CPC Plant Profile: Thorne's Royal Larkspur
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Plant Profile

Thorne's Royal Larkspur (Delphinium variegatum ssp. thornei)

This shot shows several plants in situ. Photo Credit: Dylan Hannon
  • Global Rank: T1 - Critically Imperiled
  • Legal Status: N/A
  • Family: Ranunculaceae
  • State: CA
  • Nature Serve ID: 128015
  • Date Inducted in National Collection: 03/08/1989

Three varieties of Delphinium variegatum are known. One, D. var. variegatum, is found along the coast and foothills of central and northern California. Another is the Federally Endangered D. var. kinkiense, or San Clemente Island larkspur, which is endemic to (found only on) San Clemente Island, one of the Channel Islands. The subspecies under the care the Center for Plant Conservation is D. var. thornei, or Thorne's larkspur. This subspecies is also endemic to San Clemente, and also considered rare, even more so than the San Clemente Island larkspur. However, this rarest subspecies has no special legal status, although the U.S. Fish and Wildlife Service considers it to be a species of concern. The San Clemente Island larkspur occurs mainly on the northern end of the island, while Thorne's larkspur occurs mainly on the south. However, the two rare subspecies of San Clemente Island have been the subject of recent study, because there is considerable overlap in their ranges. To date, the only way to consistently distinguish one from the other is by sepal color, with Thorne's larkspur having light blue to bright blue flowers and the endangered San Clemente Island larkspur having white to light blue flowers. Populations that occur in the center of the island have individual plants with white, bright blue, and intermediate flower colors, suggesting that the two subspecies may be hybridizing. (Dodd and Helenurm 2000, 2002)

Participating Institutions
CPC's Plant Sponsorship Program provides long term stewardship of rare plants in our National Collection. We are so grateful for all our donors who have made the Plant Sponsorship Program so successful. We are in the process of acknowledging all our wonderful plant sponsorship donors on our website. This is a work in progress and will be updated regularly.
  • 09/01/2020
  • Orthodox Seed Banking

Based on an September 2020 extract of the California Plant Rescue Database, California Botanic Garden holds 2 accessions of Delphinium variegatum subsp. thornei in orthodox seed collection. There are as many as 1460 seeds of this species in their collection - although some may have been used for curation testing or sent to back up.

  • 08/05/2020
  • Seed Collection

Based on an August 2020 extract of the California Plant Rescue Database, California Botanic Garden has collected 2 seed accessions of Delphinium variegatum subsp. thornei from 2 plant occurrences listed in the California Natural Diversity Database. These collections together emcompass 2 maternal plants

Nature Serve Biotics
  • 05/02/2017

Restricted to San Clemente Island, California; small number of sites on the island, may be highly threatened by feral animals.

  • 01/01/2010

The recent removal of goats from the island has removed the only known threat to this species. (USFWS 1996)

  • 01/01/2010

Roughly 13,000 individuals are known from 13 populations. (USFWS 1996)

  • 01/01/2010

Recent and ongoing research has been performed on Delphinium variegatum and its three subspecies (var. variegatum, var. kinkiense, var. thornei). Research includes floral variation and genetic diversity. (Dodd and Helenurm 2000, 2002)

  • 01/01/2010

The U.S. Navy has jurisdiction over San Clemente Island, has an ongoing program to remove feral goats and pigs in an effort to restore the native vegetation. (CDFG 2002)

  • 01/01/2010

Keep feral goats and pigs out of populations of this species. Ensure that invasive species are kept in check on San Clemente Island.

  • 01/01/2010

Maintain a genetically representative seed bank.


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Taxon Delphinium variegatum ssp. thornei
Authority Munz
Family Ranunculaceae
CPC Number 1389
ITIS 18522
Common Names Thorne's royal larkspur | royal larkspur
Associated Scientific Names Delphinium variegatum ssp. thornei
Distribution Delphinium variegatum ssp. thornei (Thorne's royal larkspur) is restricted to southern San Clemente Island. (Dodd and Helenurm 2002)
State Rank
State State Rank
California S2

Open grassy hills and woods

Ecological Relationships


Common Name Name in Text Association Type Source InteractionID
Lead Institution State Reintroduction Type Year of First Outplanting

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