Arctotheca calendula (L.) Levyns (Capeweed)

California Plant Pest Rating
Arctotheca calendula (L.) Levyns (Capeweed)
Asterales; Asteraceae
Pest Rating: A  |    Proposed Seed Rating: P

Initiating Event:

This plant was  listed as a noxious weed in California in 2010 (Invasive species compendium- CABI).

History & Status:

Capeweed is a Rosette-forming winter annual, up to 30 cm tall. It has typical daisy flowers heads with dark purple disk flowers and yellow ray flowers. Plants typically colonize open sites with exposed soils. Capeweed is introduced from South Africa, but it is also common in Australia, where it is an abundant pasture weed. Certain capeweed populations in Australia have developed resistance to bipyridylium herbicides. Handling plants can cause contact dermatitis in sensitive individuals. Capeweed has proven invasive in horse pastures and vineyards where taller, more palatable vegetation is removed. There has been much confusion between capeweed and prostrate capeweed (A. prostrata). Prostrate capeweed is a common groundcover perennial sold in flats in nurseries in mild areas of California. Prostrate capeweed can be locally invasive where it has been planted, as it actively spreads to form patches vegetatively. However, it does not form seeds in California; perhaps there is only one self-incompatible clone in cultivation at this time.

Official Control: Capeweed has been recognized as a harmful organism in Brazil, Colombia and Peru. It has naturalized in Australia, New Zealand and other countries in Asia, Africa, South America and Europe.        

California Distribution: Capeweed may have arrived in California in a shipment of grass seed from Australia, where it is a common weed.  Because of taxonomic confusion with prostrate capeweed, the range of capeweed is somewhat ambiguous. It has been reported in Alameda*, Amador, Humboldt*, Los Angeles, Mendocino, Monterey*, Marin*, Merced*, Sacramento, Santa Barbara, Santa Cruz*, San Francisco, San Luis Obispo, San Mateo*, Sonoma, Stanislaus* and Yolo Counties (Cal Flora Databse: Distribution by county: Arctotheca calendula  (L.) Levyns Cape weed). Asterixed county reports are supported by confirmed, identified vouchers.

California Interceptions: 11 vouchers have been submitted to CDFA for identification between 2000 and 2015 (Pest and Damage Report Database).

International: Capeweed  is native to South Africa. It is reported as naturalized in central Portugal and southwestern Spain, southern Portugal, New Zealand and as an environmental weed in Australia. (Lazarides and Hince, 1993 ). Capeweed has been raised as an ornamental in England since the mid-18th century (USDA APHIS Pest Risk Assessment).

Habitat: Capeweed prefers sandy, well drained soil, sand dunes,steam banks and rocky outcrops. It is used as a groundcover (Joffe, 2001). It does not thrive on soils low in potassium and high in salt. Areas on light textured soils devoid of vegetation during late summer /autumn are most likely to become infested with capeweed (Department of Primary Industries, Water and Environment , Tasmania, 2002). As it is avoided by livestock, it can spread quickly in horse pastures.

This risk capeweed would pose to California is evaluated below:

Consequences of Introduction:

1) Climate/Host Interaction: Risk is High (3), as this plant is naturalized along the coast of California and at five inland sites in the San Joaquin/Sacramento region. (Cal Flora Databse: Distribution by county: Arctotheca calendula (L.) Levyns: Cape weed).

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

Score: 3

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) Pest Host Range:  Risk is High (3) as weeds do not require any one host, but grow wherever ecological conditions are favorable.

Evaluate the host range of the pest:

Score: 3

– 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: Risk is High (3). Capeweed has both high reproduction potential and highly mobile propagules. The plant reproduces via seeds. One plant can spawn a population spreading to cover up to 200 square feet in one to two years (Mathias, 1982; CDFA , 2002). Capeweed stem pieces with nodes can spread to new location by heavy equipment (Bossard, et al. 2002). Dispersal can be aided by wind or in contaminated soil. (Miles, 2002) Human activity and animals also aid in spread of seeds and rooted stolons (Wood 1994).

Evaluate the dispersal potential of the pest:

Score: 3

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: Risk is High (3) as capeweed can become a troublesome weed in pastures, crops and home gardens in California. It can smother grasses and clover seedlings in newly sown pastures in the state. Capeweed can dominate overgrazed pastures in drier regions of California and can die off during summer, leaving bare areas vulnerable to invasion by other weeds.

It invades disturbed soil along roadsides and in crops. Capeweed can cause poisoning in livestock, if they consume it. Seeds can become embedded in wool. This can result in reduced yields. It reduces the value of stock by lowering their weight. Capeweed does not provide continous ground cover and feed value over summers  (APHIS Weed Risk Assesment).

Evaluate the economic impact of the pest to California using these criteria:

Economic Impact: A, B, 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 by other states or countries)

D. The pest could negatively change normal production 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 use

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: Risk is High (3) in California. Capeweed disrupts natural grassland communities that are grazed, invades native habitat along the coast including coastal prairie, and triggers additional treatment to control it. In desert areas of California, Capeweed can increase the risk of soil erosion as its mature plants dry up and break quickly, leaving no cover over summer. It can also threaten native plant communities in Califorinia by crowding out grasses, herbs and small herbs (Bossard et al., 2000). Capeweed can cause hay fever and handling plants can cause contact dermatitis in sensitive people (CDFA 2002). It can escape into lawns and adjacent planting areas in California (Perry, 1992). Since there are no registered biological agents for Capeweed control, additional private or official treatments may be needed for its control ( CDFA 2002).

Evaluate the environmental impact of the pest on California using the following criteria:

Environmental Impact: A, C, 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. Significantly impacting cultural practices, home/urban gardening or ornamental plantings.

Score the pest for Environmental Impact:

Environmental Impact Score: 3

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 capeweed:

Add up the total score and include it here:

Low = 5-8 points

Medium = 9-12 points

High = 13-15 points

Total points based on above criteria: High (15).

6) Post Entry Distribution and Survey Information:
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:

Score: Medium (–2)

-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: (13).


Capeweed has naturalized in coastal and some inland areas of Northern California. There is confusion as to whether reports refer to capeweed or prostrate capeweed. Nevertheless, it has the potential to get widely established in desert areas and  grazed pastures. There is little uncertainty as to whether this plant can establish widely in CA, as it has establsihed in CA and has spread widely in silmilar habitats in Australia.

Conclusion and Rating Justification:

Proposed Rating: based on the score listed above the pest is a high risk. Because it has spread in certain areas of northern california and has a good potential to widely spread in the state, an A rating would be justifed. Because it can spread in grass seed, it should be prohibited from seed for planting.


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.

Bossard, C.C., J.M. Randall, and M.C. Hoshovsky. 2000. Invasive Plants of California Wildlands. pp.49-53. University of California Press.

California Department of Food and Agriculture (CDFA) Encycloweedia Homepage. 2002. Notes on Identification, Biology, and Management of Plants defined as Noxious Weeds by California Law.

Cal Flora Databse: Distribution by county: Arctotheca calendula  (L.) Levyns


Consortium of California Herbaria ( 2014.

Department of Primary Industries, Water and Environment, Tasmania website: Weed Service Sheet 128 – Arctotheca calendula. 2002.

Environmental weeds of Australia for Biosecurity Queensland : Arctotheca Calendula– Factsheet

Fairnie, I.J. Nitrite poisoning in sheep due to capeweed (Arctotheca calandula). Australian Veterinary Journal 1969, February; 45(2): 78-9.

Invasive species compendium: Arctotheca calendula (Capeweed): Accessed 11/9/2016

Lazarides, M. and B. Hince, editors. 1993. CSIRO handbook of economic plants of Australia. P. 24. CSIRO, Victoria, Australia

Lehtonen, Polly, USDA-APHIS PPQ Biological and Technical Services: Weed Risk Assesment  for Arctotheca calendula (L.) Levyns; Accessed 11/9/2016

Mahoney, A. M. & R. J. McKenzie. 2008. Notes On Two Southern African Arctotis Species (Arctotideae: Asteraceae) Growing In California. Madroño 55: 244–247.

Mathias, M. E., editor. 1982. Flowering Plants in the Landscape. University of California Press. p. 139

Miles, J. 2002. Capeweed (Arctotheca calendula) weed fact sheet, Eurobodalla Shire Council, New South Wales, Australia, South Coast Weeds website. Accessed 11/9/2016

Perry, B. 1992. Landscape Plants for Western Regions, an illustrated guide to plants for water conservation. Claremont CA: Land Design Pub. pp. 94, 125-126.

Pest and Damage Record Database; Plant Health and Pest Prevention Services, California Department of Food and Agriculture. Accessed on 11/9/2016

Pethick D.W., Chapman, H.M. The effect of Arctotheca calendula (capeweed) on digestive function of sheep. Australian Veterinary Journal 1991 Nov.; 68(11): 361-3

Weed Identification in Australia: Capeweed

Wood, H. 1994. The introduction and spread of Capeweed, Arctotheca calendula (L.)Levyns (Asteraceae) in Australia. Plant Protection Quarterly 9, 2-8.

Responsible Party:

Raj Randhawa, Senior Environmental Scientist; Dean G. Kelch, Primary Botanist; California Department of Food and Agriculture; 1220 N Street, Sacramento, CA 95814; Tel. (916) 654-0312;[@]

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Pest Rating: A  |    Proposed Seed Rating: P

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