CNPS Inventory
of Rare Plants

Astragalus pycnostachyus lanosissimus. Credit David Magney.

The CNPS Inventory of Rare and Endangered Plants is a widely-recognized resource that directly guides rare plant protection, conservation planning, and land acquisition and management in California. CNPS published the first edition of its Inventory of Rare and Endangered Plants in 1974, and published its last print edition (V. 6) in 2001. In 2001, the Inventory switched to being online (V. 7, developed and maintained by Larry Levine), and is currently in its 8th edition.

Today, the 8th edition is available online, where conservationists, consultants, planners, researchers, and resource managers use it on a daily basis to help educate landowners and public policy makers about the importance of rare plant stewardship and conservation. Individuals preparing environmental documents California Environmental Quality Act (CEQA) review often use the Inventory to determine the potential for resource conflicts and to develop project-specific lists of rare plants to target during botanical surveys. Conservationists and resource managers use the same information to review environmental documents and prepare public testimony to influence decision-makers.

Inventory Details

California Rare Plant Ranks

  • California Rare Plant Rank 1A: Plants presumed extirpated in California and either rare or extinct elsewhere
  • California Rare Plant Rank 1B: Plants rare, threatened, or endangered in California and elsewhere
  • California Rare Plant Rank 2A: Plants presumed extirpated in California but common elsewhere
  • California Rare Plant Rank 2B: Plants rare, threatened, or endangered in California but more common elsewhere
  • California Rare Plant Rank 3: Review List: Plants about which more information is needed
  • California Rare Plant Rank 4: Watch List: Plants of limited distribution

Full CNPS Rare Plant Rank definitions

Considered but rejected taxa

See Considered but Rejected Taxa for plants that have been considered by CNPS but subsequently rejected for inclusion in the Inventory, as well as a list of species that have been postponed, are provided here.

If you have information that any of these taxa deserve inclusion in the CNPS Inventory, please let us know by contacting CNPS Rare Plant Botanist Aaron Sims at 916/324-3816 or asims@cnps.org.

Taxa not included in the inventory and why

CNPS has tracked plants that are rare from a statewide perspective since the late 1960s with more than 2,000 taxa currently ranked as rare statewide. However, even if a species is not included in the CNPS Inventory, it does not necessarily mean that the species is not rare.

A number of attention-worthy plants may not be included in the CNPS Inventory for a number of complex reasons, including:

  • Locally rare but not statewide — Many plants that are not rare from a statewide perspective may nonetheless be rare from a regional perspective (see Locally Rare Plants discussion).
  • Changes over time — Species that were once considered to be too common or that were not thought to occur in California (‘considered but rejected’ taxa), may have become rare or have subsequently been found in California. Updates are ongoing.
  • Missing data — Species that are on the list of postponed taxa may in fact be rare and would especially benefit from collection of information so that an accurate assessment of their rarity can be made. See below for a list of Postponed Taxa.
  • Not yet surfaced — There are also taxa that have not yet been brought to the attention of CNPS as rare or that are in the CNPS backlog of rare taxa scheduled to undergo review for inclusion in the CNPS Inventory. If you know of a plant that should be considered for inclusion in the CNPS Inventory, please submit a sponsorship form (.doc).

Postponed taxa

The CNPS Postponed Taxa is a list of approximately 300 taxa, which were considered as possible new additions during the development of the CNPS Inventory 6th edition and our ongoing data review process, but were “postponed” due to significant taxonomic uncertainty and/or lack of information regarding distribution, abundance, rarity and/or endangerment.

Interpreting lists from past editions in relation to California Rare Plant Ranks

1st Edition:

  • Very Rare and Rare and Endangered Plants (pp. 12-32), mostly represents what is currently considered CRPR 1A and 1B.
  • Appendix I, Rare and Not Endangered Plants (Including Some of Uncertain Status) (pp. 33-40), mostly represents what is currently considered CRPR 2B.
  • Appendix II, Plants Not Rare But Mostly of Limited Distribution (pp. 41-42), mostly represents what is currently considered CRPR 4.

2nd Edition:

  • List 1- Plants Presumed Extinct, represents what is currently considered CRPR 1A.
  • List 2- Plants Rare and Endangered, represents what is currently considered CRPR 1B.
  • List 3- Plants Rare, But Not Endangered, represents what is currently considered CRPR 4.
  • List 4- Plants Rare in California, Common Elsewhere, represents what is currently considered CRPR 2B.

3rd to 6th Editions:

  • Lists correspond to current CRPRs.
Caulanthus californicus

Online Inventory

Access the online database.

Visit RPI

Previous Editions

Inventory cover, 1st Edition
1st Edition (1974)

Inventory cover, 2nd Edition
2nd Edition (1980)
Supplement 1 (1981)
Supplement 2 (1982)

Inventory cover, 3rd Edition
3rd Edition (1984)

Inventory cover, 4th Edition
4th Edition (1988)


5th Edition (1994)


6th Edition (2001)

Lichens of Conservation Concern

In collaboration with the California Lichen Society’s (CALS) Conservation Committee, the CNPS Rare Plant Program began including Lichens of Conservation Concern in the CNPS Inventory in 2014.

As with vascular and non-vascular plants in the Inventory, the CNPS Rare Plant Program updates and maintains information on rare lichens through contributions from botanists along with the review of data submitted to the CNDDB. Unlike vascular and non-vascular plants, however, additions and status changes to lichens in the Inventory are based on the CALS Conservation Committee’s sponsorship process instead of the Rare Plant Status Review Process. For additional information about Lichens of Conservation Concern, please view their sponsorships available on the CALS website, as well as the data provided on them in the Online Inventory.

Support the Inventory!

The 8th Online edition would not have been possible without generous supporters. CNPS offers our sincere appreciation for these financial contributions, as well as the combined efforts of many others who’ve helped make this resource possible. To support ongoing enhancements to the Inventory, please contact CNPS Executive Director Dan Gluesenkamp or use the donate button below.

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