Illustration from Abrams (1960)
Photo taken at Twin Lakes State Park © 2007 by Dylan Neubauer
Photo by Kevin Merk
Photo taken at Twin Lakes State Park by Dylan Neubauer
Holocarpha macradenia distribution map
This fact sheet was prepared by Grey F. Hayes and Dean W. Taylor under award NA04N0S4200074 from the National Oceanic and Atmospheric Administration (NOAA), U.S. Department of Commerce (DOC). The statements, findings, conclusions, and recommendations are those of the authors and do not necessarily reflect the views of the NOAA or the DOC.
© Copyright 2006, Elkhorn Slough Coastal Training Program
Last updated: Sep 6, 2007 21:53
Coastal prairie on marine terraces flanking the northern Monterey Bay (and, formerly, around the outer San Francisco Bay)
Annual herb from a basal rosette of leaves, rosette and basal leaves withered at flowering, rosette and lower cauline leaves with small marginal teeth, 2–10 cm long and approximately 8 mm wide across the blade; the leaves on the stems progressively become linear and bract-like; plants strongly scented and densely glandular, with axillary leaf clusters tipped by tack-shaped yellow glands exuding “tar”-like compounds. Larger plants branched; flower heads clustered and spherical, 10–14 mm diameter, with 5–8 mm long phyllaries; 8–16 ray flowers with 4–6 mm long ligules; many more (40–90) disk flowers, which have black anthers. Superficially similar to much more common coast tarweed (Deinandra corymbosa ssp. corymbosa), which has deeply lobed leaves and is more frequently seen in the same coastal prairie habitat.
June to November
City of Santa Cruz Arana Gulch Greenbelt; Elkhorn Slough Foundation’s Porter Ranch
Extant only in central California in Monterey and Santa Cruz counties. Extirpated from Alameda, Marin, and Sonoma Counties; found in Contra Costa County only in introduced populations on East Bay Regional Parks property.
Remaining natural populations in the San Francisco Bay area were extirpated in 1990s and persist there only as artificially seeded occurrences in Wildcat Canyon Regional Park (Havlik 1987). Since the 1970s, several populations have become extirpated in Santa Cruz County (Palmer 1987) and most others have declined significantly.
The species is known to tolerate grazing and to decline in pastures where grazing is discontinued, allowing weedy exotics to create a tall overstory that inhibits growth of the lower statured tarplant and other low herbs (Hayes and Holl 2002). Several populations have had high numbers when grazed and suffered drastic declines after the cessation of grazing. A population at the Watsonville Airport, with a mowing regime that simulates grazing, has supported between 400,000 to as many as 27 million plants, fluctuating in relation to rainfall; the site is vulnerable to development.
Abrams, L. 1960. Illustrated Flora of the Pacific States. Stanford University Press, Palo Alto, CA.
Havlik, N. The Santa Cruz tarplant relocation project, pp. 421–425 in T. S. Elias, ed., Conservation and Management of Rare and Endangered Plants. California Native Plant Society Press, Sacramento, CA.
Hayes, G. and K. D. Holl. 2002. Cattle grazing impacts on annual forbs and vegetation composition of mesic grasslands in California. Conservation Biology 17(6):1694–1702.
Palmer, R. 1987. Evolutionary relationships of Holocarpha macradenia, pp. 425–431 in T. S. Elias, ed., Conservation and Management of Rare and Endangered Plants, California Native Plant Society Press, Sacramento, CA.