Hoover's Spurge
See photo info below

Sacramento Fish & Wildlife Office
Species Account

HOOVER'S SPURGE
(Chamaesyce hooveri)

CLASSIFICATION: Federal Threatened Species (Federal Register 62:14338 pdf; March 26, 1997).

The California Native Plant Society has placed Hoover's spurge on List 1B (rare or endangered throughout its range). Although the species has not been officially listed by the State of California, the Department of Fish and Game considers it to be "very threatened."

CRITICAL HABITAT: Originally designated in Federal Register 68:46683 pdf; August 6, 2003.

The designation was revised in 70:46923 pdf; August 11, 2005.

Species by unit designations were published in 71:7117 | PDF February 10, 2006.

RECOVERY PLAN: Recovery Plan for Vernal Pool Ecosystems of California and Southern Oregon

DESCRIPTION:

Hoover's spurge (Chamaesyce hooveri), also known as Hoover's sanmat, is a prostrate, tap-rooted, annual herb in the spurge family (Euphorbiaceae). It forms mats from a few inches to a few feet across.

The flowering structure is a small, highly simplified cup-like "cyathium," as in all other spurges (Chamaesyce and Euphorbia). The flowering structure in Hoover's spurge has petal-like glands that are red to olive in color. Blooms appear in July.

This species is readily distinguished from other species of Chamaesyce by characteristics of growth habit, plant color and leaf shape. It is distinguished from plants in the genus Euphorbia on the basis of growth habit, vascular anatomy, and photosynthetic pathway.

Hoover's spurge grows in relatively large, deep vernal pools among the rolling hills, remnant alluvial fans and depositional stream terraces at the base of the Sierra Nevada foothills. It tends to occur where competition from other species has been reduced by prolonged seasonal inundation or other factors.

See Hickman (1993) in General Information about California Plants, below, for a detailed description of all of these species.

DISTRIBUTION:

The main remaining area of concentration for Hoover's spurge is in the northeastern Sacramento Valley. The Vina Plains of Tehama and Butte counties contains most of the known extant occurrences.

Another concentration is in the Southern Sierra Foothills, including the Visalia-Yettem area of Tulare County and the Hickman-La Grange area of Stanislaus County. Three other occurrences are on the Sacramento National Wildlife Refuge in Glenn County.

See a Hoover's spurge distribution map (PDF) from the draft recovery plan.

THREATS:

Habitat loss and fragmentation are the largest threats to the survival and recovery of vernal pool species. Loss of habitat generally results from urbanization, agricultural conversion and mining.

Habitat loss also occurs in the form of habitat alteration and degradation as a result of changes to natural hydrology, invasive species, incompatible grazing regimes, infrastructure projects (e.g., roads, water storage and conveyance, utilities), recreational activities (e.g., off-highway vehicles and hiking), erosion, contamination and inadequate management and monitoring.

Agricultural conversions are a continuing specific threat, particularly in Stanislaus County. Competition from invasive native and non-native plants threatens nine of the extant occurrences, including eight in the Vina Plains and one on the Sacramento National Wildlife Refuge in Glenn County.

Five of the remaining occurrences are subject to specific hydrological threats. Some specific threats also are continuing due to inappropriate livestock grazing practices.

REFERENCES FOR ADDITIONAL INFORMATION:

General Information about California Plants

Photo credit: Hoover's Spurge © 2003 George W. Hartwell Calphoto ID: 0000 0000 0603 0735

Prepared by Endangered Species Div., Sacramento Fish & Wildlife Office, U.S. Fish & Wildlife Service