Rare, Unusual and Significant Plants

Rare, Unusual and Significant Plants of Alameda and Contra Costa Counties

Eighth Edition, 2010

We are pleased to report that the eighth edition of Rare, Unusual and Significant Plants of Alameda and Contra Costa Counties is now available. First published in 1992, this report contains a wealth of information on both statewide and locally rare native plant species of the East Bay, ranking them according to their rarity and endangerment at the local level. It has received wide praise for providing invaluable information to land planners and managers, conservationists, consultants, teachers, students, researchers, professional and amateur botanists, and the general public.

This is the only publication addressing the locally rare native plant species of Alameda and Contra Costa Counties that are covered under the California Environmental Quality Act (CEQA), as well as the federally and state protected rare species occurring in the two counties. Watch Lists are also included of other native plant species that could become rare, threatened or endangered locally if various detrimental conditions persist.

Many changes have occurred in the East Bay’s vegetation since the last edition of this report in 2004 and several new appendices have been added to help track those changes, including one listing the plant species that have had rank changes since the last edition.

New species have been added to the report and some have been deleted. New locations have been found for some species, while other species have disappeared from some locations and have thus become rarer.

A map of 29 botanical hot spots in the East Bay is included, and an appendix of nomenclature changes has been added.

Many other updates and changes are included in the report and this new edition is sure to once again prove to be a valuable and important asset for both professionals and amateurs alike, providing extensive data for land planning, conservation, and management; for plant study; and for native plant enjoyment in general.

Dianne Lake

Unusual Plants Co-Ordinator

Click here for a pdf order form for the Eight Edition of Rare Unusual and Sgnificant Plants of Alameda and Contra Costa Counties.


The eighth edition of Dianne Lake's Rare, Unusual and Significant Plants of Alameda and Contra Costa Counties is now available. The database of over 19,000 records that is the basis for the eighth edition will soon be available on the web, through The Calflora Database. (The database for the earlier editions is already on line.) Each observation from the EB Unusual Plants database includes the taxon, observer, and date. For rare taxa, the East Bay region code (from the map in Dianne’s book) is listed. For taxa that are more common in the East Bay and elsewhere, a great deal of detail is included about each observation’s location–much more than could be included in the printed edition of the book.

The Calflora Map Viewer now includes the regions from the EB Rare and Unusual Plants database; if a plant occurs in on of these regions, it is drawn in color on a relief map, alongside observations at specific points (shown as dots) and “quads” from the state CNPS Inventory, and the many other Calflora sources of observations. For more information about the Map Viewer, visit the Calflora web site and click the Map Viewer link on the front page or in any sidebar.

The printed book of course remains the official source of the EB Rare and Unusual Plants data and continues to be available from Dianne Lake.


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Seventh Edition

Table of Contents

Definition of Unusual Plants
Importance of Unusual Plants
Legal Implications and Protection for Unusual Plants
Report: Rare, Unusual and Significant Plant of Alameda and Contra Costa Counties
Location System for Unusual Plants: Regions and Specific Sites
Ranking System for Unusual Plants
How You Can Help
A1 Species Location Table
A2 Species List
A1x List (Species Presumed Extirpated)
A1? List (Questionable Species)
Unusual Plants Survey Form
Rare, Unusual and Significant Plants of Alameda and Contra Costa County order form

Definition of Unusual Plants

The East Bay has a wealth of native plant species but many occur in only a few places here even though they may be more common in other parts of California.

Alameda and Contra Costa Counties act as a botanical melting pot where many native species reach their range limit in one of the two counties and many others occur in habitats that are very limited, isolated, or threatened here. Still others are in severe decline due to habitat loss, weed and insect invasions, changes in land use, altered water courses, or other detrimental factors.

The East Bay Chapter of CNPS has designated these species that are rare or threatened locally but possibly more common elsewhere in the state as “Unusual Plants.” Many years of surveying, monitoring and research by many dedicated CNPS volunteers have gone into determining which plants of our local native flora qualify as unusual plants.

Over the years, criteria were developed and a ranking system was devised to denote the degree of rarity and endangerment of these unusual plants in Alameda and Contra Costa Counties.  A database was set up to track these plants and surveying, monitoring, and other research activities continue every year so that we can constantly reassess and update the status of these plants in our two-county area.

In 1991 a report was published, Unusual and Significant Plants of Alameda and Contra Costa Counties, providing the results of this constant monitoring and research. The report is updated periodically (currently in its seventh edition) and it quickly became an important tool for botanists, land managers, planners, researchers, consultants, conservationists, etc. in their work around the East Bay. (The report is available at a cost of $20 and an order form is provided below.)

Importance of Unusual Plants

In many instances our unusual plant species are even rarer and more threatened locally than several of the statewide rare plants that occur in the East Bay. The preservation of these locally rare populations is important for a multitude of reasons.

Isolated and range limit, or peripheral, populations have often been found to possess plants with greater genetic variation and better survival rates than those in populations occurring where the species is more common. In rapid and catastrophic extinctions of large populations, the plants on the periphery of a range or in isolated disjunct populations have often survived. Common species with large populations can often disappear rapidly in the face of a catastrophic event or a pathogen moving from plant to plant, but isolated populations can often escape this fate simply due to their distance from the main populations. Conditions at the range edges of a species or in isolated populations are often more hostile and plants there tend to develop stronger survival mechanisms. These isolated and peripheral populations can sometimes be the only hope for survival that a species has in the event of an environmental disaster, and thus it is essential to identify where these populations exist and to take the necessary steps to ensure their survival.

Several of our unusual plants occur in habitats that are limited or threatened statewide as well as in the East Bay, such as vernal pools, alkali sinks, serpentine environments, and miscellaneous wetlands and riparian areas. Because these habitats are so limited, many of the species that occur in them are also rare or threatened. Many of the unusual plants in the East Bay occur only in these limited or threatened habitats, although some can also be found in other types of habitats and are thus less vulnerable. By identifying the rare and unusual plants found in these local places, these declining or limited habitats can be identified and protected.

Clusters or suites of rare and unusual plants are sometimes found and these “botanical hotspots” usually indicate special environmental conditions such as unique soils, water patterns, limited pollinators, or other factors that contribute to our local biological heritage and diversity and that need to be preserved. Studying the plants and conditions in these areas can also help us better understand what various rare plants need to survive and to define patterns and trends that may cause local rarity. Some of the “botanical hotspots” of the East Bay are Mt. Diablo State Park, Antioch Dunes National Wildlife Refuge, Flicker Ridge, Black Diamond Mines Regional Preserve, Lime Ridge, Byron Hot Springs, Corral Hollow, Springtown Wetlands Preserve, Sunol and Ohlone Regional Wildernesses, Don Edwards National Wildlife Refuge (Warm Springs section), Redwood Regional Park, and the Mines Rd. area south of Livermore.

It is important to recognize that plants and their habitats are interdependent and when species are found to be in rapid decline in an area it is an indication that the natural resources and biodiversity of that area are in trouble. Studying and becoming aware of our local unusual plants is not just about preserving individual species but is also a way to determine local botanical areas of native plant diversity, define places with threatened habitats or suites of endangered plants, define patterns and trends that cause local rarity, and identify areas in need of study or conservation that may have other special environmental factors.

Legal Implications and Protection for Unusual Plants

When several locally rare species occur on a property, even if there are no statewide rare plants there, it should be considered a significant impact under guidelines in the California Environmental Quality Act (CEQA) that refer to locally rare populations in sections 15380 and 15125a which address species of local concern and place special emphasis on environmental resources that are rare or unique to a region.

CNPS and other organizations and individuals have been instrumental in alerting local land planners and managers about the existence and importance of these unusual plants during public review periods for EIRs and other land planning documents.

CNPS has also notified the cities and agencies of Alameda and Contra Costa Counties  about the rare and unusual plants known to occur in each of their areas. A list of CEQA-protected species for their area has been provided to every city and agency along with a letter explaining the importance of these species, their legal protection, and the need to consider these species in any land use activities or changes in their area.

Report: Rare, Unusual and Significant Plants of Alameda and Contra Costa Counties

A database was set up for the unusual plants of the East Bay in the late 1980’s and a report entitled Unusual and Significant Plants of Alameda and Contra Costa Counties was compiled and published in 1991 by the East Bay chapter to identify and assess the unusual plants of the two counties and to help botanists, land managers, planners, researchers, conservationists, etc. become aware of the importance and vulnerability of these local species and the need to protect them. The report is updated periodically and is currently in its seventh edition (March 2004).

Although it originally addressed only the locally rare plants, the report now includes the statewide rare plants that occur here and has been renamed Rare, Unusual and Significant Plants of Alameda and Contra Costa Counties.

Providing rank, locations and habitat for each species, the report is widely used and has become an important tool in conservation and planning efforts in the two counties.

Location data is provided in the report in general terms to protect against vandalism and indiscriminate collecting that has unfortunately occurred in the past, but more detailed location data is kept in the supporting database and is available upon request by contacting Dianne Lake at diannelake@yahoo.com  and explaining the need for specific data and how it will be used. Specific location information will be provided when available and if appropriate.

A new edition will be available in March 2010.

Location System for Unusual Plants: Regions and Specific Sites

In the report and its supporting database, a location system is used of regions and locations rather than of individual occurrences because of the difficulty of comparing many historical records for the area to current sites. Records from the late nineteenth and early twentieth centuries often merely describe a site as “Berkeley Hills” or “Oakland”, for example, and provide no further detail. Thus, when sites or multiple sites for a plant species are now found in these areas, it is usually impossible to determine if any of those sites correspond to the historical site or if there were more or possibly even less populations of that particular species there in the past. For this reason, specific site details are now always requested and are of the utmost importance when reporting population locations (although this specific location data is usually not made available to the general public because of past incidents of vandalism, over-collecting, etc. as described in the previous section).

A system was therefore devised of locations and eventually regions composed of those locations. The two counties were analyzed according to vegetation, geology, habitats, soil types, and other factors and were divided into 40 botanical regions. Rank is based on how many regions a species occurs in and then how many locations within that region. In most cases, plants occurring in five or fewer regions (A-ranked plants) also have very few locations within those regions. In a few cases, however, plants occurring in only a few regions have several locations within some of those regions and thus can be given a lower rank.

Ranking System For Unusual Plants

The database set up by the East Bay Chapter to track the rare and unusual plants of the East Bay currently consists of 16,429 records for 1,049 native plant species. Of these, 719 species (including 117 statewide rare plants that are known from the two-county area) are A-ranked by the East Bay Chapter, indicating that they are known from only five or fewer regions of the East Bay or are otherwise endangered here. These A-ranked species are required for consideration under CEQA guidelines in Sections 15380 and 15125(a) when they occur in areas where development or land use changes are proposed.

These A-ranked species are broken down into several ranks:

*A1x, *A1 or *A2:  Species in Alameda and Contra Costa counties listed as rare, threatened or endangered statewide by federal or state agencies or by the state level of CNPS.

A1x: Species previously known from Alameda or Contra Costa Counties, but now believed to have been extirpated, and no longer occurring here.

A1:  Species currently known from 2 or less regions in Alameda and Contra Costa Counties.

A2:  Species currently known from 3 to 5 regions in the two counties, or, if more, meeting other important criteria such as small populations, stressed or declining populations, small geographical range, limited or threatened habitat, etc.

A?:  Species that have been reported in the two-county area but identification is questionable and the species may not actually occur here.

In addition to the A-ranked species, a two-tiered Watch List of B and C ranked plants tracks local native species that are not currently considered rare or endangered in the East Bay but that could become so if certain conditions persist such as over-development, water diversions, excessive grazing, weed or insect invasions, etc. B ranked species occur in 6 to 9 regions in the two counties or are otherwise subject to threat, and C ranked species occur in 10 or more regions here but have potential threats.

How You Can Help

The continued monitoring, tracking and preservation of our local native flora is dependent on the efforts of our many CNPS volunteers and others who provide data on the rare and unusual plants they find while working and hiking in the East Bay.

A table and three lists are provided for the East Bay’s A-ranked species which are protected under CEQA. Clink on the links to obtain the documents in pdf form.

A1 Species Location Table: This table is of A1-ranked plant species which are those that occur in only two or fewer regions of the East Bay either currently or historically. These are the rarest of the rare and unusual plants of Alameda and Contra Costa Counties and thus the most in need of protection and monitoring in our area. The table includes locations, habitats, and the date the plant was last seen at each site. In some cases this date may be as long ago as the 1800’s or early 1900’s, or it may be as recent as this year.

A2 Species List: A list of A2-ranked species follows the A1 location table. These are plants that occur in only three to five regions of the East Bay either currently or historically. They are not currently included in a location table because of the time involved in compiling such a table but since these species are also required for consideration under CEQA, a list of them is provided consisting of species names and habitats.

A1x List (Species Presumed Extirpated): This is a list of plants that have not been reported since 1975 or before in the East Bay and are presumed to no longer occur here. This list previously appeared on the website but it has now been updated and habitats have been added. Although these species are included in the A1 table, a separate list is also provided to help focus field efforts and to emphasize how many species have disappeared from our area.

In the past year two of the species on the former list were rediscovered in the East Bay  thanks to the diligent efforts of CNPS volunteers and others. Heterodraba unilateralis was found in the Corral Hollow area southeast of Livermore and Meconella californica was found in Pleasanton Ridge Regional Park. More populations of presumed extirpated plants may be out there just waiting to be rediscovered in areas that have not been surveyed for a very long time. There is always hope that populations that were thought to be lost will be found if we just look hard enough.

A1? List (Questionable Species): This is a list of species that are of questionable identification and further research is needed to determine whether or not they actually occur in the two-county area. Since this is a relatively short list, locations are included so that volunteers can know where to focus their surveys to further study these plants.

Please review the table and lists above. If you encounter any of these species in our two counties this year or if you have any recent information on them in our area, especially those species that have not been reported here in the last ten years or more, please fill out the Unusual Plant form and send it with a map of where the plant was found to Dianne Lake, 1050 Bayview Farm Rd, #121, Pinole, CA 94564. Or, if a map or other data are not available, please at least send an email to diannelake@yahoo.com with the location (as specific as possible, including GPS coordinates if available), number of plants, condition of population, and date observed.

Your help is greatly appreciated and needed to keep our knowledge of our rare and threatened plants up to date. Together we can continue to monitor and protect the rarest of the rare of our East Bay native flora.

Dianne Lake
Unusual Plants Coordinator
diannelake@yahoo.com

The following was added on April 1, 2009:

Every year several of us comb the hills and dales of Alameda and Contra Counties tracking our “unusual” plants. These are plant species that are locally rare, but not necessarily rare around the rest of the state. Several of these plants have even fewer populations in our area than the statewide rare species that occur here.

I would like to put out a plea to all of our members this year to help with this endeavor and to keep an eye out for these “unusual” plants as you hike and botanize around our two counties. Following are some of the priority plants and tasks that we need help with.

1) The following plants have not been reported for quite some time and may no longer occur here. If anyone finds a population of any of these plants in either Alameda or Contra Costa County, please record specific location data (GPS points, a map, and/or precise written directions) and the size and condition of the population, and let me know immediately (see contact information below). Be sure the identification is correct – either have it verified by an expert (e.g. contact the Jepson Herbarium at UC Berkeley, 510-642-2465) or be able to back up your identification:
Amsinckia eastwoodiae
Astragalus didymocarpus
ssp. violaceum (other than the Los Mochos and Mt. Diablo sites)
Carex heteroneura
Crassula solieri
Cuscuta californica var. breviflora and
var. californica
Eriophyllum wallacei
Mimulus androsaceus
Mimulus floribundus
Mimulus tricolor
Ranunculus orthorhynchus
var. bloomeri
Piperia (any in Pt. Molate area)

2) The plants listed in the two tables occur at one or more sites in our two counties but more specific location data and/or identification verification is needed for only some of those populations, as follows. The first table lists kmown locations of interest. The second lists known plants but asks about varieties or subspecies.If anyone finds any of these populations, please carefully record the location details and the condition of the population and habitat and contact me at diannelake@yahoo.com so I can send you an Unusual Plant Survey Form to fill out.

Also contact me if you would like more information for any of these populations, or if there is a particular species or location you would like to research, or if you would like to know if there are other plants in need of research in a specific area or at your favorite hiking spot. More information on the Unusual Plants project is also available on our Chapter website at http://www.ebcnps.org/plantscience.html.

Thank you ahead of time to all who are able to help.

Dianne Lake
Unusual Plants Chair
diannelake@yahoo.com