Oenothera deltoides subsp. howellii
|Oenothera deltoides subsp. howellii|
|Subspecies:||O. deltoides subsp. howellii|
|Oenothera deltoides subsp. howellii
Oenothera deltoides subsp. howellii is a short-lived perennial plant with thick stems varying from 4 to 40 inches in length. It is multi-branching in form and tends to grow in large tufts. The grayish colored leaves are shaped like a lance and are about 1 to 5 inches long with many hairs, primarily short with only a few being longer. Its flowers are white with inch-long petals and yellow stamens. It blooms from March to September. The subspecies is often confused with Oenothera deltoides ssp. cognata that grows in an area southeast of the protected area.
Distribution and habitat 
Oenothera deltoides subsp. howellii is a perennial plant that grows only in an environmentally sensitive sand dune habitat located near the meeting of the Sacramento River and the San Joaquin River in California.
In 1979 Oenothera deltoides subsp. howellii, the Antioch Dunes Evening Primrose, was declared an endangered species. Currently, its habitat is restricted to the Antioch Dunes National Wildlife Refuge, the last remnant of an isolated nine kilometer stretch of sand dune habitat. The refuge was formed in 1980 to prevent extinction of this plant, as well as Lange's metalmark butterfly (Apodemia mormo langei) and the Contra Costa wallflower (Erysium capitatum var. angustatum). This refuge is the first national wildlife refuge in the U.S. formed to protect endangered plants and insects, and it is open for viewing to the public only under supervision because of the sensitive status of these species.
Endangered status 
- "Calflora Database - Species Search Results". www.calflora.org. Retrieved 2009-11-26.
- "Oenothera deltoides subsp. howellii (Antioch Dunes Evening-primrose) - GBIF Portal". data.gbif.org. Retrieved 2009-11-24.
- "Antioch Dunes evening-primrose species account from the Sacramento Fish & Wildlife Office". www.fws.gov. Retrieved 2009-11-23.
- Slack, Gordon. "Between River and Bay — Bay Nature Institute". baynature.org. Retrieved 2009-11-26.
- Sheppard, Mathew. "The Xerces Society » Sweat bees: Sphecodogastra antiochensis". www.xerces.org. Retrieved 2009-11-24.
- "Species Profile for Antioch Dunes evening-primrose (Oenothera deltoides howellii)". ecos.fws.gov. Retrieved 2009-11-24.
- "Antioch Dunes Evening-Primrose - Final Critical Habitat, USFWS [ds252]". www.atlas.ca.gov. Retrieved 2009-11-23.
- "Antioch Dunes National Wildlife Refuge, a California National Park near Antioch, Brentwood, Clayton, Coast Guard Isla, Concord". www.stateparks.com. Retrieved 2009-11-24.
- "Recreation.gov recreation area details - Antioch Dunes National Wildlife Refuge - Recreation.gov". www.recreation.gov. Retrieved 2009-11-24.
- "Endangered and Threatened Wildlife and Plants; Initiation of 5-Year Reviews of 58 Species in California and Nevada". frwebgate.access.gpo.gov. Retrieved 2009-11-24.
- Naumovich, Lech (April 16, 2007). "California Native Plant Society - USFWS 5 year review comments". PDF. California Native Plant Society. Retrieved 26 November 2009.
- "Article: Antioch Dunes National Wildlife Refuge (NWR).(Antioch, California)(Brief Article) - Endangered Species Bulletin". www.highbeam.com. Retrieved 2009-11-26. Text " HighBeam Research - FREE trial" ignored (help)
- Brian Czech, Paul Krausman (2001). "The Endangered Species Act: history, conservation biology, and public policy". books.google.com. Retrieved 2009-11-26.