Table of Contents
OCCURRENCE DATA FROM THE CNDDB*
Element Occurrence Ranks*
Historical >20 Years:
Recent <=20 Years:
The mission of the CNPS Rare Plant Program is to develop best available scientific information on the distribution, ecology, and conservation status of California’s rare and endangered plants, and to use this information to promote science-based plant conservation in California. One of the ways we fulfill our mission is by providing open access to the continuously updated, online CNPS Inventory of Rare and Endangered Plants of California. The heart of the CNPS Inventory is our assessment of the current conservation status of our state's rare, threatened, and endangered plants. We present these assessments together with a summary of the distribution and ecology of each taxon. We also include entries for plants that were considered but rejected (CBR) for one or more reasons, as well as other scientific names and synonyms that have been previously used in this Inventory.
The Inventory is intended to provide guidance for rare plant education, protection, conservation planning, and land acquisition and management in California. Prior to being made available online in 2001, CNPS published six print editions of the CNPS Inventory from 1974 to 2001. These previous editions are freely available to download on our website here.
The vast majority of the taxa in this Inventory are vascular plants (ferns, fern allies, gymnosperms, and flowering plants). We also present our evaluation of rarity and endangerment of California's non-vascular plants (mosses, liverworts, and hornworts) and lichens. Algae and fungi are not treated.
A plant must be native to California to be included. Ornamentals, plants escaped from cultivation, waifs, and naturalized plants are excluded. So are the sporadic hybrids that sometimes occur under natural conditions. Plants with the rank of forma, representing relatively trivial color variants and occasional departures from typical vegetative or floral conditions, are similarly excluded.
This Inventory focuses on plants that are rare in California. A small number of plants that are still somewhat common in California are included because they are evidently in decline and face further immediate threats. We recognize that climate change, 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 convention, the scientific name of a species, subspecies or variety is always in Latin (or treated as such), and each taxon has only one correct name. However, these names are subject to change, for example in cases of misidentification or application of the principle of priority (i.e., if literature research reveals an older name than the one in current use). Most name changes are the result of a change in classification, for example if a species is treated as a synonym of another species or placed in a different genus, or if new information indicates that a plant previously treated as a subspecies should be recognized at the rank of species.
CNPS uses the best available scientific nomenclature based on the recommendations of the Rare Plant Program Committee 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 in the Jepson eFlora (Jepson Flora Project 2021) or recently described as new to science.
The usage in this Inventory does not follow any single published source, though in most cases we use the names found in the Jepson eFlora. When the name we use differs from that of the Jepson eFlora, we conduct research and develop a status review to determine whether it is the best and most current nomenclature to follow. 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 towards recognizing doubtfully distinct taxa. Such taxa are typically assigned to California Rare Plant Rank 3. By encouraging protection until taxonomic questions are resolved, we hope to reduce ex post facto regret over taxa that have been shown to be distinct only after their disappearance.
We do not include taxa that lack formally published scientific names or names that do not conform to the rules and recommendations in the International Code.
This field includes the full scientific name of a species, subspecies, or variety, including the authors who published that name.
The plants in this Inventory are presented by their scientific names that have been effectively and validly published according to the International Code of Nomenclature for algae, fungi, and plants (Turland et al. 2018). See Shevock (1993) for a general discussion of nomenclature.
In simplest form, a scientific name has three parts. The first is the name of the genus and is always capitalized. The second part is the specific epithet. Together, these two components make up the binomial or “species name.” In its most complete form, a scientific name is presented as a binomial 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 is placed within parentheses, then this means that the author in parentheses originally placed the taxon in a different genus or species, or once assigned it to a different taxonomic rank. The authority cited outside the parentheses is the person who published the combination as it now appears.
Often the scientific name is more complex because botanists have formally recognized categories below the rank of species. The two most useful infraspecific ranks are the subspecies (abbreviated ssp. or subsp.) and the variety (abbreviated var.). These names are also displayed according to the International Code, and they have their own authorities.
Consider the example of Penstemon newberry Gray var. sonomensis (Greene) Jeps. Penstemon is the generic name; newberryi is the specific epithet; Gray, short for Asa Gray, was 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 Linn Jepson, modified its taxonomic position and made it a variety of P. newberryi. Following general practice, the Latin portions of the name (genus, species, and infraspecific epithet) are distinguished from surrounding text with underlining or italic typeface.
Each of the plants has a common or vernacular name. We include these because it is often easier to refer to a plant by a more familiar-sounding name. Most of the common names were coined by Leroy Abrams for his Illustrated Flora of the Pacific States. In other instances, we simply follow 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 attempt to follow Kartesz and Thieret (1991)  in matters of capitalization, spelling, and hyphenation of common names.
Each entry includes the scientific name of the family to which the plant belongs. Note that all of these names end with the suffix "-aceae."
The Element Code is a ten-character code assigned to each element by NatureServe for data management purposes. These codes are common to all Natural Heritage Programs and Conservation Data Centers both within and outside of the United States and allow for efficient interjurisdictional communication. A brief outline of the classification is presented below. Complete coding information is contained in the Natural Heritage Program Operations Manual, TNC, Arlington, Virginia, April 1982, revised June 1988.
Each symbol is composed of the first two letters of the generic name and the first two letters of the specific epithet, plus a tiebreaking number if needed (e.g., CAOB for Calochortus obispoensis, CAEX2 for Calochortus excavatus). Symbols for infraspecific taxa (subspecies or varieties) are composed of the first two letters of the generic name, the first two letters of the specific epithet, and the first letter of the infraspecific epithet, plus a tiebreaking number if needed (e.g., CAPAM for Calochortus palmeri var. munzii, CAPAP4 for Calochortus palmeri var. palmeri).
PLANTS Symbols serve as a convenient shorthand for scientific plant names. They were first used in the Soil Conservation Service’s National List of Scientific Plant Names published in 1971 (revised 1982) and have been used in the PLANTS system ever since. PLANTS Symbols are widely used by the NRCS and other federal agencies (USDA, NRCS 2021).
This field includes scientific names that were used in previous versions of this Inventory, including taxonomic synonyms as well as invalid, misapplied, or unpublished names. We include such synonyms or other names only for tracking and informational/reference purposes. We do not attempt to provide an exhaustive list of all past or alternative scientific names. Other references such as Tropicos, Integrated Taxonomic Information System (ITIS), International Plant Names Index (IPNI), and the primary botanical research literature (e.g., monographs and revisions) are useful for obtaining complete lists of synonyms for plants.
This field indicates the plant’s legal status under the Federal Endangered Species Act (ESA).
|FE||Federally Endangered: The classification provided to a plant in danger of extinction within the foreseeable future throughout all or a significant portion of its range.|
|FT||Federally Threatened: The classification provided to a plant which is likely to become an Endangered species within the foreseeable future throughout all or a significant portion of its range.|
|PE||Proposed Endangered: The classification provided to a plant that is proposed for federal listing as Endangered in the Federal Register under Section 4 of the Endangered Species Act.|
|PT||Proposed Threatened: The classification provided to a plant that is proposed for federal listing as Threatened in the Federal Register under Section 4 of the Endangered Species Act.|
|FC||Federal Candidate: The classification provided to a plant that has been studied by the United States Fish and Wildlife Service, and the Service has concluded that it should be proposed for addition to the list of Federally Endangered and Threatened species.|
|None||The plant has no federal listing status under ESA.|
|FD||Federally Delisted: The plant was previously listed as Endangered or Threatened, but is no longer on the list of Federally Endangered and Threatened species.|
This field indicates the plant’s legal status under the California Endangered Species Act (CESA).
|CE||State Listed as Endangered: The classification provided to a native species or subspecies in serious danger of becoming extinct throughout all or a significant portion of its range due to one or more causes, including loss of habitat, change in habitat, overexploitation, predation, competition, or disease.|
|CT||State Listed as Threatened: The classification provided to a native species or subspecies that, although not presently threatened with extinction, is likely to become an endangered species in the foreseeable future in the absence of special protection and management efforts.|
|CR||State Listed as Rare: The classification provided to a native plant species, subspecies, or variety when, although not presently threatened with extinction, it occurs in such small numbers throughout its range that it may become endangered if its present environment worsens. This designation stems from the Native Plant Protection Act of 1977.|
|CC||Candidate for State Listing: The classification provided to a native species or subspecies that the Fish and Game Commission has formally noticed as being under review by the Department of Fish and Wildlife for addition to the list of endangered or threatened species, or a species for which the commission has published a notice of proposed regulation to add the species to the list of endangered or threatened species.|
|None||The plant has no state listing status under CESA.|
|CD||State Delisted: The plant was previously listed as Endangered, Threatened or Rare but is no longer listed by the State of California.|
The Global Rank (G-rank) is an indication of the overall condition and imperilment of an element throughout its global range. It is a letter+number score that reflects a combination of Rarity, Threat and Trend factors, with weighting being heavier on the rarity factors. The Global Ranks are assigned by NatureServe in coordination with the state program(s) where the element occurs.
|GX||Presumed Extinct — Not located despite intensive searches and virtually no likelihood of rediscovery.|
|GH||Possibly Extinct — Known from only historical occurrences but still some hope of rediscovery. There is evidence that the species may be extinct or the ecosystem may be eliminated throughout its range, but not enough to state this with certainty. Examples of such evidence include 1) that a species has not been documented in approximately 20–40 years despite some searching or some evidence of significant habitat loss or degradation; 2) that a species or ecosystem has been searched for unsuccessfully, but not thoroughly enough to presume that it is extinct or eliminated throughout its range.|
|G1||Critically Imperiled — At very high risk of extinction due to extreme rarity (often 5 or fewer populations), very steep declines, or other factors.|
|G2||Imperiled — At high risk of extinction due to very restricted range, very few populations (often 20 or fewer), steep declines, or other factors.|
|G3||Vulnerable — At moderate risk of extinction or elimination due to a restricted range, relatively few populations (often 80 or fewer), recent and widespread declines, or other factors.|
|G4||Apparently Secure — Uncommon but not rare; some cause for long-term concern due to declines or other factors.|
|G5||Secure — Common; widespread and abundant.|
|GNR||Unranked — Global rank not yet assessed.|
|GU||Unrankable — Currently unrankable due to a lack of information or due to substantially conflicting information about status or trends.|
|G#G#||Range Rank — A numeric range rank (e.g., G2G3) is used to indicate the range of uncertainty about the exact status of a taxon or community.|
|G#T#||Infraspecific Taxon — The status of infraspecific taxa (subspecies or varieties) are indicated by a "T-rank" following the species' Global Rank. Rules for assigning T-ranks follow the same principles as those for Global Ranks. However, a T-rank cannot imply the subspecies or variety is more abundant than the species. In such cases, the G-rank reflects the condition of the entire species, whereas the T-rank reflects the global situation of just the subspecies or variety.|
|?||Qualifier: Inexact Numeric Rank — A question mark represents a rank qualifier, denoting an inexact or uncertain numeric rank.|
|Q||Qualifier: Questionable Taxonomy — The distinctiveness of this entity as a taxon or community at the current level is questionable; resolution of this uncertainty may result in change from a species to a subspecies or hybrid, or inclusion of this taxon or type in another taxon or type, with the resulting taxon having a lower-priority (numerically higher) conservation status rank.|
|C||Qualifier: Captive or Cultivated Only — The taxon or community at present is presumed or possibly extinct or eliminated in the wild across its entire native range but is extant in cultivation, in captivity, as a naturalized population (or populations) outside its native range, or as a reintroduced population or ecosystem restoration, not yet established.|
The State Rank (S-rank) is an indication of the condition and imperilment of an element throughout its range within the state. As with the G-rank, it is a letter+number score that reflects a combination of Rarity, Threat and Trend factors, weighted more heavily on rarity. The State Ranks are assigned by the CNDDB biologists using standard natural heritage methodology.
|SX||Presumed Extirpated — Species is believed to be extirpated from the state. Not located despite intensive searches of historical sites and other appropriate habitat, and virtually no likelihood that it will be rediscovered.|
|SH||Possibly Extirpated (Historical) — Species occurred historically in the state, and there is some possibility that it may be rediscovered. All sites are historical; the element has not been seen for at least 20 years, but suitable habitat still exists.|
|S1||Critically Imperiled — Critically imperiled in the state because of extreme rarity (often 5 or fewer occurrences) or because of some factor(s) such as very steep declines making it especially vulnerable to extirpation from the state.|
|S2||Imperiled — Imperiled in the state because of rarity due to very restricted range, very few populations (often 20 or fewer), steep declines, or other factors making it very vulnerable to extirpation from the nation or state.|
|S3||Vulnerable — Vulnerable in the state due to a restricted range, relatively few populations (often 80 or fewer), recent and widespread declines, or other factors making it vulnerable to extirpation.|
|S4||Apparently Secure — Uncommon but not rare; some cause for long-term concern due to declines or other factors.|
|S5||Secure — Common, widespread, and abundant in the state.|
|SNR||Unranked — State conservation status not yet assessed.|
|SU||Unrankable — Currently unrankable due to a lack of information or due to substantially conflicting information about status or trends.|
|S#S#||Range Rank — A numeric range rank (e.g., S2S3) is used to indicate any range of uncertainty about the status of the species or community.|
|?||Qualifier: Inexact or Uncertain — A question mark represents a rank qualifier, denoting an inexact or uncertain numeric rank.|
Note: References to older ranks may contain a decimal "threat" rank of .1, .2, or .3, where .1 indicates very threatened status, .2 indicates moderate threat, and .3 indicates few or no current known threats.
California Rare Plant Ranks (CRPRs) are a ranking system developed by the California Native Plant Society (CNPS) to define and categorize rarity in the California flora. All plants that are assigned to a California Rare Plant Rank category are tracked by the CNDDB; however, element occurrence (EO) information is only maintained for CRPR 1 and 2 plants, and some CRPR 3 plants. Most CRPR 3 and 4 plants that have EO information in this Inventory and the CNDDB were previously assigned to CRPR 1 or 2; their EO data reflect their prior rank and have generally not been updated since the date of their change to CRPR 3 or 4.
Major changes to California Rare Plant Ranks (e.g., additions, changes, and deletions) undergo the CNPS Rare Plant Status Review process. This is a joint effort by CNPS, the CNDDB, Regional Plant Status Review Groups, the Status Review Forum, and botanical experts throughout the world. Once consensus is reached, then additions, changes, or deletions in California Rare Plant Ranks are made to this Inventory and the CNDDB. For a flow chart of the status review process, see Rare Plant Data in California: The Cooperative Relationship between the California Natural Diversity Database and the California Native Plant Society.
Presumed Extirpated or Extinct — Plants presumed extirpated in California and either rare or extinct elsewhere. These plants have not been seen or collected in the wild in California for many years. A plant is extinct if it no longer occurs anywhere. A plant that is extirpated from California has been eliminated from California, but may still occur elsewhere in its range.
All of the plants constituting California Rare Plant Rank 1A meet the definitions of the California Endangered Species Act of the California Department of Fish and Game Code, and are eligible for state listing. Should these taxa be rediscovered, any impacts to individual plants or their habitat must be analyzed during preparation of environmental documents relating to the California Environmental Quality Act (CEQA), or those considered to be functionally equivalent to CEQA, as they meet the definition of Rare or Endangered under CEQA Guidelines §15125 (c) and/or §15380.
Rare or Endangered — Plants rare, threatened, or endangered in California and elsewhere. These plants are rare throughout their entire range with the majority also being endemic to California. Most of the plants that are ranked 1B have declined significantly over the last century. California Rare Plant Rank 1B plants constitute the majority of taxa in the CNPS Inventory, with more than 1,000 plants assigned to this category of rarity.
All of the plants constituting California Rare Plant Rank 1B meet the definitions of the California Endangered Species Act of the California Department of Fish and Game Code, and are eligible for state listing. Impacts to these species or their habitat must be analyzed during preparation of environmental documents relating to CEQA, or those considered to be functionally equivalent to CEQA, as they meet the definition of Rare or Endangered under CEQA Guidelines §15125 (c) and/or §15380.
Extirpated in California — Plants presumed extirpated in California but common elsewhere. These plants are presumed extirpated because they have not been observed or documented in California for many years. This list only includes plants that are presumed extirpated in California, but are common elsewhere in their range outside of the state.
All of the plants constituting California Rare Plant Rank 2A meet the definitions of the California Endangered Species Act of the California Department of Fish and Game Code, and are eligible for state listing. Should these species be rediscovered, any impacts proposed to individuals or their habitat must be analyzed during preparation of environmental documents relating to CEQA, or those considered to be functionally equivalent to CEQA, as they meet the definition of Rare or Endangered under CEQA Guidelines §15125 (c) and/or §15380.
Rare or Endangered in California — Plants rare, threatened, or endangered in California but common elsewhere. Except for being common beyond the boundaries of California, 2B plants would have been ranked 1B. From the federal perspective, plants common in other states or countries are not eligible for consideration under the provisions of the Federal Endangered Species Act. With California Rare Plant Rank 2B, 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 processes and genetic diversity within species.
All of the plants constituting California Rare Plant Rank 2B meet the definitions of the California Endangered Species Act of the California Department of Fish and Game Code, and are eligible for state listing. Impacts to these species or their habitat must be analyzed during preparation of environmental documents relating to CEQA, or those considered to be functionally equivalent to CEQA, as they meet the definition of Rare or Endangered under CEQA Guidelines §15125 (c) and/or §15380.
Needs Review — Plants about which more information is needed. These plants are united by one common theme—we lack the necessary information to assign them to one of the other ranks or to reject them. Nearly all of the plants constituting California Rare Plant Rank 3 are taxonomically problematic, yet if taxonomically valid would demonstrably qualify for rank 1B or 2B. For each California Rare Plant Rank 3 plant we have provided the known information and indicated in the "Notes" section of the Inventory record where assistance is needed. Data regarding distribution, endangerment, ecology, and taxonomic validity are welcomed and can be submitted by emailing the Rare Plant Program at firstname.lastname@example.org.
Many of the plants constituting California Rare Plant Rank 3 meet the definitions of the California Endangered Species Act of the California Department of Fish and Game Code, and are eligible for state listing. Impacts to these species or their habitat should be analyzed during preparation of environmental documents relating to CEQA, or those considered to be functionally equivalent to CEQA, as they may meet the definition of Rare or Endangered under CEQA Guidelines §15125 (c) and/or §15380.
Uncommon in California — Plants of limited distribution, a watch list. These plants are of limited distribution or infrequent throughout a broader area in California, and their status should be monitored regularly. Should the degree of endangerment or rarity of a California Rare Plant Rank 4 plant change, we will transfer it to a more appropriate rank.
Some of the plants constituting California Rare Plant Rank 4 meet the definitions of the 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 California Rare Plant Rank 4 plants be evaluated for significant impacts during preparation of environmental documents relating to CEQA, or those considered to be functionally equivalent to CEQA, based on CEQA Guidelines §15125 (c) and/or §15380. This may be particularly appropriate for:
To assist in evaluating CRPR 4 taxa for CEQA consideration, see the technical memorandum on Considerations for Including CRPR 4 Plant Taxa in CEQA Biological Resource Impact Analysis prepared by the Rare Plant Program Committee.
California Rare Plant Ranks at each level also include a threat rank (e.g., CRPR 4.3) and are assigned as follows:
|0.1||Seriously threatened in California — Over 80% of occurrences threatened / high degree and immediacy of threat.|
|0.2||Moderately threatened in California — 20-80% of occurrences threatened / moderate degree and immediacy of threat.|
|0.3||Not very threatened in California — Less than 20% of occurrences threatened / low degree and immediacy of threat or no current threats known.|
- Threat ranks do not are provided for general research purposes only and do not indicate differences in conservation assessment. For example, a CRPR 1B.3 plant has the same conservation status as a CRPR 1B.1 plant, and it is mandatory that both be fully considered during preparation of environmental documents relating to CEQA.
- The threat ranking criteria described above represent only the starting point for the assessment of threat level. Other factors, such as habitat vulnerability and specificity, distribution, and condition of occurrences, are also considered in assigning threat ranks.
- In many cases, the threat rank has not been reassessed since the date the taxon was first added to this Inventory or underwent its last Status Review. For these taxa, the assigned threat ranking may not accurately reflect the current level of threat.
A category of Considered but Rejected (CBR) exists for plants that either previously had a CRPR, or that were considered for addition to this Inventory but were rejected for one or more reasons. Any plant that is deleted from a CRPR category in this Inventory is not fully removed and is instead changed to the CBR category. Rejected plants are searchable by selecting the “Considered But Rejected” button in the California Rare Plant Rank section of simple and advanced search. A brief description of the reason why the plant was rejected is included for each CBR entry.
This Other Status field provides additional status listings for a plant, including sensitive designations by federal agencies and the International Union for the Conservation of Nature (IUCN 2021). It also indicates institutions where plant seeds have been accessioned and stored as part of the California Plant Rescue (CaPR) project. CaPR is a collaborative of not-for-profit botanical institutions working under the auspices of the Center for Plant Conservation to conserve the wild species of California and the California Floristic Province, primarily through field work and long-term seed bank collections.
|BLM – Bureau of Land Management||S – Sensitive|
IUCN – International Union for the Conservation of Nature
|CD – Conservation Dependent|
|CR – Critically Endangered|
|DD – Data Deficient|
|EN – Endangered|
|EW – Extinct in the Wild|
|EX – Extinct|
|LC – Least Concern|
|NE – Not Evaluated|
|NT – Near Threatened|
|VU – Vulnerable|
SB – Seed Banked
|BerrySB – Berry Seed Bank|
|CRES – San Diego Zoo CRES Native Gene Seed Bank|
|KewBG – Kew Royal Botanic Gardens|
|CalBG/RSABG – California/Rancho Santa Ana Botanic Garden|
|SBBG – Santa Barbara Botanic Garden|
|UCBG – UC Botanical Garden at Berkeley|
|UCSC – UC Santa Cruz|
|USDA – US Dept of Agriculture|
|USFS – United States Forest Service||S – Sensitive|
This field indicates the California Rare Plant Rank the plant was assigned when it was first added the Inventory, as well as the official add date. The date and description of any subsequent status change(s) (including changes in Threat Rank) are also recorded here. For the most part, this field only shows additions or changes that transpired after the last print edition of the Inventory was published in 2001, since the first Inventory database was created shortly thereafter. The 50 most recent additions and changes in CRPR also appear in the Additions / Changes / Deletions section of the Inventory home page.
This field indicates the official date that the plant was added to the Inventory.
This field indicates the date that any data fields were edited. Note, the date edited is not limited to edits in the Conservation Status section and applies to edits made to any of the species’ details.
The information presented in the ecology and life history section has been developed and updated from a variety of sources, including published and unpublished literature/reports, field survey forms, personal communications, herbarium specimen data, and photos.
This field includes a brief description of the duration and growth form of the plant. It also includes leaf condition, specialized habitat, and mode of nutrition for plants and lichens as applicable.
For herbaceous plants only:
For shrubs, trees, and vines only:
For plants only:
For lichens only:
In some plant species, the growth form can vary depending on geography and local environmental conditions. Perennials that are suffrutescent herbs or subshrubs present special difficulties. If these plants die back seasonally to the ground or to a small crown of woody tissue, then we classify them as herbs. If they retain much or all of their woody above-ground tissue, then we call them shrubs.
This field indicates the month(s) of the year when the plant is typically in bloom. For ferns and other spore-bearing plants, we give the months when spores are released and spore-bearing structures such as sori are typically present on the plant. We do not include any comparable information for gymnosperms, non-vascular plants, or lichens. Months included in parentheses are uncommon.
The plant’s upper and lower elevational limits in California are specified in both meters and feet (rounded to the nearest five).
This field briefly describes one or more habitats in which a rare, threatened, or endangered plant is typically found. In cases where a plant’s specific habitat occurs within a broader matrix of another habitat, both of these habitats are usually listed. For example, a rare plant from Meadows and seeps occurring in a matrix of Upper montane coniferous forest would typically have its habitat presented as "Meadows and seeps, Upper montane coniferous forest."
Habitat descriptions follow those outlined by Robert F. Holland and John O. Sawyer, Jr. and are presented in taxonomic rather than alphabetical order. Please refer to Holland (1986) for a more complete discussion of the habitat types and their classification.
The habitat information presented in this Inventory should not be used to predict whether rare plants are likely to occur on a particular project site. Field surveys for rare plants should instead be floristic in nature, meaning that every plant occurring in a project area should be identified to the taxonomic level necessary to determine its rarity and listing status. “Focused surveys” that are limited to habitats known to support rare plants are insufficient since they are not floristic in nature (for additional information, see Protocols for Surveying and Evaluating Impacts to Special Status Native Plant Populations and Natural Communities by the California Department of Fish and Wildlife).
|Coastal dunes||CoDns||Herbs or shrubs on coastal sand deposits from Del Norte to San Diego counties. Cover usually low near the beach, increasing with distance from salt spray and blowing sand.|
|Desert dunes||DeDns||Sand accumulations east of the Pacific Crest from Modoc to Imperial counties. Vegetation on desert dunes varies considerably. Active dunes usually support only sparse herbs and grasses, but partially stabilized or stabilized dunes often will support shrubs, including mesquite and creosote bush.|
|Inland dunes||InDns||Sand accumulations in and around the Great Valley supporting mostly herbs, although shrubs may be locally important.|
|Coastal bluff scrub||CBScr||Dense shrubs, prostrate to 1–2 meters tall. Typically on fairly steep, rocky sites exposed to considerable wind and salt spray because of proximity to the ocean. Many plants succulent, especially to the south. Found from Del Norte to San Diego counties.|
|Coastal scrub||CoScr||Dense shrubs 0.5–2 meters tall with scattered grassy openings. Many plants dormant, even deciduous, during periods of water stress. Most sites have shallow rocky soils, frequently with a southern or western exposure. Many taxa adapted to fire by stump sprouting or high seed production.|
|Sonoran Desert scrub||SDScr||Widely scattered creosote bushes with the space between them sometimes occupied by ephemeral, colorful shows of annuals following particularly wet winters. Succulents and microphyllous trees conspicuous, especially in rocky environments. The part of Munz's (1959) "Creosote bush scrub" found roughly south of the San Bernardino / Riverside county line.|
|Mojavean Desert scrub||MDScr||Widely scattered creosote bushes with the space between them sometimes occupied by ephemeral, colorful shows of annuals following particularly wet winters. At elevations of 600 meters or higher; succulents and microphyllous trees lacking. This habitat type constitutes most of Munz's (1959)  "Creosote bush scrub" found north of the San Bernardino / Riverside county line.|
|Great Basin scrub||GBScr||Shrubs, ranging in height from very short, <20 centimeters, on very cold sites or shallow soils to 1–2 meters tall on warmer sites where soils are deeper. Perennial grasses occupy much of the space between shrubs. Found on the Modoc Plateau, High Cascade Range, Warner Mountains, High Sierra Nevada, East of the Sierra Nevada, and North Coast Ranges.|
|Chenopod scrub||ChScr||Usually gray, intricately branched, microphyllous shrubs most commonly on fine-textured, alkaline and/or saline soils in areas of impeded drainage. Diversity usually low to monotonous. Saltbushes and greasewood frequently dominate. This vegetation occurs from Modoc County south to Mexico, including parts of the Great Valley and Inner South Coast Ranges.|
|Chaparral||Chprl||Impenetrably dense, evergreen, leathery-leaved shrubs that are active in winter, dormant in summer, and adapted to frequent fires either through resprouting or seed carry-over. There is a characteristic florula of fire-following annuals and short-lived perennials. Mature stands may exceed 3-4 meters in height. It occurs on diverse substrates, many of which support distinctive suites of edaphic indicators. Chaparral may be successional to coniferous forest or oak woodland, as tree seedlings can sometimes be found beneath the shrub canopy.|
|Coastal prairie||CoPrr||Dense, fairly tall <1 meter perennial sod- and tussock-forming grasses and grass-like herbs. Occurs in two distinct settings: sandy marine terraces within the zone of coastal fog (usually <350 meters elevation, within a matrix of Northern Coastal Scrub), or on fine-textured soils of ridgetops beyond coastal fogs (usually >750 meters, within a matrix of Mixed Evergreen or North Coastal Coniferous Forest). Intermittent from the Santa Cruz area north to southern Oregon.|
|Great Basin grassland||GBGrs||Perennial sod-forming and bunch grasses. Presumably once widespread on the Modoc Plateau and in northeastern California. Currently represented as scattered, mostly small, islands in areas where grazing pressure has been low and fire frequencies higher than surrounding scrubs. Both upland and bottom-land forms occur.|
|Valley and foothill grassland||VFGrs||Introduced, annual Mediterranean grasses and native herbs. On most sites the native bunch grass species, such as needle grass, have been largely or entirely supplanted. Stands rich in natives usually found on unusual substrates, such as serpentinite or somewhat alkaline soils.|
|Vernal pools||VnPls||Seasonal amphibious environments dominated by annual herbs and grasses adapted to germination and early growth under water. Spring desiccation triggers flowering and fruit set, resulting in colorful concentric bands around the drying pools.|
|Meadows and seeps||Medws||More-or-less dense grasses, sedges, and herbs that thrive, at least seasonally, under moist or saturated conditions. They occur from sea level to treeline and on many different substrates. They may be surrounded by grassland, forest, or shrubland.|
|Playas||Plyas||Non-vascular plants and sparse, gray shrubs on poorly drained soils with usually high salinity and/or alkalinity due to evaporation of water from closed basins. Found from the Modoc Plateau to Sonoran Desert and in the San Joaquin Valley.|
|Pebble or pavement plain||PbPln||Herb- and grass-dominated openings of low cover, dominated by several cushion-forming plants endemic to dense, clay soils armored by a lag gravel of quartzite pebbles. Many of the dominant taxa are themselves rare plants. Found only in the San Bernardino Mountains.|
|Bogs and fens||BgFns||Wetlands, typically occupying sites sub-irrigated by cold, frequently acidic, water. Plant growth dense and low growing, dominated by perennials herbs or low shrubs. Saturated soils frequently allow substantial accumulations of "peat." From the Klamath Ranges to North Coast Ranges, along the North Coast and in the northern Sierra Nevada.|
|Marshes and swamps||MshSw||Emergent, suffrutescent herbs adapted to seasonally or permanently saturated soils. These include salt, brackish, alkali, and fresh water marshes, as well as swamps with their woody dominants and hydrophytic herbs. Found sporadically throughout California.|
|Riparian forest||RpFrs||Broadleaved, winter-deciduous trees, forming a closed canopy, associated with low- to mid-elevation perennial and intermittent streams in every county and climatic region of California. Most stands even-aged, reflecting their flood-mediated, episodic reproduction.|
|Riparian woodland||RpWld||Broadleaved, winter-deciduous trees and forming an open canopy, associated with low- to mid-elevation streams. Most stands even-aged, reflecting their flood-controlled, episodic reproduction. This type tends to occupy more intermittent streams, often with cobbly or bouldery bedloads.|
|Riparian scrub||RpScr||Streamside thickets dominated by one or more willows and other fast-growing shrubs or vines. Most plants recolonize following flood disturbance.|
|Cismontane woodland||CmWld||Trees deciduous or evergreen, forming an open canopy. Broadleaved trees, especially oaks, dominate, although conifers may be present as canopy emergents. The understory may be open and herbaceous or closed and shrubby. This type occurs on a variety of sites in lowland California.|
|Pinyon and juniper woodland||PJWld||Open stands of round-topped conifers to 5 meters in height. The understory is frequently comprised of shrubs and herbs seen in adjacent stands lacking trees. Often forms a broad ecotone between higher-elevation forest and lower elevation scrubland or grassland. Found mostly in the Mojave Desert mountains and east of the Cascade-Sierran crest.|
|Joshua tree woodland||JTWld||Joshua trees form an open canopy and are usually the only arborescent species present. The understory is typically a diverse mixture of microphyllous, evergreen shrubs, semi-deciduous shrubs, semi-succulents, and succulents. Found mostly in the Mojave Desert.|
|Sonoran thorn woodland||STWld||Succulents, microphyllous herbs and shrubs, especially of rocky environments. Tree-like plants are visually dominant.|
|Broadleaved upland forest||BUFrs||Stands of evergreen or deciduous, broadleaved trees 5 meters or taller, forming a closed canopy. The understory in many cases is poorly developed. Sometimes seral to montane coniferous forest. Includes the "mixed evergreen forest" of the Coast Ranges.|
|North Coast coniferous forest||NCFrs||Needle-leaved evergreen trees in usually quite dense stands that may attain impressive heights. Usually on well-drained, moist sites within the reach of summer fog, but not experiencing much winter snow. Occurs in the wetter parts of the North Coast Ranges.|
|Closed-cone coniferous forest||CCFrs||Dense stands dominated by serotinous-coned conifers. Most stands are even-aged due to fire establishment. Usually associated with sterile, rocky soils, strong and steady winds, and impaired drainage. Many open stands have an understory composed of chaparral or coastal scrub species. Found in most areas except for the Great Valley and deserts.|
|Lower montane coniferous forest||LCFrs||Open to dense stands of conifers found at lower and middle elevations in the mountains. Broadleaved trees may be present in the understory. Dense chaparral shrubs may also occur, especially in seral stands. The upper limit of lower montane coniferous forests more-or-less coincides with the elevation of maximum annual precipitation.|
|Upper montane coniferous forest||UCFrs||Open to dense coniferous forest, found at high elevations in the mountains. Trees tend to be somewhat shorter than at lower elevations. The understory tends to be open, drawn from adjacent montane chaparral species, or lacking. Found above the elevation of maximum precipitation, with the growing season curtailed by accumulation of winter snow.|
|Subalpine coniferous forest||SCFrs||Dense to open coniferous forest found at the highest elevations of tree establishment. Occurs in areas where substantial snowpack accumulation and cold temperatures limit the growing season to three months or less.|
|Alpine boulder and rock field||AlpBR||Fell-fields, talus slopes, and meadows found above the forest line. Favorable sites may develop continuous turf, but in most areas plants are tucked between large nurse rocks that provide protection from harsh winter conditions.|
|Alpine dwarf scrub||AlpDS||Compact, woody subshrubs occurring above the forest line, adapted to a short growing season resulting from cold air temperatures, snow accumulation, and harsh winter winds.|
Habitat modifiers may be briefly described in parentheses immediately following the general habitat descriptor. For example, a habitat entry of “Meadows and seeps (edges), Upper montane coniferous forest” indicates the plant is known to occur only along the edges of meadows and seeps, but is not restricted to edges when occurring in upper montane coniferous forest.
The typical habitat modifiers used in this Inventory generally conform to the same micro habitat descriptors listed in the table below. In some cases, different descriptors may be used.
This field may include a brief description of the micro habitat. It is generally used when a micro habitat descriptor does not exist or a longer description of micro habitat details is desirable (e.g., to list associated species or indicate complex micro habitat details).
This field may include one or more micro habitat descriptor. The most often used descriptors are shown in the following table:
|Typical Micro Habitat Descriptors|
Freshwater (for Marshes and swamps)
Coastal salt (for Marshes and swamps)
Maritime (for Chaparral)
Many entries include additional notes. We have made a special effort to indicate missing information about endangerment or taxonomy, in the hope that knowledgeable users will fill in the gaps.
In this new version of the Inventory, the notes have been separated into four different categories as defined below. The "References" category has been removed and developed into its own field that is defined in the "Selected References" section of this glossary. We are currently in the process of parsing the content of the original "Notes" field into these specific categories. This will increase our efficiency in updating and maintaining the different types of notes, while also enabling a better user experience in finding specific information by category.
Abbreviations that are commonly used in the notes include:
|ACEC||Area of Critical Environmental Concern|
|AFB||Air Force Base|
|BLM||Bureau of Land Management|
|CalTrans||California Department of Transportation|
|CDFW||California Department of Fish and Wildlife|
|DOD||United States Department of Defense|
|HCP||Habitat Conservation Plan|
|RNA||Research Natural Area|
|TNC||The Nature Conservancy|
|USFS||United States Forest Service|
|USFWS||United States Fish and Wildlife Service|
This field contains the original notes from prior editions with all category types combined.
Includes information on significant threats to the plant over its range in California. We have placed a greater emphasis on noting threats for plants with relatively few occurrences. “Possibly threatened by...” is used for uncertain threats, and “Potentially threatened by...” for anticipated future threats.
Noted threats include but are not limited to the following:
Foot traffic (from people)
Flood control projects
Border Patrol activities
Alteration of fire regimes
Climate change and other pervasive human impacts that pose a threat to many rare plants are generally omitted from the notes.
Relevant notes on taxonomy. Example entries include “Can be confused with _____...”, “Possibly a variant of _____...”, “Intergrades with _____...”, or “Related to _____; needs further study.”
Any relevant notes that do not fit within the other note categories, including comments on management, date of last observation/rediscovery, and possible list changes (usually for CRPR 3 plants, such as “Move to CRPR 1B?” along with a call for relevant information).
Where available, a summary of element occurrence (EO) data is included from the California Department of Fish and Wildlife’s Natural Diversity Database (CNDDB). These data are available for all CRPR 1 and 2 plants and only some CRPR 3 and 4 plants. Most CRPR 3 and 4 plants that have EO data in this section were previously assigned to CRPR 1 or 2; their EO data is a reflection of their prior rank and have generally not been updated since the date of their change to CRPR 3 or 4. (Note, if EO data are not available for a CRPR 1 or 2 plant in this Inventory, this usually indicates it is a recent addition and that the data are not yet included in the CNDDB.)
Element occurrences are defined by the CNDDB as a population or group of populations found within ¼ of a mile of each other.
The current total number of element occurrences in California for a particular plant.
An element's Occurrence Rank is a ranking of the quality of the habitat and the condition of the population at that location. The possible values for Occurrence Rank along with their descriptions are as follows:
|A: Excellent viability||Occurrence exhibits optimal or at least exceptionally favorable characteristics with respect to population size and/or quality and quantity of occupied habitat; and, if current conditions prevail, the occurrence is very likely to persist for the foreseeable future (i.e., at least 20–30 years) in its current condition or better. These occurrences have characteristics (e.g., size, condition, landscape context) that make them relatively invulnerable to extirpation or sustained population declines, even if they have declined somewhat relative to historical levels. For species associated with habitat patches or ephemeral or particularly dynamic habitats, occurrences warranting an A rank generally consist of metapopulations rather than single demes (unless exceptionally large and robust). Occurrences of this rank typically include at least 1,000 mature individuals but may be smaller (100s) or might require larger populations (10,000s), depending on the species and its demographic characteristics. However, occurrences can be ranked A even if population size is not known. For example, for occurrences lacking information on population size, an A rank may be appropriate under the following circumstances: the population is clearly very large but it is not known how large; the area of occupied habitat is exceptionally large; or the occurrence has excellent condition and landscape context and a long history of occurrence persistence. Occurrences with excellent estimated viability are ranked A even if one or more other occurrences have a much larger population size and/or much greater quantity of occupied habitat. In most cases, occurrences ranked A will occupy natural habitats. However, "natural" is an ambiguous concept, and occurrences in "unnatural" conditions (e.g., somewhat modified by human actions) may still be assigned a rank of A if they otherwise meet the criteria.|
|B: Good viability||Occurrence exhibits favorable characteristics with respect to population size and/or quality and quantity of occupied habitat; and, if current conditions prevail, the occurrence is likely to persist for the foreseeable future (i.e., at least 20–30 years) in its current condition or better. B-ranked occurrences have good estimated viability and, if protected, contribute importantly to maintaining or improving the conservation status of threatened or declining species.|
|C: Fair viability||Occurrence characteristics (size, condition, and landscape context) are non-optimal such that occurrence persistence is uncertain under current conditions, or the occurrence does not meet A or B criteria but may persist for the foreseeable future with appropriate protection or management, or the occurrence is likely to persist but not necessarily maintain current or historical levels of population size or genetic variability. This rank may be applied to relatively low-quality occurrences with respect to size, condition, and/or landscape context if they still appear to have reasonable prospects for persistence for the foreseeable future (at least 20–30 years).|
|D: Poor viability||If current conditions prevail, occurrence has a high risk of extirpation (because of small population size or area of occupancy, deteriorated habitat, poor conditions for reproduction, ongoing inappropriate management that is unlikely to change, or other factors).|
|X: Extirpated||Adequate surveys by one or more experienced observers at times and under conditions appropriate for the species at the occurrence location, or other persuasive evidence, indicate that the species no longer exists there or that the habitat or environment of the occurrence has been destroyed to such an extent that it can no longer support the species.|
|U: Unknown||An occurrence rank cannot be assigned due to lack of sufficient information on the occurrence.|
Displays the number of element occurrences that have been seen within the past 20 years. Element occurrences last seen more than 20 years ago are considered historical and are a priority to revisit as part of the Rare Plant Treasure Hunt (RPTH) program.
The number of occurrences not seen within the past 20 years.
The number of occurrences seen within the past 20 years.
Presence refers to the condition of the occurrence when it was last observed. The three possible values of Presence are totaled across all occurrences and are described as follows:
The total number of occurrences that are presumed to be extant (still in existence). An occurrence is presumed extant until evidence to the contrary is received by the CNDDB.
The total number of occurrences that are possibly extirpated (locally extinct, destroyed). Evidence of habitat destruction or population extirpation has been received by the CNDDB for this site, but questions remain as to whether the element still exists.
The total number of occurrences that are presumed extirpated (locally extinct, destroyed). Only used when the element has been searched for but not seen for many years or when the habitat is destroyed at this site.
The distribution of the plant is described by USGS quad, county, and island within California, together with other states or countries where the plant is known 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 Monterey pine (Pinus radiata) is widely planted within the state, we track only the few natural occurrences of this plant. When we indicate that a plant occurs in a particular quad or county, we are making a positive statement that is based upon specimens, photographs, literature, or field observations. In no way does this imply that a plant does not occur in other quads or counties in California or in other states. Our understanding of plant distribution is constantly improving, and new localities for rare plants are being discovered often in unpredicted circumstances. Species may be present in other areas where conditions are favorable, and these data must not be substituted for pre-project review or on-site botanical surveys.
Indicates whether the plant is endemic (native and restricted) only to California.
Indicates whether the plant is indigenous to one or more of the California islands, including the Farallon Islands off the coast of San Francisco and/or one or more of the eight Channel Islands off the coast of Santa Barbara, Ventura, and Los Angeles counties.
Here we list the state(s) in addition to California where the plant is indigenous. Standard, two-letter state abbreviations are included in parentheses after the full state name (also used in the “Notes” section for some plants).
|AL||Alabama||IL||Illinois||NC||North Carolina||SC||South Carolina|
|AK||Alaska||IN||Indiana||ND||North Dakota||SD||South Dakota|
|District Of Columbia|
Three-letter codes are used to indicate the known county and island distribution within California (also used in the "Notes" section for some plants).
|FRE||Fresno||SBA||Santa Barbara||ANA||Anacapa Isl.|
|GLE||Glenn||SBD||San Bernardino||FAR||Farallon Isl.|
|HUM||Humboldt||SBT||San Benito||SBR||Santa Barbara Isl.|
|IMP||Imperial||SCL||Santa Clara||SCM||San Clemente Isl.|
|INY||Inyo||SCR||Santa Cruz||SCT||Santa Catalina Isl.|
|KNG||Kings||SDG||San Diego||SCZ||Santa Cruz Isl.|
|KRN||Kern||SFO||San Francisco||SMI||San Miguel Isl.|
|LAK||Lake||SHA||Shasta||SNI||San Nicolas Isl.|
|LAS||Lassen||SIE||Sierra||SRO||Santa Rosa Isl.|
|MAD||Madera||SJQ||San Joaquin||BA||Baja California|
|MPA||Mariposa||SLO||San Luis Obispo||GU||Isla Guadalupe, Baja|
|MRN||Marin||SMT||San Mateo||SA||South America|
Where known, the United States Geological Survey (USGS) 7.5 minute quadrangle (Quad) names are listed and displayed on a map. As with counties, the distribution by USGS quad(s) is based on known occurrences. We do not mean to imply that a plant does not occur on a topographic quad we have not listed; rather, it may be present but has yet to be discovered, or the data have not yet become available to the CNDDB.
The USGS quad code consists of one degree blocks sub-divided into sixty-four 7.5 minute maps. The one degree block is referenced by the latitude and longitude of its southeast corner (e.g., 38121). Individual maps within the block are referenced by an alpha-numeric code. This code originates at the same southeast corner as the one degree block and runs numerically east to west, and alphabetically south to north. This creates a grid allowing maps to be coded by the intersection of these axes (e.g., B5). A complete map code would be 38121B5. The CNDDB quad code converts this value to an integer by replacing the alpha character with a numeric equivalent (A = 1, B = 2, C = 3, D = 4, E = 5, F = 6, G = 7, H = 8).
In prior editions, this Inventory employed a modified version of the quad numbering system previously used by the California Department of Water Resources (DWR). The DWR codes consisted of three numbers by followed by the letter A, B, C, or D and were used in the “Notes” section for some plants. The abbreviated codes have been discontinued in favor of using the CNDDB quad codes.
For CRPR 3 and 4 plants, quad data are not quality controlled and may be incomplete, inaccurate, or out of date.
The following symbols are used as modifiers following county, quad, and/or state codes to express extirpation and/or uncertainty in extirpation:
- Presumed extirpated
- (?) Occurrence confirmed, but possibly extirpated
The states as well as Baja California, Isla Guadalupe, Sonora Mexico, and South America where the plant is indigenous are indicated on a regional map. Each state or region where the plant occurs includes an overlay. Since over half of the plants in this Inventory are endemic to California, the map will often only display an overlay of California.
The quads and counties comprising the known distribution are indicated on a topographic map of California. Counties and/or quads can be toggled on/off by selecting radio buttons, and the basemap can also be switched from topo to aerial (satellite). Clicking on a quad or county will pop up its name and numerical code/abbreviation.
Selected references are given and are listed in order of reference descriptors. Reference names or titles are given preceding one of the following descriptors:
|CNPS Status Review||The status review document signifying the plant’s California Rare Plant Rank addition, change, or deletion in the CNPS Inventory and CNDDB.|
|CNPS Name Change||The name change review document signifying the plant’s taxonomic name change in the CNPS Inventory and CNDDB.|
|Original Description||The original description of the plant.|
|Revised Nomenclature||Where the current name for the plant was published, if different from the original description.|
|Taxonomic Treatment||Description or revision of the taxonomic concept of the plant.|
|Species Account||general information on the plant, usually of a non-taxonomic nature. This descriptor includes Species of Conservation Concern (SCC) Accounts developed by CNPS for plants that meet the criteria for potential SCC on one or more forests in the US Forest Service Pacific Southwest Region. (See here for additional information on the SCC Accounts.)|
|Other||Entries that do not conform to the above descriptors.|
In previous Inventory editions, references prior to 1850 were omitted; however, with many older texts becoming scanned and accessible in open access digital libraries, such as the Biodiversity Heritage Library (BHL), we have started to include these older references.
- 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.
- California Department of Fish and Wildlife, Natural Diversity Database. 2021. CNDDB Maps and Data. Website https://wildlife.ca.gov/Data/CNDDB [accessed 19 May 2021].
- Holland, R. F. 1986. Preliminary Descriptions of the Terrestrial Natural Communities of California. Nongame-Heritage Program, California Department of Fish and Wildlife. Sacramento, CA. 156 pp.
- IUCN. 2021. The IUCN Red List of Threatened Species. Version 2021-1. Website https://www.iucnredlist.org [accessed 19 May 2021].
- Jepson Flora Project (eds.) 2021. Jepson eFlora. Website https://ucjeps.berkeley.edu/eflora/ [accessed 19 May 2021].
- 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, J. R. 1993. How plants get their names and why names change. Fremontia 21(1): 19-24.
- Skinner, M. W. and B. Ertter. 1993. Whither rare plants in The Jepson Manual? Fremontia 21(3): 23-27.
- Turland, N. J., J. H. Wiersema, F. R. Barrie, W. Greuter, D. L. Hawksworth, P. S. Herendeen, S. Knapp, W.-H. Kusber, D.-Z. Li, K. Marhold, T. W. May, J. McNeill, A. M. Monro, J. Prado, M. J. Price, and G. F. Smith (eds.). 2018. International Code of Nomenclature for algae, fungi, and plants (Shenzhen Code) adopted by the Nineteenth International Botanical Congress Shenzhen, China, July 2017. Regnum Vegetabile 159. Glashütten: Koeltz Botanical Books. DOI https://doi.org/10.12705/Code.2018
- USDA, NRCS. 2021. PLANTS Help, The PLANTS Database. National Plant Data Team, Greensboro, NC. Website http://plants.usda.gov/. Document available at https://plants.sc.egov.usda.gov/assets/docs/PLANTS_Help_Document.pdf [accessed 19 May 2021].