Based on an September 2020 extract of the California Plant Rescue Database, University of California Botanical Garden holds 1 accessions of Oenothera deltoides subsp. howellii in orthodox seed collection. We are uncertain as to how many total seeds are in this collection.
Based on an September 2020 extract of the California Plant Rescue Database, California Botanic Garden holds 25 accessions of Oenothera deltoides subsp. howellii in orthodox seed collection. There are as many as 442866 seeds of this species in their collection - although some may have been used for curation testing or sent to back up.
Based on an August 2020 extract of the California Plant Rescue Database, University of California Botanical Garden has collected 1 seed accessions of Oenothera deltoides subsp. howellii from 1 plant occurrences listed in the California Natural Diversity Database. These collections together emcompass an unknown number of maternal plants
Endemic to California's Antioch Dunes, Oenothera deltoides ssp. howellii is known only from three native occurrences in Contra Costa County. Recovery work is in progress and two occurrences have been introduced in Sacramento and Contra Costa County. The plant is seriously threatened by mining, agriculture, industrial development, and non-native plants.
Fire control activities
Off-road vehicles (ORV's)
Seven sites in the 70 acres along the San Joaquin River near Antioch, Contra Costa Co. Only three of these are naturally occurring populations--the other four are reintroduced populations. (Skinner 1997; NatureServe 2001)
Pavlik et al. studied the population biology of this species (Pavlik et al. 1988, 1993; Pavlik 1994)
A graduate student in Claremont Graduate School (Julie A. Greene) studied the reproductive ecology of this species (Greene 1995).
Recovery work is in progress and two occurrences have been introduced in Sacramento and Contra Costa County. (CDFG 2002)
The Antioch Dunes need to remain protected from activities that would degrade the habitat, and management activities should continue to enhance both endangered plant species that occur on the dunes (Oenothera deltoides ssp. howellii and Erysimum capitatum var. angustatum).
Maintain a genetically representative seed bank.
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