Jeweled distaff thistle | Carthamus oxyacantha

Jewel distaff thistle (photo by Steve Hurst, hosted by the USDA-NRCS PLANTS Database)
Jewel distaff thistle (photo by Steve Hurst, hosted by the USDA-NRCS PLANTS Database)
California Pest Rating for
Jeweled distaff thistle | Carthamus oxyacantha
Family:  Asteraceae
Pest Rating: B | Proposed Seed Rating: P

 Initiating Event:

Jeweled distaff thistle was reported in California in the late 1970’s and had no previous pest rating. A pest rating proposal is required to determine a permanent rating for this pest.

History & Status:

Background: Jeweled distaff thistle is a spiny-leaved annual weed that can grow up to 1.5 m tall. Like other spiny plants in the genus Carthamus, this species is not eaten by livestock, enabling it to spread on grazing lands2. The yellow flowers are born in flower heads approximately two to three cm in diameter and the leaves are covered with spines. It is a wild safflower relative found in arid and semi-arid environments in central and southern Asia5. It was collected in 1978 in Monterey County, California. It is considered by the United States Department of Food and Agriculture to be a noxious weed subject to eradication if found. Jeweled distaff thistle is a pernicious weed of agricultural lands especially, it reduces the yield of cereal crops. Jeweled distaff thistle most closely resembles cultivated safflower; it has smaller heads and much spinier leaves1.

Worldwide Distribution: Jeweled distaff thistle is reported from Afghanistan, India, Iran, Iraq, Saudi Arabia, Syria, Kyrgyzstan, Uzbekistan, Pakistan, Azerbaijan, Armenia, Tajikistan and Turkmenistan4.

California Distribution:  It was reported only in Monterey County, where it may be eradicated.

Official Control: Jeweled distaff thistle is listed as a harmful organism in

Colombia, Honduras and Mexico6. It is listed by U.S. Federal government as Noxious weed in Florida, Minnesota South Carolina, Massachusetts and Class

“A” Noxious weed for Alabama, North Carolina and Vermont7.

California Interceptions: Historically, only two vouchers were submitted in 1978 from Monterey County3.

The risk Carthamus oxyacantha (Jeweled distaff thistle) would pose to California is evaluated below.

Consequences of Introduction:

1) Climate/Host Interaction: Jeweled distaff thistle is adapted to central and southern Asia and similar climates. It may able to establish in a larger but limited part of California like Carthamus tinctorius. It receives a Medium (2) in this category.

Evaluate if the pest would have suitable hosts and climate to establish in California:

Low (1) Not likely to establish in California; or likely to establish in very limited areas.

Medium (2) may be able to establish in a larger but limited part of California.

High (3) likely to establish a widespread distribution in California.

2) Known Pest Host Range: Jeweled distaff thistle do not require any one host, but grow wherever ecological conditions are favorable. It receives a High (3) in this category.

Evaluate the host range of the pest.

Low (1) has a very limited host range

Medium (2) has a moderate host range

High (3) has a wide host range

3) Pest Dispersal Potential: Jeweled distaff thistle reproduces only by seed; each plant can produce up to 36 flower head that produces 15 to 20 single-seeded fruits5. These flower heads are dispersed short distances by foraging animals, human activity or by wind. They may be dispersed longer distances by vehicles, on larger animals and in contaminated agricultural produce. It receives a Medium (2) in this category

Evaluate the natural and artificial dispersal potential of the pest.

Low (1) does not have high reproductive or dispersal potential.

Medium (2) has either high reproductive or dispersal potential.

High (3) has both high reproduction and dispersal potential.

4) Economic Impact: Jeweled distaff thistle could invade crops, especially summer season crops in California. It could decrease crop yield and can lower the crop value, as it has been reported in its native range. Where adapted it displaces both native plants and other plants; this could negatively change normal cultural practices. It had spiny-tipped leaves with phyllaries heads which could injured the agriculturally important animals.  It receives a High (3) in this category.

Evaluate the economic impact of the pest to California using the criteria below.

Economic Impact: A, B, D, F

A. The pest could lower crop yield.

B. The pest could lower crop value (includes increasing crop production costs).

C. The pest could trigger the loss of markets (includes quarantines).

D. The pest could negatively change normal cultural practices.

E. The pest can vector, or is vectored, by another pestiferous organism.

F. The organism is injurious or poisonous to agriculturally important animals.

G. The organism can interfere with the delivery or supply of water for agricultural uses.

Economic Impact Score: 3

Low (1) causes 0 or 1 of these impacts.

Medium (2) causes 2 of these impacts.

High (3) causes 3 or more of these impacts.

5) Environmental Impact: Jeweled distaff thistle has not yet spread widely in California. If it does spread, it might trigger new chemical treatments by ranchers and land managers. It receives a Medium (2) in this category.

Evaluate the environmental impact of the pest on California using the criteria below.

Environmental Impact:  D

A. The pest could have a significant environmental impact such as lowering biodiversity, disrupting natural communities, or changing ecosystem processes.

B. The pest could directly affect threatened or endangered species.

C. The pest could impact threatened or endangered species by disrupting critical habitats.

D. The pest could trigger additional official or private treatment programs.

E. The pest significantly impacts cultural practices, home/urban gardening or ornamental plantings.

Environmental Impact Score: 2

Low (1) causes none of the above to occur.

Medium (2) causes one of the above to occur.

High (3) causes two or more of the above to occur.

Consequences of Introduction to California for Carthamus oxyacantha (Jeweled distaff thistle): Medium (12)

Low = 5-8 points

Medium = 9-12 points

High = 13-15 points

6) Post Entry Distribution and Survey Information: Jeweled distaff thistle has been reported only in Monterey County and seems likely eradicated in this area. It receives a Low (-1) in this category.

Evaluate the known distribution in California. Only official records identified by a taxonomic expert and supported by voucher specimens deposited in natural history collections should be considered. Pest incursions that have been eradicated, are under eradication, or have been delimited with no further detections should not be included:

Not established (0) Pest never detected in California, or known only from incursions.

Low (-1) Pest has a localized distribution in California, or is established in one suitable climate/host area (region).

Medium (-2) Pest is widespread in California but not fully established in the endangered area, or pest established in two contiguous suitable climate/host areas.

High (-3) Pest has fully established in the endangered area, or pest is reported in more than two contiguous or non-contiguous suitable climate/host areas.

Final Score:

The final score is the consequences of introduction score minus the post entry distribution and survey information score: Medium (11)


Jeweled distaff thistle has been known in California for decades, although it has not yet spread widely, there is nothing to stop it spreading in the appropriate habitats. There is some uncertainty as to how well it can spread in California if it escapes.

Conclusion and Rating Justification:

Conclusions of the harm(s) associated with this pest to California using all of the evidence presented above: Proposed Rating: based on the score listed above the pest is a medium risk weed with a distribution in Monterey County. A B” rating is recommended, as the plant is invasive and is a federal noxious weed.

  1. Flora of North America  online   Accessed April 26, 2017.
  2. Federal Noxious Weed Dissminules of U.S. Accessed May 9, 2017.
  3. Baldwin, B. G., D. H. Goldman, D. J. Keil, R. Patterson, T. J. Rosatti, and D. H. Wilken, editors. 2012. The Jepson manual: vascular plants of California, second edition. University of California Press, Berkeley. Accessed May 9, 2017.
  4. US National Plant Germplasm system. Accessed May 9, 2017.
  5. Sullaiman Mohammed, Mohammad A Fredan 2015, American Journal of Environmental Sciences. Accessed May 9, 2017.
  6. USDA Phytosanitary Certificate Issuance & Tracking System (PCIT) Phytosanitary Export Database (PExD). Accessed May 9, 2017
  7. USDA  Natural Resouces Conservation Services online. Accessed May 9, 2017

Responsible Party:

Javaid Iqbal,  California Department of Food and Agriculture; 1220 N Street, Sacramento, CA 95814; Tel. (916) 403-6695;[@]


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Pest Rating: B | Proposed Seed Rating: P

Posted by ls

2 thoughts on “Jeweled distaff thistle | Carthamus oxyacantha”

  1. The jeweled distaff thistle detections in Monterey County were in a vacant lot behind the Schilling McCormick Company where they used to dump their mill waste. The lot has long since been paved over and built on. When I was Staff Biologist for Monterey County we checked the fringes of the lots and did not see any more unusual plants. The Schilling Company is no longer processing spices at that location.

    1. Thank you for confirmation that it is indeed eradicated at the only known locality in CA.

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