Plant Assessment Form

Chondrilla juncea

Common Names: skeleton weed; devil's grass; hogbite; gum succory; naked weed

Evaluated on: 2/8/05

List committee review date: 08/07/2005

Re-evaluation date:

Evaluator(s)

Elizabeth Brusati, project manager
California Invasive Plant Council
1442A Walnut St. #462, Berkeley, CA 94709
510-843-3902
edbrusati@cal-ipc.org
Joseph M. DiTomaso
University of California, Davis
Dept. Plant Sci., Mail Stop 4, Davis, CA 95616
530-754-8715
jmditomaso@ucdavis.edu

List commitee members

Jake Sigg
Peter Warner
Bob Case
John Knapp
Elizabeth Brusati

General Comments

No general comments for this species

Table 2. Criteria, Section, and Overall Scores

Overall Score? Moderate
Alert Status? No Alert
Documentation? 3 out of 5
Score Documentation
1.1 ?Impact on abiotic ecosystem processes B Reviewed Scientific Publication
Impact?
Four-part score BBUD Total Score
B
1.2 ?Impact on plant community B. Moderate Reviewed Scientific Publication
1.3 ?Impact on higher trophic levels U. Unknown
1.4 ?Impact on genetic integrity D. None Other Published Material
2.1 ?Role of anthropogenic and natural disturbance in establishment B. Moderate Reviewed Scientific Publication
Invasiveness?
Total Points
15 Total Score B
2.2 ?Local rate of spread with no management B. Increases less rapidly Observational
2.3 ?Recent trend in total area infested within state B. Increasing less rapidly Observational
2.4 ?Innate reproductive potential
(see Worksheet A)
A. High Reviewed Scientific Publication
2.5 ?Potential for human-caused dispersal B. Moderate Reviewed Scientific Publication
2.6 ? Potential for natural long-distance dispersal B. Occasional Reviewed Scientific Publication
2.7 ?Other regions invaded B. Invades 1 or 2 ecological types Other Published Material
3.1 ?Ecological amplitude/Range
(see Worksheet C)
A. Widespread Other Published Material
Distribution?
Total Score B
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? B Reviewed Scientific Publication
Identify ecosystem processes impacted:

Reduces soil nitrogen. Strong competitor for nitrogen. C. juncea is capable of reducing the level of nitrogen by the equivalent of 56kg/ha of artificial nitrogen.


Sources of information:

1. Panetta, F. D. and J. Dodd 1987. The biology of Australian weeds. 16. Chondrilla juncea L. Journal of the Australian Institute of Agricultural Science 53(2): 83-95
2. Liao, J. D., S. B. Monsen, V. J. Anderson, and N. L. Shaw. 2000. Seed biology of rush skeletonweed in sagebrush steppe. Journal of Range Management 53(5): 544-549.


Question 1.2 Impact on plant community composition,
structure, and interactions?
B Reviewed Scientific Publication
Identify type of impact or alteration:

Outcompetes other plants for nitrogen and other nutrients (1, 2). Grows in dense monocultures in other western states, but has not reached this level of density in California (2). Dense near Folsom Dam and in three or four counties (3). Presence of seedlings and young plants reduce seed mortality of Chondrilla (1).


Sources of information:

1. Panetta, F. D. and J. Dodd 1987. The biology of Australian weeds. 16. Chondrilla juncea L. Journal of the Australian Institute of Agricultural Science 53(2): 83-95
2. Joe DiTomaso, UC Davis, pers. obs.
3. Bob Case, California Native Plant Society, pers. obs..


Question 1.3 Impact on higher trophic levels? U
Identify type of impact or alteration:

no information


Sources of information:

Question 1.4 Impact on genetic integrity? D Other Published Material

None No native Chondilla in California.


Sources of information:

Hickman, J. C. (ed.) 1993. The Jepson Manual, Higher Plants of California. University of California Press. Berkeley, CA enter text here


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

Inhabits cultivated areas and open, waste areas with disturbed soil (1). The optimal level of disturbance is equivalent to wheat/fallow cultivation and greater or lesser disturbance produces lower population levels (2). Mostly a roadside invader, but can expand away from roads into roadside corridors with grass or trees (3).


Sources of information:

1. Panetta, F. D. and J. Dodd. 1987. The biology of Australian weeds. 16. Chondrilla juncea L. Journal of the Australian Institute of Agricultural Science 53(2): 83-95
2. Wapshere, A. J., S. Hasan, and L. Caresche. 1974. The ecology of Chondrilla juncea in the western Mediterranean. Journal of Applied Ecology 11(2): 783-799
3. Personal communication, Carri Pirosko, CA Dept. of Food and Agriculture .


Question 2.2 Local rate of spread with no management? B Observational
Describe rate of spread:

Slowly expanding in at least some areas.


Sources of information:

1. Personal communication, Wendy West, UC Cooperative Extension, El Dorado county.
2. Personal communication, Carri Pirosko, CA Dept. of Food and Agriculture


Question 2.3 Recent trend in total area infested within state? B Observational
Describe trend:

Probably expanding within state, slowly to moderately (1, 2).


Sources of information:

1. Personal communication, Wendy West, UC Cooperative Extension, El Dorado county.
2. Personal communication, Carri Pirosko, CA Dept. of Food and Agriculture


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

Herbaceous. Long-lived perennial in Australia but behaves as a biennial in its native range. An individual plant can produce >20,000 seeds, but first year plants produce 250-350 seeds (1). In Australia, plants produced up to 27600 seeds with 80-90% viability (2). Produces seeds over a long period each year and plants less than one year old can reproduce (3). Adventitious buds at the top of the tap root and along the major laterals give rsie to daughter rosettes in undisturbed plants. Root break easily with soil disturbance. Adventitious shoots can arise from root fragments throughout the year (3). According to one study, most seeds lose viability within 1 year (4). However, data from a North American study suggested that non-germinating seeds are viable and may be able to persist past one year (5). However, seed viability decreases to 2% by the third year (6). All reproduction is vegetative or from asexual seed production (6).


Sources of information:

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

Contaminant of hay. Could be spread by attaching to livestock (see question 2.6), but probably only contributes to a minor degree to long distance transport (1). Can disperse along highways (2).


Sources of information:

1. Panetta and Dodd 1987
2. Bob Case, California Native Plant Society, pers. obs.


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

Wind, attachment to fur.


Sources of information:

1. Panetta and Dodd 1987


Question 2.7 Other regions invaded? B Other Published Material
Identify other regions:

Listed as a noxious weed in Australia (1). As of 2000, covered 2.5 million ha of rangeland in the Pacific northwest and California. Invades sagebrush steppe in Idaho (2). Does not seem to be in sagebrush areas of California yet.


Sources of information:

1. Panetta and Dodd 1987
1. Liao et al. 2000.


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

Occurs in disturbed soils of roadsides, croplands, semi-arid pastures, rangelands, and residential properties. Grows best on well-drained sandy or gravelly soils in climates with cool winters and hot, relatively dry summers. Tolerates a wide range of environmental conditions, including rain from 250mm (10in) to >1200mm (50in)/year. Present in North Coast, Cascade Range, northern Sierra Nevada, Central Valley, San Francisco Bay Area, South Coast Range, and South Coast, to 600m (1). Very widespread in California (2). Only occasionally in wildland areas, mostly grasslands. Most often found along roadsides.


Sources of information:

1. DiTomaso and Healy in press
2. Personal communication, Carri Pirosko, CA Dept. of Food and Agriculture .


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

Not very common in California. Biocontrol agents have been shown to reduce populations in other western states.


Sources of information:

Observational, DiTomaso


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 Yes
Seeds remain viable in soil for three or more years No
Viable seed produced with both self-pollination and cross-pollination No
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 Yes
Total points: 6
Total unknowns: 0
Total score: A?

Related traits:

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
estuaries
Dunescoastal
desert
interior
Scrub and Chaparralcoastal bluff scrub
coastal scrubD, < 5%
Sonoran desert scrub
Mojavean desert scrub (incl. Joshua tree woodland)
Great Basin scrubD, < 5%
chenopod scrub
montane dwarf scrub
Upper Sonoran subshrub scrub
chaparral
Grasslands, Vernal Pools, Meadows, and other Herb Communitiescoastal prairie
valley and foothill grasslandD, < 5%
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 woodlandD, < 5%
piñon and juniper woodland
Sonoran thorn woodland
Forestbroadleaved upland forest
North Coast coniferous forest
closed cone coniferous forest
lower montane coniferous forestD, < 5%
upper montane coniferous forest
subalpine coniferous forest
Alpine Habitatsalpine boulder and rock field
alpine dwarf scrub
Amplitude (breadth): B
Distribution (highest score): D

Infested Jepson Regions

Click here for a map of Jepson regions

  • Cascade Range
  • Central West
  • Mojave Desert
  • Great Valley
  • Modoc Plateau
  • Northwest
  • Sierra Nevada
  • Southwest