Antioch Evening Primrose
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Sacramento Fish & Wildlife Office

Species Account

ANTIOCH DUNES EVENING-PRIMROSE
(Oenothera deltoides ssp. howellii)

CLASSIFICATION:Federal Endangered Species (Federal Register 43:17910 (pdf); April 26, 1978)

CRITICAL HABITAT:  Designated in Federal Register  43:39042; August 31,1978
[Notice not available online. See Code of Federal Regulations section on plants.]

T.2N., R.2E., SW 1/4 of Section 17, and E 2/3 of S 1/3 of Section 18 (Mt. Diablo Meridian), Contra Costa County (see map)

RECOVERY PLAN: Revised recovery plan for three endangered species endemic to Antioch Dunes, California. 1984

DESCRIPTION:

Antioch Dunes evening-primrose(ssp. howellii) is a short-lived perennial plant in the evening-primrose family (Onagraceae). It forms large tufts with coarse drooping stems 4-40 inches long, much branched.

Leaves are lance-like in outline, 1-5 inches long, 0.4-1.2 inches wide, grayish with numerous short and fewer longer hairs. White flowers bloom from March to September. Petals are about one inch long. Stamens are yellow. The species can be confused with Oenothera deltoides ssp. cognata, which grows in the Oakley area southeast of the dunes. See Hickman (1993) in General Information about California Plants, below, for a detailed description of each species.

DISTRIBUTION:

The subspecies now occurs in several locations near the confluence of the Sacramento and San Joaquin Rivers. The only natural stands exists within the sand dunes near Antioch in Contra Costa county.

Most of the natural dune habitat is in Antioch Dunes National Wildlife Refuge (administered by the Don Edwards San Francisco Bay National Wildlife Refuge Complex). There are two other endangered species, Contra Costa wallflower (Erysimum capitatum var. angustatum) and Lange's metalmark butterfly (Apodemia mormo langei) near Antioch.

The subspecies has been transplanted to Brannan Island State Recreation Area. There are also two small colonies on Brown's Island in Contra Costa County. The most recently discovered population is located on private property north of Oakley. 

The historic range of Oenothera deltoides ssp. howellii is unknown and open to speculation. Presumably it was limited to the sandy soil type (Oakley or Delhi sand) found at the dunes and over a substantial portion of eastern Contra Costa County. Nevertheless, no known evidence demonstrates that the subspecies historically occupied any area other than the Antioch Dunes proper.

THREATS:

In the early 1900's, the isolated dune habitat in the delta began to experience a dramatic change as human development expanded. The easily-accessible sand was harvested to make bricks. Large-scale sand mining and industrial development fragmented the sand dune habitat until only a small portion of the original ecosystem remained. Non-native grasses and vegetation encroached on the sand dunes to crowd the few remaining endangered plants.

By the time the Antioch Dunes National Wildlife Refuge was established, only a few acres of remnant dune habitat supported the last natural populations of Antioch Dunes evening-primrose, Contra Costa wallflower, and Lange's metalmark butterfly.

A reservoir of moving sand is essential to maintain the dynamic ecology of the dunes, as moving sand opens areas for the establishment of seedling plants. Roto-tilling has contributed to the invasion of exotic vegetation that stabilizes the remaining sand-dune habitat and competes with native dune vegetation.

Habitat improvement activities have included dune restoration, hand-clearing nonnative plant species, planting buckwheat seedlings and restriction of public access to avoid trampling and fire.

STATE & CALIFORNIA NATIVE PLANT SOCIETY STATUS:

This species was listed as endangered by the California Department of Fish and Game in November 1978. The California Native Plant Society has placed it on List 1B (rare or endangered throughout its range).

MORE INFORMATION ABOUT THIS SPECIES:

Anonymous. 1971. Antioch primrose sown out of range. Four Seasons 4(1):21.

Howard, A. Q., and R. A. Arnold. 1980. The Antioch Dunes - Safe at last? Fremontia 8:3-12.

Klein, W. M. 1962. New taxa and recombinations in Oenothera (Anogra). Aliso 5:179-180.

Klein, W. M. 1970. The evolution of three diploid species of Oenothera subgenus Anogra (Onagraceae). Evolution 24:578-579.

Munz, P. A. 1931. Studies in Onagraceae VI. The subgenus Anogra of the genus Oenothera. Amer. J. Bot. 18:314.

Roof, J. B. 1969. In memoriam: The Antioch Dunes. Four Seasons 3(1):2-4

U.S. Fish and Wildlife Service. 1978a. Final Determination that Eleven Plant Taxa are Endangered and Two Plant Taxa are Threatened Species. Washington, DC

U.S. Fish and Wildlife Service. 1978b. Determination of Critical Habitat for Two California Plants. Washington, DC.

U.S. Fish and Wildlife Service. 1984. Revised recovery plan for three endangered species endemic to Antioch Dunes, California. Portland, OR.

General Information about California Plants

Photo credit: Antioch evening primrose, Walter Knight © California Academy of Sciences, Calphoto ID: 8253 3202 0971 0028

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

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