CPC Plant Profile: Slender-petal Thelypody
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Plant Profile

Slender-petal Thelypody (Thelypodium stenopetalum)

Thelypodium stenopetalumin flower Photo Credit: Scott Eliason
  • Global Rank: G1 - Critically Imperiled
  • Legal Status: Federally Endangered
  • Family: Brassicaceae
  • State: CA
  • Nature Serve ID: 130408
  • Date Inducted in National Collection:

Thelypodium stenopetalum is a biennual herb in the mustard family (Brassicaceae) endemic to the San Bernardino Mountains, San Bernardino County, California. This species has linear shaped lavender petals that bloom between March and August. The flowering stems are not produced until the second or third year of growth (CNPS 2007). Thelypodium stenopetalum was listed as endangered in 1998. Two occurrences have been extirpated and the eight remaining occurrences at the southwest end of Erwin Lake and the southwest end of Big Bear Lake have not been documented recently and have either been degraded or extirpated.

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  • 09/01/2020
  • Orthodox Seed Banking

Based on an September 2020 extract of the California Plant Rescue Database, California Botanic Garden holds 4 accessions of Thelypodium stenopetalum in orthodox seed collection. There are as many as 19471 seeds of this species in their collection - although some may have been used for curation testing or sent to back up.

Nature Serve Biotics
  • 05/02/2017

Endemic to California, Thelypodium stenopetalum is known from 10 total, and perhaps as few as 3 or 4 extant, occurrences in the meadows of Big Bear Basin in San Bernardino County. It is protected in part at Baldwin Lake Ecological Reserve. Seriously threatened by urbanization, ORVs, weeds, grazing and burros. Ownership is a mix of USFS, DFG, Private and City lands.

Naomi Fraga
  • 01/01/2010

Thelypodium stenopetalum populations are subject to several impacts leading to destruction, alteration and fragmentation of habitat. Threats include: Alteration of hydrologic regimes Unauthorized livestock grazing Recreation activities

Naomi Fraga
  • 01/01/2010

Thelypodium stenopetalum exhibits high variation in population size based on conditions related to climate. This species is more abundant in years with above average rainfall (USDA FS 2007).

Naomi Fraga
  • 01/01/2010

Little is known about the biology and ecology of T. stenopetalum.

Naomi Fraga
  • 01/01/2010

A recovery plan for T.stenopetalum was approved in July 1998 (USFWS 1998). The recovery plan identifies criteria for downlisting T. stenopetalum and recovery tasks that could include San Bernardino National Forest management or cooperation and/or National Forest System lands.The following list of conservation practices should be considered for T. stenopetalum: Continue implementation of the 1998 recovery plan for T. stenopetalum, and the revised Recovery Plan when completed. Implement actions in the SBNF Meadow Habitat Management Guide. Continue to monitor fence lines and signing that protects populations and reconstruct in a timely manner as necessary. Work with adjacent landowners to reduce effects of unclassified trail use on NFS lands. Survey all new occurrences of T. stenopetalum and any occurrences that have not been visited in the past ten years, and record occurrence status, habitat condition, and threats. Apply the habitat suitability criteria and detection protocol developed for this taxon to surveys at the project level. Collect a herbarium voucher specimen of T. stenopetalum to document new occurrences or to verify a historical occurrence if the occurrence is not known to have been documented in at least ten years prior.

Naomi Fraga
  • 01/01/2010

San Bernardino National Forest occasionally performs surveys for this species; according to the Habitat Management Guide populations should be monitored every ten years.

Naomi Fraga
  • 01/01/2010

Establish and maintain a genetically representative seed bank.


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Taxon Thelypodium stenopetalum
Authority S. Watson
Family Brassicaceae
CPC Number 4279
ITIS 23413
Common Names Slender-petaled Mustard | slenderpetal thelypody
Associated Scientific Names Thelypodium stenopetalum | Thelypodiopsis stenopetala
Distribution Thelypodium stenopetalum is endemic to the San Bernardino Mountains, San Bernardino County California. The California Natural Diversity Database reports 10 occurrences in Big Bear, and Holcomb valley
State Rank
State State Rank
California S1

Thelypodium stenopetalum occurs in vernally wet meadows, alkaline flats, and lakeshores at elevations of 6,470-7,430 ft (2,054-2,237 m). Plants of this species tend to occupy drier sites within meadows in areas dominated by sagebrush scrub. Artemisia nova and Iris missouriensis are often associated with this species. It appears that there is greater germination close to the base of Artemisia shrubs (USDA FS 2007). Thelypodium stenopetalum is associated with vernally wet alkaline clay soils.

Ecological Relationships

Thelypodium stenopetalum is a larval host plant for the rare Andrews marble butterfly (Euchloe hyantis andrewsi). Eggs are laid at the tip of the flower stalk, and the larvae feed on the upper fruit stalks. At the North Baldwin Lake occurrence, up to 20% of Thelypodium plants showed insect damage.

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

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