Endangered Species in Santa Cruz County - Species Account


Ben Lomond Spineflower
(Chorizanthe pungens var. hartwegiana)


This information was taken from the following publications, which are available for reference use at the Central Branch Library:


A Note on the Taxonomy of Chorizanthe

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

At the time of listing, the Service listed the entire species of Chorizanthe robusta, inclusive of both varieties. The Santa Cruz Mountains variety, C. robusta var. hartwegii is included in this recovery plan. The other variety which occurs along the coastal and near-coastal areas of Santa Cruz and northern Monterey counties, C. robusta var. robusta, will be treated in a separate recovery plan.

At the time of listing, the Service listed the varieties of Chorizanthe pungens separately. The Santa Cruz Mountains variety, C. pungens var. hartwegiana, is included in this recovery plan. The other variety, which occurs along the coastal areas of Santa Cruz and northern Monterey counties, C. pungens var. pungens, is treated in a recovery plan along with six other plant taxa and the Myrtle's silverspot butterfly. That recovery plan is currently [1997] out for public review.1

Recovery Priority 9 —

Indicates a subspecies having a moderate degree of threat and a high recovery potential.

Description and Taxonomy

Chorizanthe pungens was first described by George Bentham in 1836 based on a specimen collected in Monterey. This taxon was recognized by George Goodman in 1934 as the type species in describing the Pungentes section of the genus. Chorizanthe pungens var. hartwegiana was distinguished from C. pungens var. pungens by James Reveal and Clare Hardham (1989) based on a distinction between the coastal form and an inland form 'in the Ben Lomond sand hills area.

Ben Lomond spineflower is a small annual herb in the buckwheat family (Polygonaceae). The plants grow up to 2.5 decimeters (10 inches) high. Whorls of bracts (involucres) below the flowers are 1.5-2.5 millimeters (0.6-1.0 inch) long and have pink scarious (thin and dry) margins. The tepals (undifferentiated petals and sepals) are irregularly toothed at the tips. Compared to other species in the pungens-robusta complex, Ben Lomond spineflower is more erect and the flower clusters and associated structures (inflorescences) are pink with small distinct heads (Ertter 1996).

Life History

Ben Lomond spineflower is a short-lived annual species. Seeds germinate in late fall after the first substantial rains. The plants mature through the winter and then bolt and produce branches, flower in April and May, and die soon after seed production in June (McGraw and Levin 1994). The life span of the plant ranges from 15 to 21 weeks, with most of the variability coming during the adult stage. It is pollinated by a variety of insects, including wasps, bees, flies, and butterflies (R. Morgan, pers. comm. 1997).

Several studies carried out by students at the University of California at Santa Cruz have contributed to our knowledge of the species (Pollock 1995, Kluse 1994, Hames et al. 1993, McGraw and Levin 1994). Biomass and seed set varied with site conditions in a controlled experiment with plants transplanted into grass, manzanita, and pine sites. Seed set varied from none to about 60 seeds per plant, with an overall average of 8 seeds. Higher performance was closely tied to the lack of shading; the highest seed sets and survivals were in unshaded or open pine forests and the lowest under silver-leafed manzanita canopies (Kluse 1994). In another controlled experiment, potted seedlings were subjected to various soil and shade treatments. Plants grown in full sun flowered earlier than those in low shade or high shade; however, plants in low shade produced more flowers than either those in full sun or high shade (McGraw and Levin 1994).

Habitat Description

Ben Lomond spineflower is found on sandy Zayante soils that are the basis for the Ben Lomond sandhills communities in the Santa Cruz Mountains. This species is frequently found in association with Ben Lomond wallflower and other species restricted to the sandhills habitat. McGraw and Levin (1994) found that survivorship of potted individuals was more strongly tied to shade treatment (with highest survivorship under low shade, and lowest survivorship under high shade) than to soil treatment. Of the five soil treatments (sand, manzanita, pine, redwood, oak), all measures of performance were highest for plants grown in the four soils where spineflowers do not naturally occur. These results indicate the Ben Lomond spineflower is not restricted to sandy soils due to any chemical, physical, or biological requirements, but is intolerant of shade and unable to compete for light with other species that commonly occur on the nonsandy soils.

Range and Distribution

Most occurrences of Ben Lomond spineflower are found in the area generally bounded by the communities of Ben Lomond, Glenwood, Scotts Valley, and Felton. Outlying populations are located near Bonny Doon, Boulder Creek, Big Basin State Park, and Gray Whale Ranch State Park.

Population Status and Current Threats

Sand quarrying has resulted in the direct removal of the plant's habitat, and a currently proposed expansion of operations at Quail Hollow Quarry will eliminate additional populations (Thomas Reid Associates 1997). Residential development on smaller parcels of privately owned lands has also contributed to the elimination of Ben Lomond spineflower and the fragmentation of the remaining habitat.2

Conservation Efforts

Protective management for sandhill parkland communities will be developed for one parcel adjacent to Quail Hollow Ranch which was recently acquired by the State of California. Management plans for Quail Hollow Ranch are being developed by the County of Santa Cruz (County); proposed recreational facilities may affect populations of both the Chorizanthe pungens var. hartwegiana and Erysimum teretifolium (County of Santa Cruz 1990). A few small populations also occur within Big Basin and Henry Cowell State Parks, but there are no specific management prescriptions for this taxon at this time (George Gray, Ecologist, California Department of Parks and Recreation, pers. comm. 1997). The Quail Hollow Quarry HCP [Habitat Conservation Plan] includes conservation of North Ridge, which supports this species and other sandhills species.

Needed Recovery Actions

The general strategies discussed in the Overall Recovery Strategy section are appropriate for this species. In particular, this species will benefit from:

  • HCP with the County of Santa Cruz that minimizes the loss of habitat from sand mining and urban development3
  • Develop and implement appropriate management actions for State-owned units (Big Basin State Park, Henry Cowell Redwoods State Park, and Gray Whale Ranch State Park). (A management plan for Quail Hollow Ranch County Park is under development and California Department of Fish and Game is currently developing a final management plan for Bonny Doon Ecologic Reserve.)
  • Research focusing on habitat requirements for long-term survival, and
  • Manage for reduction of competition from nonnative annual grasses and to minimize or prevent invasion of native woody species into open habitats.4

Footnotes

1U.S. Fish and Wildlife Service. Draft Recovery Plan for Two Insects (Polyphylla barbata and Trimerotropis infantilis) and Four Plants (Chorizanthe pungens var. hartwegiana, Chorizanthe robusta var. hartwegii, Erysimum teretifolium, and Polygonum hickmanii) from the Santa Cruz Mountains, California." Portland, Oregon. The Service, 1997, pp.23-24.

2U.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. 28-28.

3U.S. Fish and Wildlife Service. Draft Recovery Plan for Two Insects (Polyphylla barbata and Trimerotropis infantilis) and Four Plants (Chorizanthe pungens var. hartwegiana, Chorizanthe robusta var. hartwegii, Erysimum teretifolium, and Polygonum hickmanii) from the Santa Cruz Mountains, California." Portland, Oregon. The Service, 1997, pp.25-26.

4U.S. Fish and Wildlife Service. "Recovery Plan for Insect and Plant Taxa from the Santa Cruz Mountains in California." Portland, Oregon." The Service, 1998, p. 28.