Plant Assessment Form

Carrichtera annua

Synonyms: Vella annua

Common Names: Ward's weed

Evaluated on: 21-Dec-16

List committee review date: 26/01/2017

Re-evaluation date:


Lynn Sweet/Associate Research Specialist
University of California, Riverside
75-080 Frank Sinatra Dr., Palm Desert, CA 92211

List committee members

Jutta Burger
Naomi Fraga
Denise Knapp
Chris McDonald
Ron Vanderhoff
John Knapp
Elizabeth Brusati

General Comments

Information used to prepare the PAF should be based on "ecological impacts on the species' behavior in ecosystems within the state; however, species behavior elsewhere within similar ecosystems can be used when a non-native species previously unknown within a state is newly discovered and requires judgement as to whether it qualifies for rapid response (Criteria for Categorizing Invasive Non-Native Plants that Threaten Wildlands)." This is the case with Carrichtera annua in California since it was first documented as occurring in natural areas here in 2007 and has not yet spread widely, but is considered invasive in Australia.

Table 2. Criteria, Section, and Overall Scores

Overall Score? Moderate
Alert Status? Alert
Documentation? 3.5 out of 5
Score Documentation
1.1 ?Impact on abiotic ecosystem processes C. Minor Other Published Material
Four-part score CBCD Total Score
1.2 ?Impact on plant community B. Moderate Other Published Material
1.3 ?Impact on higher trophic levels C. Minor Reviewed Scientific Publication
1.4 ?Impact on genetic integrity D. None Reviewed Scientific Publication
2.1 ?Role of anthropogenic and natural disturbance in establishment B. Moderate Reviewed Scientific Publication
Total Points
13 Total Score B
2.2 ?Local rate of spread with no management B. Increases less rapidly Reviewed Scientific Publication
2.3 ?Recent trend in total area infested within state B. Increasing less rapidly Other Published Material
2.4 ?Innate reproductive potential
(see Worksheet A)
B. Moderate Reviewed Scientific Publication
2.5 ?Potential for human-caused dispersal B. Moderate Reviewed Scientific Publication
2.6 ? Potential for natural long-distance dispersal C. Rare Reviewed Scientific Publication
2.7 ?Other regions invaded B. Invades 1 or 2 ecological types Reviewed Scientific Publication
3.1 ?Ecological amplitude/Range
(see Worksheet C)
C. Limited Other Published Material
Total Score C
3.2 ?Distribution/Peak frequency
(see Worksheet C)
D. Very low Observational

Table 3. Documentation

Scores are explained in the "Criteria for Categorizing Invasive Non-Native Plants that Threaten Wildlands".

Section 1: Impact
Question 1.1 Impact on abiotic ecosystem processes? C Other Published Material
Identify ecosystem processes impacted:

Soil erosion- Replacement of native stands in dense patches, however, it is an annual plant, and so may leave bare patches that are exposed to soil erosion (Cook 2003). Moderate probability of large scale soil movement. (1)

Fire regime change low- Noted to persist as dry biomass following senescence, however, this was judged to be of minor concern. (2)

Sources of information:

(1) Victorian Weed Risk Assessment (WRA)
(2) Cooke, Ash, & Groves (2003)

Question 1.2 Impact on plant community composition,
structure, and interactions?
B Other Published Material
Identify type of impact or alteration:

Competition with native plants: C. annua forms dense stands, and displaces native plants and other weed species. It can comprise up to an estimated 95% of total herbaceous biomass (1). Direct replacement of biomass by invader (Victoria, Australia weed risk assessment). (2)
Harris and Facelli (2003) did not find impacts on native species abundance in experimentally-manipulated densities of C. annua, however, this finding may have been due to the densities used in the experiment (too low) or may have been community-specific, where the native species chosen were segregated in life history/resource capture (native arid chenopod shrublands, Australia). (3)

In the US, in San Diego County, it was assessed to be a serious threat on specific soils "that hold still relatively common sensitive forbs like Pentachaeta, Harpagonella, Microseris, and Convolvulus, not to mention Acanthomintha and other clay obligates."(4)

Several other species in the Brassicaceae do not have mycorrhyzal associates and also leach compounds which tend to inhibit growth of mycorryzal hyphae, thereby effectively sterilizing a soil of fungal symbionts. It is possible that this species does the same (5) (6).

Sources of information:

(1) Cooke, Ash, & Groves (2003)
(2) Victorian Weed Risk Assessment (WRA)
(3) Harris & Facelli (2003)
(4) McConnell, personal communication (2017)
(5) Wixted and McGraw 2010
(6) Bell and Muller 1973

Question 1.3 Impact on higher trophic levels? C Reviewed Scientific Publication
Identify type of impact or alteration:

Unpalatable to livestock and therefore significantly reduces productivity of grazing areas (1,2).
Prolific seeds that are dropped into the soil are fed upon by ants, potentially increasing locally available food for them (Cooke et al. 2013), however, there is no documented change or higher-level impact from this. (3)

Sources of information:

(1) Victorian Weed Risk Assessment (WRA)
(2) Cooke, Ash, & Groves (2003)
(3) Cooke, Ash, & Groves (2013)

Question 1.4 Impact on genetic integrity? D Reviewed Scientific Publication

C. annua is in the Brassicaceae (mustard) family. There are no other Carrichtera species noted to be in California. (1)
This species is most closely related to genera in the monophyletic group, Vellinae, containing Vella, Carrichtera, and Orychophragmus, and of this group, this is the only species in California. (2)
While there are many other mustard species, native, non-native, and crop plants, present in California, it is unknown if C. annua can successfully cross with species in other phylogenenetic groups within Brassicaceae, but may be unlikely.

Sources of information:

(1) Calflora (accessed 12/30/16)
(2) Bailey et al. (2006)

Section 2: Invasiveness
Question 2.1 Role of anthropogenic and natural disturbance
in establishment?
B Reviewed Scientific Publication
Describe role of disturbance:

C. annua germination may be reduced by litter from other species (e.g. Casuarina trees), and less plants were found here than in open areas, however, germination may still occur under moderate canopy (1).

According to Cooke and others (2003), the species is known to invade disturbed and over-grazed sites, and thus is increased by disturbance. However, this evidence and the Victorian weed risk assessment indicate that this plant does not seem to require disturbance to invade. (2,3)

Sources of information:

(1) Barritt & Facelli (2001)
(2) Cooke, Ash, & Groves (2003)
(3) Victorian Weed Risk Assessment (WRA)

Question 2.2 Local rate of spread with no management? B Reviewed Scientific Publication
Describe rate of spread:

In Australia, the plant was likely introduced to a single site, showed a lag phase of 30 years (possibly due to edaphic factors), and then has rapidly spread in that region (1). These authors believe that the specIes has reached climatic limits in just under a century due to rapid spread and some long-distance dispersal by humans (vehicle and stock movements, railways, noted in Cooke et al. 2003) (2). Local spread of its prolific seed output may be facilitated by ant species, while long-distance dispersal could be via vertebrate mammals (2). No source notes specific rate of spread, making this difficult to answer with certainty, however, the rate of spread within Australia, identified vectors, as well as local dominance indicate that it may increase rapidly.
In California, noted from monitoring a mapped population in the La Costa Carlsbad (San Diego County) area that it has infested a rather large area in a short amount of time. (3)

Sources of information:

(1) Cooke, Groves, & Ash (2011)
(2) Cooke, Ash, & Groves (2003)
(3) Giessow, J. (pers. comm. 1/1/17)

Question 2.3 Recent trend in total area infested within state? B Other Published Material
Describe trend:

This species was first noted in Monterey in 1979, and not noted in San Diego County much prior to 2007 (1).
There are currently two sites in southern CA: Camp Pendleton MCB and a preserve in Carlsbad (two populations, Rancho La Costa HCA), both of which are under treatment. Since the known locations are being treated the question is scored as "B: Increasing less rapidly." (2,3)

Sources of information:

(1) Vinje (2008)
(2) Giessow, J. (pers. comm. 1/1/17)
(3) San Diego MMP Plant Assessment Form 2011

Question 2.4 Innate reproductive potential? B Reviewed Scientific Publication
Describe key reproductive characteristics:

Noted to have both a soil seedbank and an aerial seedbank on the standing dead matter that is less susceptible to invertebrate predation, but more susceptible to fire and other above-ground disturbance . Longevity in the soil is uknown but thought to be short. Local persistence is therefore explained by the dual banking strategy (1,2).

Sources of information:

(1) Meissner & Facelli (1999)
(2) Cooke, Ash, & Groves (2003)

Question 2.5 Potential for human-caused dispersal? B Reviewed Scientific Publication
Identify dispersal mechanisms:

They may be dispersed longer distances by vehicles, on larger animals and clothing, and in contaminated agricultural produce (1). As well accidental, infrequent long-distance dispersal via vehicles and railways was noted noted in Cooke (2). In California, managers of the population in Carlsbad believe seed was introduced via erosion control devices (silt fencing) when the developer on the adjacent parcel was creating house pads (3).

Sources of information:

(1) Weeds of Australia: Biosecurity Queensland Edition (accessed 12/30/16)
(2) Cooke, Ash, & Groves (2003)
(3) Vinje 2011

Question 2.6 Potential for natural long-distance dispersal? C Reviewed Scientific Publication
Identify dispersal mechanisms:

Dispersal mechanisms are thought to be primarily local- ants, gravity and water. The plant has no adaptation for wind dispersal. The species has some limited water dispersal adaptation (1) due to a mucilaginous seed coat, however, this is not a long-distance dispersal mechanism. Possible long-distance dispersal via emu, or other vertebrate species in Australia has been suggested, but not documented (2).

Sources of information:

(1) Gutterman, Yitzchak & Shem-Tov (1997)
(2) Cooke, Ash, & Groves (2003)

Question 2.7 Other regions invaded? B Reviewed Scientific Publication
Identify other regions:

Native to Southern Europe, Mediterranean Islands, and Northern Africa.(1)
Serious weed of semi-arid rangelands in Australia, where it is a significant environmental weed in Victoria, South Australia and Western Australia. (3)
Noted as present in types in Australia: native arid chenopod shrublands Australia specifically (4,5,6), as well as "rangelands, grasslands, open woodlands, pastures, disturbed sites, and waste areas in semi-arid regions."(3)
Listed in Victoria risk assessment as being present in: Semi-arid woodland, Shrubby Woodland. New types that may be invaded by this species in California based on this information: chenopod scrub, and open woodland. (7)

Sources of information:

(1) GBIF (Accessed 12/26/16)
(2) Cooke et al. 2011
(3) Weeds of Australia Biosecurity Queensland Edition (accessed 12/30/16))
(4) Harris & Facelli (2003)
(5) Meissner & Facelli (1999)
(6) Facelli & Chesson (2008)
(7) Victorian Weed Risk Assessment (WRA)

Section 3: Distribution
Question 3.1 Ecological amplitude/Range? C Other Published Material

This species was first noted in Monterey in 1979, and was not noted in San Diego County much prior to 2007 (1).
Two geolocated observations of C. annua are listed on the Consortium of California Herbaria website, out of 12 total observations. The earliest specimens are from 2007, and the latest 2016, all from San Diego County (2).
The Plant Assessment Form from the San Diego MMP lists non-native grassland and Diegan Coastal Sage Scrub. Chaparral has also been noted as a community type it occurs in. (3)
In Carlsbad, this plant was located on a southern-facing slope growing among open Diegan coastal sage scrub dominated by California sage (Artemisia californica). Associates included coast sunflower (Encelia californica), buckwheat (Eriogonum fasciculatum), lemonade berry (Rhus integrifolia), and tocalote (Centaurea melitensis). C. annua was growing on open clay lenses in the coastal sage scrub and underneath the shrubs. Although vernal pool affiliates were noted on consortium specimens, observational evidence suggests: "This plant thrives in open areas, including scrub understory. It does not like long term inundation and competes poorly with dense herbaceous cover." (4)

Sources of information:

(1) Vinje 2008
(2) Consortium of California Herbaria (accessed 12/30/16)
(3) San Diego MMP Plant Assessment Form 2011
(4) J. Giessow, personal communication (1/4/17)

Question 3.2 Distribution/Peak frequency? D Observational
Describe distribution:

This species has only been documented in San Diego County, near the coastline, in the La Costa Carlsbad area and at Camp Pendleton (1). It is present but not >5% in coastal sage scrub and bluff, and chaparral (1,2).

Sources of information:

(1) Consortium of California Herbaria (accessed 12/30/16)
(2) J. Giessow, personal communication (1/4/17)

Worksheet A - Innate reproductive potential

Reaches reproductive maturity in 2 years or less Yes
Dense infestations produce >1,000 viable seed per square meter Yes
Populations of this species produce seeds every year. Yes
Seed production sustained over 3 or more months within a population annually No
Seeds remain viable in soil for three or more years Unknown
Viable seed produced with both self-pollination and cross-pollination Yes
Has quickly spreading vegetative structures (rhizomes, roots, etc.) that may root at nodes No
Fragments easily and fragments can become established elsewhere No
Resprouts readily when cut, grazed, or burned No
Total points: 5
Total unknowns: 1
Total score: B?

Related traits:

Noted to have both a soil seedbank and an aerial seedbank on the standing dead matter.

Worksheet B - Arizona Ecological Types is not included here

Worksheet C - California Ecological Types

(sensu Holland 1986)
Major Ecological Types Minor Ecological Types Code?
Marine Systemsmarine systems
Freshwater and Estuarine lakes, ponds, reservoirs
Aquatic Systemsrivers, streams, canals
Scrub and Chaparralcoastal bluff scrubD, < 5%
coastal scrubD, < 5%
Sonoran desert scrub
Mojavean desert scrub (incl. Joshua tree woodland)
Great Basin scrub
chenopod scrub
montane dwarf scrub
Upper Sonoran subshrub scrub
chaparralD, < 5%
Grasslands, Vernal Pools, Meadows, and other Herb Communitiescoastal prairie
valley and foothill grassland
Great Basin grassland
vernal pool
meadow and seep
alkali playa
pebble plain
Bog and Marshbog and fen
marsh and swamp
Riparian and Bottomland habitatriparian forest
riparian woodland
riparian scrub (incl.desert washes)
Woodlandcismontane woodland
piñon and juniper woodland
Sonoran thorn woodland
Forestbroadleaved upland forest
North Coast coniferous forest
closed cone coniferous forest
lower montane coniferous forest
upper montane coniferous forest
subalpine coniferous forest
Alpine Habitatsalpine boulder and rock field
alpine dwarf scrub
Amplitude (breadth): C
Distribution (highest score): D

Infested Jepson Regions

Click here for a map of Jepson regions

  • Southwest