A new population of the caper-fruited tropidocarpum (Tropidocarpum capparideum) has been discovered in Vasco Hills Regional Preserve on protected land acquired by the East Bay Regional Park District (EBRPD) in partnership with the East Contra Costa County Habitat Conservancy (Conservancy). The plant had been undocumented for 68 years until a few individuals were observed on nearby private land in 2023.
“Our agencies are working together to conserve landscapes in eastern Contra Costa County that protect sensitive species while also providing recreation opportunities for the community,” said Park District General Manager Sabrina Landreth. “The discovery of this rare plant population illustrates the value of our partnership.”
A Storied Past
Botany professor Edward Lee Greene of the University of California, Berkeley, first discovered the caper-fruited tropidocarpum in 1888. At that time, Greene wrote that the species was “very common in the low alkaline valley lands skirting the San Joaquin River in Contra Costa County.”
The caper-fruited tropidocarpum is native to California and listed as 1B.1 (rare, threatened, or endangered in California and elsewhere) by the California Native Plant Society. While the species has been documented in multiple counties, its populations remain small. There are currently only two known populations in the East Bay.
Rediscovery
On March 3, 2025, botanist Heath Bartosh of Nomad Ecology, working on behalf of the Conservancy, was searching local ridgetops for caper-fruited tropidocarpum when he and his colleague Spencer Adams discovered the population.
“We have come a long way from the days when E.L. Greene said caper-fruited tropidocarpum was a common species,” said Heath Bartosh. “Since the late 1880s, non-native species have become more abundant, outcompeting native species. This find highlights how crucial public land conservation and stewardship are to native plants. Without the partnership of the Park District and the Conservancy, protection of this important native plant refugium would not be possible.”
“Caper-fruited tropidocarpum is an elusive species that we had hoped would be found on one our preserves. This inconspicuous plant has no shortage of suitable habitat on lands we’ve cooperatively preserved with the Park District.” noted East Contra Costa County Habitat Conservancy Executive Director Abigail Fateman. “Finding and documenting this new population required a thoughtful survey approach and persistence because annual plants may not germinate every year. This small population will be a high priority for monitoring and management for our team.”
Together, the Park District and the Conservancy have protected more than 14,000 acres of land in eastern Contra Costa County and continue to collaborate on conservation and management efforts to protect the new caper-fruited tropidocarpum population.
The East Bay Regional Park District is the largest regional park system in the nation, comprising 73 parks, 55 miles of shoreline, and over 1,330 miles of trails for hiking, biking, horseback riding, and environmental education. The Park District receives an estimated 30 million visits annually throughout Alameda and Contra Costa counties in the San Francisco Bay Area.