Rare Plants of San Diego County--Introduction

San Diego County's rapidly diminishing native vegetation includes an extraordinary number of rare or uncommon plant species. Geologic variability and unusual edaphic factors account for much of this diversity which is bolstered by relictual Sierran elements found in the mountains, typical Baja species with ranges extending north of the border, and a wide array of plants in the Anza-Borrego Desert. This present work attempts to compile as much available site information as possible for several hundred species which are generally considered sensitive by local, state, and federal agencies.

A wide variety of resources were utilized and information has been compiled in a cumulative fashion over several decades. During this period the following biologists have graciously provided significant information concerning their own field experiences: Ellen Bauder, Mitch Beauchamp, Ellen Berryman, Roxanne Bittman, Stephen Boyd, David Bramlet, John Brown, Tim Cass, Duffie Clemons, Vince Coleman, Mike Curto, Jim Dice, Richard Felger, Judy Gibson, Patricia Gordon-Reedy, Dylan Hannon, Bonnie Hendricks, Larry Hendrickson, Kyle Ince, Eric Jonsson, Robin Knehr, Dawn Lawson, Geoff Levin, Eric Lichtwardt, Maggie Loy, Karlin Marsh, David Mayer, Reid Moran, Tom Oberbauer, Alaina Reiser, Fred Roberts, Andrew Sanders, Mark Skinner, Fred Sproul, Colin Steele, Janet Stuckrath, Larry Sward, Gilbert Voss, Peter Warren, Carl Wishner, Julie Vanderwier, Howie Wier, and Rick York.

These invaluable recollections have been supplemented by the author's extensive botanical field work in Southern California (1975-1994). The latter includes site visits and follow-up biological survey reports (primarily from 1987-1994 as a biological consultant) for approximately 400 separate locales covering well over 300,000 acres in this region. These reports were typically prepared for California Environmental Quality Act (CEQA) documentation. Field work, performed at various seasons, generally required a floristic census of the site as part of the standard report methodology. Rare plant searches were a focus of such field censuses. Included here was a comprehensive botanical survey over a three year period of 125,000 acre Camp Joseph Pendleton in northwestern San Diego County; as well as extensive field work conducted on the 23,000 acre Otay Ranch near the Mexican border. A vegetation community mapping project for approximately 1.3 million acres of western Riverside County also included substantial field work and yielded information about range extensions into that region. Most large tracts of land in coastal portions of San Diego County were sampled during various surveys. Unfortunately, this strongly correlates with proposed development and underscores the trend towards massive losses of native habitat and consequent losses of sensitive plant populations. Also compiled over the last two decades was a photographic flora covering most of the 1500 native plant species and almost all of the CNPS designated sensitive plant species for the County which are discussed within this work.

Also utilized were numerous historical site reports compiled by various other biologists, the California Natural Diversity Data Base, and the herbarium at the San Diego Natural History Museum. The last mentioned was regularly scoured for significant details regarding rare plant information. An attempt was made to weed out spurious reports and misidentified herbarium specimens which might skew an objective assessment of a species' current status. Some plants have ranges strongly correlating with areas now urbanized, and an effort was made to comment upon clusters of historical sightings which might represent locales where the native vegetation is no longer extant.

Organization of this work has several parameters necessitating discussion. All sites mentioned have been visited by the author, except those specifically prefaced with a term denoting that a rare plant population was not seen. Hence, all "reported" sites have been culled from other sources which are presumed to be accurate, but which were not independently verified. While this general methodology can result in the redundant use of several terms, this was considered the most pragmatic way to clearly separate out rare plant sites discovered or re-examined by the author and presumed extant, and those reports which may have inherent problems (e.g., extirpated sites which have long since ceased to harbor sensitive plants, sites which may represent misidentifications based on outdated taxonomic keys, or reports which may contain erroneous or overgeneralized locality information). "Herbarium" specimens invariably refer to pressed plants kept in the collection at the San Diego Natural History Museum, which were examined at that facility. Unfortunately, time constraints would not allow me to site specific collection numbers; other than to note for purposes of range information, southernmost collections from Baja California.

An additional reason for some redundancy was to consistently maintain comparative assessment terms from one species discussion to the next; particularly under the "Status" section. "Stable" implies that population numbers overall are static or may be slowly diminishing, but for which the overall vigor of the cumulative populations is not immediately threatened. "Presumed stable" is regularly used for species in mountain, desert, or transmontane areas with limited ongoing development, for which little new data is available, but for which such an assessment may be inferred. "Declining" implies that a noticeable and significant reduction in numbers is evident, and for which the perceived reduction is apparently a trend which cannot bode well for the future of this species in San Diego County. "Severely declining" constitutes a red flag which will require proactive remedies to counter. A handful of other (hopefully self-explanatory) adverbs are utilized as variants. "Unknown" indicates there is a dearth of information on the status of this species in San Diego County, and a more subjective assessment would not be productive. As a general rule it should be stated that information for species with predominantly coastal ranges, far exceeds what is available for montane and desert species. Hopefully this work will focus attention on specific plant taxa which warrant substantially more field research.

Plants are arranged alphabetically by scientific name, but include the common name given by the CNPS to these often uncommon species. Natural Diversity Data Base information is current as of the February 1994 CNPS Inventory. It is recognized that state and federal listings will invariably change as more information is gathered. Future plans call for an "electronic" system in which an updated plant status can be accessed or altered within the State database system at any time. This avoids the cumbersome annual or semi-annual updates of the past, but ironically, it implies data may be outdated immediately after it is accessed. Such a system will readily antiquate listing information presented in this work, and readers are urged to stay abreast of such changes via communications with the Sacramento database.

Soils information is cursorily taken from the U.S. Soil Conservation Service's 1973 work covering San Diego County. No attempt was made to comprehensively research all locales, only to choose typical sites and supply some initial soil information. Future versions of the current work should attempt to refine the soils analysis by listing prevalent versus secondary soil types utilized by specific rare plant species. County range maps and possible color plates illustrating many of the rare plants in flower are proposed for such a future version.

An attempt was made to provisionally summarize the status of San Diego County's rare plants in Baja California (within a paragraph separated from the general site information). This information relies primarily on a number of herbarium specimens collected at the San Diego Natural History Museum (fewer total collection numbers typically indicating greater rarity); as well as a latitude for the southernmost locale represented. The incomparable Reid Moran has field collected the majority of these specimens. Forays by the author into northern Baja California are appended to this information. It should be understood that vast areas of Baja California have only been surficially examined by botanists. The goal of this added information is to indicate which San Diego County plant species may also be extremely rare in Mexico, not to designate which "sensitive" species can be disregarded in the U.S. because they are more common elsewhere. Development of northern Baja California is already preceding along the lines of Southern California in earlier parts of this century, with widespread destruction of habitat for agriculture and orchards, and substantial beach bluff residential development. Given similar development pressures, species greatly reduced in historical numbers in the U.S. may decline for similar reasons in Baja California. In some cases, particularly in regard to beach dune habitat, this is already happening.

Despite some obvious shortcomings, it is hoped this work will provide some needed refinement to assessing specific sensitive plant resources in the region. I would like to urge readers to submit to me any atypical rare plant sightings not listed within this work, or sightings of obscure and rarely collected County species not listed within this document, for possible inclusion within a future updated version of this report.... Adios.

Craig Reiser

April 1994


Copyright May 1994 Craig H. Reiser.

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