Rare Plant Program
The Rare, Threatened, and Endangered Plants of California
(from CNPS Inventory, 6th Edition, 2001)
The heart of the CNPS Inventory is our assessment of the current conservation status of each of our state's rare, threatened, and endangered plants. We present these assessments together with a summary of current information on the distribution and ecology of each taxon. We also include entries for plants that were considered but rejected for one or more reasons, as well as other scientific names that have been used in the standard literature or in previous editions of this Inventory.
Basis for Inclusion
The vast majority of the taxa in this Inventory are vascular plants (ferns, fern allies, gymnosperms, and flowering plants). With this edition, we for the first time also present our evaluation of rarity and endangerment of California's bryophytes (mosses, liverworts, and hornworts). Algae, fungi, and lichens are not treated here.
A plant must be native to California to be included. Ornamentals, plants escaped from cultivation, and naturalized plants are excluded. So are the sporadic hybrids that sometimes occur under natural conditions. The relatively trivial color variants and occasional departures from typical vegetative or floral conditions, referred to by botanists as "forma," are similarly excluded.
This Inventory focuses on plants that are rare in California. A very small number of plants that are still somewhat common in California are included because they are in decline and face further immediate threats. We recognize that extensive habitat alteration and pervasive human impacts pose serious threats to many other species that are still common. However, evaluation of threats to species that are neither rare nor imminently becoming so is outside the scope of this Inventory. By limiting our scope in this way, we in no way imply that these species are not of major concern.
The plants in this Inventory are presented alphabetically by their scientific names, the technical names that have been properly published for them according to the International Code of Botanical Nomenclature. See Shevock (1993) for a general discussion of nomenclature.
In its simplest form, a scientific name has three parts. The first is the genus or generic name. It is always capitalized. The second part is the specific epithet, often incorrectly called "the species name." Together, these two components make up the species name. If a scientific name is presented in its most complete form, these two words will be followed by the names of one or more persons, often in an abbreviated form, who first published the specific epithet or subsequently published a taxonomic modification of the plant. These names are the authorities. If a portion of an authority occurs within parentheses, then the author in parentheses originally placed the epithet in a different genus or species, or once assigned it to a different taxonomic rank. The name cited outside the parentheses is that of the person who published the combination as it now appears.
Often the scientific name is more complex because botanists have recognized categories below the level of species. The two most useful are the subspecies (abbreviated ssp.) and the variety (abbreviated var.) These names are also given according the International Code and they have their own authorities.
Consider the example Penstemon newberryi Gray var. sonomensis (Greene) Jeps. Penstemon is the genus or generic name; newberryi is the specific epithet; Gray, for Asa Gray, is the author of the specific epithet; var. is the abbreviation for variety; sonomensis is the subspecific epithet; (Greene), for Edward L. Greene, first described the var. sonomensis as a full species; and Jeps., for Willis Lynn Jepson, modified its taxonomic position and made it a variety of P. newberryi. Following the general practice for foreign words and phrases, Latin portions of the name (genus, species, and infraspecific epithet) are typically distinguished from surrounding text with underlining or italic typeface.
Each of the plants also has a common or vernacular name (except for the 28 nonvascular plants). We include these because it is often easier for many of us to refer to a plant by a more familiar sounding name. Of course, the majority of the plants in this book have no real common names. Most of them were coined by Leroy Abrams for his Illustrated Flora of the Pacific States. In other instances, we simply followed his lead by contriving names, usually by translating the Latin or Greek roots into English or by selecting an appropriate geographical reference or person's name. We have attempted to follow Kartesz and Thieret (1991) in matters of capitalization, spelling, and hyphenation of common names. Please see Appendix IV for an index between common and scientific names.
Each entry also includes the technical name of the family to which the plant belongs. Note that all of these names end with the suffix "-aceae." A few plant families have older, alternative names that the International Code allows to be used because their widespread acceptance predates formal nomenclature. Gramineae is a perfectly acceptable alternative for Poaceae; Compositae for Asteraceae; Cruciferae for Brassicaceae; Umbelliferae for Apiaceae; Leguminosae for Fabaceae; and Labiatae for Lamiaceae. However, these old names are gradually losing favor, so we have used the standardized, modern names for these families.
We use what we consider to be the current, best nomenclature based on the recommendations of RPSAC and consultation with taxonomic authorities. Many names in this Inventory have been in use for a long time, appearing in Munz (1959, 1968, 1974) and Abrams (1923-1960). Others have been introduced or reintroduced to us in The Jepson Manual (1993), or described new to science in the last several years.
The usage in this Inventory does not follow any single published source, though if other considerations are equal, we follow usage in the current list maintained by The Jepson Manual project. When the nomenclature we use varies from that of The Jepson Manual, we include information in the Notes section of each entry describing the situation. See Skinner and Ertter (1993) for a discussion of taxonomic coordination between the Inventory and The Jepson Manual.
Where there is disagreement among experts on taxonomic distinctiveness, we lean toward recognizing doubtfully distinct taxa. Such taxa are typically assigned to List 3. By encouraging protection until taxonomic questions are resolved, we hope to reduce ex post facto lamentation over taxa that have been shown to be distinct only after their disappearance.
We do not include taxa that lack formally published scientific names.
CNPS Ranking System -- The CNPS Inventory ranking system has been modified, and the R-E-D Code has been discontinued. This page contains an explanation of and rationale for these changes.
We have created five "lists" in an effort to categorize degrees of concern. They are described as follows:
List 1A: Plants Presumed Extinct in California
The 29 plants of List 1A are presumed extinct because they have not been seen or collected in the wild in California for many years. Although most of them are restricted to California, a few are found in other states as well. In many cases, repeated attempts have been made to rediscover these plants by visiting known historical locations. Even after such diligent searching, we are constrained against saying that they are extinct, since for most of them rediscovery remains a distinct possibility. Note that care should be taken to distinguish between "extinct" and "extirpated." A plant is extirpated if it has been locally eliminated, but it may be doing quite nicely elsewhere in its range.
We segregate these plants on their own list to highlight their plight and encourage field work to relocate extant populations. Since the publication of the fifth edition, eight plants thought to be extinct in California have been rediscovered. These are Ventura marsh milk-vetch (Astragalus pycnostachyus var. lanosissimus), San Fernando Valley spineflower (Chorizanthe parryi var. fernandina), diamond-petaled California poppy (Eschscholzia rhombipetala), Mojave tarplant (Hemizonia mohavensis), water howellia (Howellia aquatilis), Howell's montia (Montia howellii), northern adder's-tongue (Ophioglossum pusillum), and Shasta orthocarpus (Orthocarpus pachystachyus). One plant, frog's-bit buttercup (Ranunculus hydrocharioides), was inadvertently placed on List 1A in the fifth edition and is now correctly placed on List 2. Two plants that have not been seen recently have been moved onto List 1A: Santa Barbara morning-glory (Calystegia sepium ssp. binghamiae) and mesquite neststraw (Stylocline sonorensis).
All of the plants constituting List 1A meet the definitions of Sec. 1901, Chapter 10 (Native Plant Protection Act) or Secs. 2062 and 2067 (California Endangered Species Act) of the California Department of Fish and Game Code, and are eligible for state listing (see Conserving Plants with Laws and Programs..., above). Should these taxa be rediscovered, it is mandatory that they be fully considered during preparation of environmental documents relating to the California Environmental Quality Act (CEQA).
List 1B: Plants Rare, Threatened, or Endangered in California and Elsewhere
The 1021 plants of List 1B are rare throughout their range. All but a few are endemic to California. All of them are judged to be vulnerable under present circumstances or to have a high potential for becoming so because of their limited or vulnerable habitat, their low numbers of individuals per population (even though they may be wide ranging), or their limited number of populations. Most of the plants of List 1B have declined significantly over the last century.
All of the plants constituting List 1B meet the definitions of Sec. 1901, Chapter 10 (Native Plant Protection Act) or Secs. 2062 and 2067 (California Endangered Species Act) of the California Department of Fish and Game Code, and are eligible for state listing. It is mandatory that they be fully considered during preparation of environmental documents relating to CEQA.
List 2: Plants Rare, Threatened, or Endangered in California, But More Common Elsewhere
Except for being common beyond the boundaries of California, the 417 plants of List 2 would have appeared on List 1B. From the federal perspective, plants common in other states or countries are not eligible for consideration under the provisions of the Endangered Species Act. Until 1979, a similar policy was followed in California. However, after the passage of the Native Plant Protection Act, plants were considered for protection without regard to their distribution outside the state.
With List 2, we recognize the importance of protecting the geographic range of widespread species. In this way we protect the diversity of our own state's flora and help maintain evolutionary process and genetic diversity within species. All of the plants constituting List 2 meet the definitions of Sec. 1901, Chapter 10 (Native Plant Protection Act) or Secs. 2062 and 2067 (California Endangered Species Act) of the California Department of Fish and Game Code, and are eligible for state listing. It is mandatory that they be fully considered during preparation of environmental documents relating to CEQA.
List 3: Plants About Which We Need More Information - A Review List
The 52 plants that comprise List 3 are united by one common theme - we lack the necessary information to assign them to one of the other lists or to reject them. Nearly all of the plants remaining on List 3 are taxonomically problematic. For each List 3 plant we have provided the known information, indicated in the Note where assistance is needed, and tentatively assigned the taxon to a more definite list. Data regarding distribution, endangerment, ecology, and taxonomic validity will be gratefully received.
Some of the plants constituting List 3 meet the definitions of Sec. 1901, Chapter 10 (Native Plant Protection Act) or Secs. 2062 and 2067 (California Endangered Species Act) of the California Department of Fish and Game Code, and are eligible for state listing. We strongly recommend that List 3 plants be evaluated for consideration during preparation of environmental documents relating to CEQA.
List 4: Plants of Limited Distribution - A Watch List
The 554 plants in this category are of limited distribution or infrequent throughout a broader area in California, and their vulnerability or susceptibility to threat appears relatively low at this time. While we cannot call these plants "rare" from a statewide perspective, they are uncommon enough that their status should be monitored regularly. Should the degree of endangerment or rarity of a List 4 plant change, we will transfer it to a more appropriate list.
Very few of the plants constituting List 4 meet the definitions of Sec. 1901, Chapter 10 (Native Plant Protection Act) or Secs. 2062 and 2067 (California Endangered Species Act) of the California Department of Fish and Game Code, and few, if any, are eligible for state listing. Nevertheless, many of them are significant locally, and we strongly recommend that List 4 plants be evaluated for consideration during preparation of environmental documents relating to CEQA. This may be particularly appropriate for the type locality of a List 4 plant, for populations at the periphery of a species' range or in areas where the taxon is especially uncommon or has sustained heavy losses, or for populations exhibiting unusual morphology or occurring on unusual substrates.
CNPS R-E-D Code
With the five CNPS Lists we maintain a simple classification that reflects an overall level of conservation concern. However, rarity and endangerment are not strictly correlated, and our approach to protecting plants that occur only in California is somewhat different from our approach to protecting plants that also occur elsewhere. Developing effective conservation strategies requires that we distinguish among the separate factors that contribute to our List assignments. These are: rarity, which addresses numbers of individuals and distribution within California; endangerment, which addresses the plant's vulnerability to extinction for any reason; and distribution, which describes the overall range of the plant. Together these three elements form the R-E-D Code. Each element in the code is divided into three classes or degrees of concern, represented by the number 1, 2, or 3. In each case, higher numbers indicate greater concern. The system is summarized as follows:
R - Rarity
1 - Rare, but found in sufficient numbers and distributed widely enough that the potential for extinction is low at this time
2 - Distributed in a limited number of occurrences, occasionally more if each occurrence is small
3 - Distributed in one to several highly restricted occurrences, or present in such small numbers that it is seldom reported
E - Endangerment
1 - Not endangered
2 - Endangered in a portion of its range
3 - Endangered throughout its range
D - Distribution
1 - More or less widespread outside California
2 - Rare outside California
3 - Endemic to California
For example, an R-E-D Code of 3-3-3 indicates that the plant in question is limited to one population or several restricted ones, that it is endangered throughout its range, and that it is endemic to California. A summary of the R-E-D code system appears on the inside front cover for easy reference.
State and Federal Status
For each taxon with official status under the state and/or Federal endangered species acts, the plant's status is presented. Our definitions conform to those found in California state law and federal regulations, described elsewhere in this volume.
The distribution of the taxon is described by county or island within California, together with other states and countries where we know the plant to exist. We record only natural occurrences of rare plants, or occurrences that have been reestablished within the species' historic range as part of an approved recovery plan. For example, although both Northern California black walnut (Juglans hindsii) and Monterey pine (Pinus radiata) are widely planted within the state, we track only the few natural occurrences of these taxa. When we indicate that a particular plant occurs in a particular county, we are making a positive statement that is based upon specimens, photographs, the literature, or field observations. In no way does this imply that a plant does not occur in other counties in California or in other states. Our understanding of plant distribution constantly improves, and new localities for rare plants are frequently discovered, often in unpredicted circumstances.
We use the symbols "*" and "?" as modifiers, which respectively express extirpation and uncertainty. They are also are explained on the inside front cover for easy reference.
? uncertainty about distribution or identity
?* uncertainty about distribution, but extirpated if once present
(*?) occurrence confirmed, but possibly extirpated
To provide more detailed location information, we have also cited the U.S. Geological Survey (USGS) 7.5 minute quadrangle (quad) map for more than 1500 plants on CNPS Lists 1, 2, and 3. We employ a modified version of the quad numbering system previously used by the California Department of Water Resources. Please see Appendix I to translate this system's quad numbers into USGS topographic map names or vice versa. In those few cases where a quad is listed without a letter following the number, this indicates that our occurrence data are too vague to pinpoint its location on a 7.5 minute quadrangle. As with counties, this is positive siting information - when we indicate that a plant has been reported from an area on a topographic quad, it is based on hard data. In no way does this imply that a plant does not occur on a topographic quad we have not listed; rather, it may be there but botanists have yet to find it. As with distribution, quads are also often modified with the symbols "*" and "?", which respectively express extirpation and uncertainty (see above).
For each taxon, we present one or more habitats in which a rare, threatened, or endangered plant is typically found. This information is compiled from field survey forms, unpublished reports, original descriptions, floras, and herbarium material. Please refer to the printed or electronic versions of the 6th edition for more information on habitat types.
We present an elevational range for each taxon in meters. The stated range is for the California portion of a plant's range only (if the taxon also occurs outside the state). These elevational range data have been accumulated from literature, herbarium specimens, and field survey information.
We provide a brief description of plant duration and life form. The information was primarily developed from published and unpublished literature and from herbarium material. Our simplified classification system is as follows:
Duration: Annuals grow from seed and reproduce within a single year. Perennials live more than one year. Annual/Perennials are variable depending on environment and conditions.
Growth Form: Herbs are herbaceous and lack above-ground woody tissue. bulbiferous herbs have fleshy underground storage organs typically derived from scale leaves (this category includes cormiferous and other similar plants in which storage organs have other origins). rhizomatous herbs have underground stems (rhizomes), typically bearing shoots which develop into new plants. stoloniferous herbs have above-ground runners (stolons) which typically root and produce new plants.
Shrubs are smaller woody perennials that retain most of their above-ground woody tissue and are typically many-stemmed. leaf succulents have thick, fleshy leaves. stem succulents have thick, fleshy stems and reduced or absent leaves.
Trees are larger woody perennials that retain all of their above-ground wood tissue and are typically single-stemmed.
Vines are twining woody perennials requiring external support for growth.
Mosses are small green plants (one of three groups of bryophytes) with structures that resemble miniature leaves and stems. The leaves generally have a midrib called a costa. The sporophyte (the spore-bearing structure) is persistent for weeks.
Liverworts are small green plants (one of three groups of bryophytes). There are both leafy and thalloid types - leafy liverworts lack a midrib on the leaves, while thalloid liverworts have no leaves. The sporophyte is short-lived.
Leaf Condition (for shrubs, trees, vines only): Deciduous plants shed their leaves for part of the year. Evergreen plants retain their leaves for an entire year.
Special Habitat: Aquatic plants are submerged or floating on the water surface. Emergent plants are rooted in water but bear some foliage out of the water.
Mode of Nutrition: Achlorophyllous plants lack chlorophyll and live on existing organic matter in the soil. Hemiparasitic plants are connected to host plants and derive energy, water, and minerals from them, but also maintain their own functional root systems or photosynthetic surfaces. Parasitic plants are connected to host plants and rely solely on them for energy, water, and nutritional requirements. Carnivorous plants trap insects and other small animals and derive nourishment from them.
As in most classifications, some of the above distinctions are somewhat arbitrary, particularly the divisions between growth forms. Furthermore, plant growth form can vary depending on geography and local environmental conditions. Perennials that are often referred to as either suffrutescent herbs or subshrubs present special difficulties. Generally, if these plants die back seasonally to the ground or to a small crown of woody tissue we classified them as herbs, and if they retain much or all of their woody above-ground tissue we called them shrubs.
We show the months when each rare plant is typically in bloom. For ferns and other spore-bearing plants, we have given the months when spores are released and spore-bearing structures such as sori are typically present on the plant. We have not included any comparable information for gymnosperms and nonvascular taxa.
Many entries include additional notes on distribution, endangerment, relationship to names in The Jepson Manual, or important literature citations. We have again included information about legal status and endangerment in neighboring states in the notes; official state designations are specifically indicated as such and capitalized, as in "State-listed as Endangered in OR". We have made a special effort to indicate missing information about distribution, endangerment, or taxonomy for each entry, in the hope that knowledgeable users will fill in the gaps. Abbreviations that are commonly used in the notes are explained on the inside front cover.
Abrams, L.R. 1923?1960. An Illustrated Flora of the Pacific States, Washington, Oregon and California. Vol. 4 by R. Ferris. Stanford University Press. Stanford, CA. 4 vols.
Hickman, J.C., ed. 1993. The Jepson Manual: Higher Plants of California. University of California Press. Berkeley, CA. 1400 pp.
Holland, R.F. 1986. Preliminary Descriptions of the Terrestrial Natural Communities of California. Nongame-Heritage Program, California Department of Fish and Game. Sacramento, CA. 156 pp.
Kartesz, J.T., and J.W. Thieret. 1991. Common names for vascular plants: Guidelines for use and application. Sida 14(3):421-434.
Munz, P.A. 1959. A California Flora. In collaboration with D.D. Keck. University of California Press. Berkeley, CA. 1681 pp.
Munz, P.A. 1968. Supplement to a California Flora. University of California Press. Berkeley, CA. 224 pp.
Munz, P.A. 1974. A Flora of Southern California. University of California Press. Berkeley, CA. 1086 pp.
Shevock, James R. 1993. How plants get their names and why names change. Fremontia 21(1):19-24.
Skinner, Mark W. and Barbara Ertter. 1993. Whither rare plants in The Jepson Manual? Fremontia 21(3):23-27.