Morgan 1989). Scotts Valley spineflower is an annual species in the buckwheat family. The plant grows to 3 decimeters (12 inches) high and has an erect rather than prostrate habit. The rose-pink color on the margins of the bracts below the flowers is confined to the basal portion of the teeth. The medium-sized heads (1.0-1.5 centimeters (0.4-0.6 inch) in diameter) are distinctly clustered.

Life History

Scotts Valley spineflower is a short-lived annual species. This plant has not been the subject of specific studies other than population monitoring.

Habitat Description

Scotts Valley spineflower is endemic to Purisima sandstone and Santa Cruz mudstone in Scotts Valley in the Santa Cruz Mountains. Where Scotts Valley spineflower occurs on Purisima sandstone, the bedrock is overlain with a thin soil layer that supports a meadow community that includes herbs and low-growing grasses. The presence of certain associate species, such as toad rush (Juncus bufonis), sand pigmyweed (Crassula erecta), mosses, and lichens suggest a high seasonal moisture content. Where the plant occurs on Santa Cruz mudstone, the bedrock is variously mixed with scree (small stones or rock debris) or a thin soil layer supporting a meadow community of herbs and grasses, though of somewhat different composition than those on Purisima sandstone and with a lesser frequency of toad rush, pigmyweed, and lichens (Habitat Restoration Group 1992). Scotts Valley polygonum occurs in close proximity to Scotts Valley spineflower at several sites.

Range and Distribution

Virtually the entire range of the Scotts Valley spineflower occurs on four parcels, all in private ownership, and covers a range of 1.5 miles in northern Scotts Valley.

Population Status and Current Threats

In 1990, the total population of Scotts Valley spineflower was estimated to be about 300,000 individuals, but recent estimates have been much lower (CNDDB 1998, Denise Duffy and Associates 1997). These fluctuations in numbers of this short-lived annual most likely have been tied to changes in climatic conditions.

Over the last 5 years, a variety of housing proposals have been considered for three of the parcels, and a fourth parcel was recently sold by Borland International to Greystone Homes for development. Scotts Valley spineflower is threatened by the destruction of a portion of currently occupied habitat associated with the proposed construction of a high school and two proposed residential developments and by secondary impacts, including alteration of the remaining habitat by trampling, introduction of nonnative species, the application of herbicides, pesticides and fertilizers, and alteration of the surrounding hydrologic regime.

Conservation Efforts

Each of the proposals for development has included plans for setting aside preserve areas primarily for Scotts Valley spineflower and, to some extent, for Scotts Valley polygonum (City of Scotts Valley 1991, Harding Lawson Associates 1991); however, the Service believes that preserve designs have been inadequate to maintain the long-term viability of the populations of either the spineflower or the polygonum (U.S. Fish and Wildlife Service, in litt. 1992, 1993).

Needed Recovery Actions

Specific recovery actions for Scotts Valley spineflower include:

  • Protection through acquisition of habitat or establishment of conservation easements,
  • Habitat Conservation Plan with the City of Scotts Valley that minimizes disturbance from urban development, and
  • Conduct research focusing on habitat requirements for long-term survival.2

Footnotes

1U.S. Fish and Wildlife Service. "Recovery Plan for Insect and Plant Taxa from the Santa Cruz Mountains in California." Portland, Oregon." The Service, 1998, pp.25-26.

2Ibid., pp. 29-31.