Plant Assessment Form

Senecio jacobaea

Common Names: tansy ragwort; stinking willie; stavewort; kettle-dock; felonweed; Fairies' horse; tansy butterweed; staggerwort

Evaluated on: 8/10/04

List committee review date: 27/08/2004

Re-evaluation date:

Evaluator(s)

Brianna Richardson, Project Manager
California Invasive Plant Council
1442-A Walnut Street #462, Berkeley, CA 94709
510.843.3902
brichardson@cal-ipc.org

List commitee members

Joe DiTomaso
Alison Stanton
Peter Warner
John Randall
Jake Sigg
Cynthia Roye

General Comments

No general comments for this species

Table 2. Criteria, Section, and Overall Scores

Overall Score? Limited
Alert Status? No Alert
Documentation? 3 out of 5
Score Documentation
1.1 ?Impact on abiotic ecosystem processes C Other Published Material
Impact?
Four-part score CCBC Total Score
C
1.2 ?Impact on plant community C. Minor Other Published Material
1.3 ?Impact on higher trophic levels B. Moderate Other Published Material
1.4 ?Impact on genetic integrity C. Minor/Low Other Published Material
2.1 ?Role of anthropogenic and natural disturbance in establishment C. Minor Other Published Material
Invasiveness?
Total Points
12 Total Score B
2.2 ?Local rate of spread with no management A. Increases rapidly Other Published Material
2.3 ?Recent trend in total area infested within state D. Declining Other Published Material
2.4 ?Innate reproductive potential
(see Worksheet A)
A. High Other Published Material
2.5 ?Potential for human-caused dispersal B. Moderate Other Published Material
2.6 ? Potential for natural long-distance dispersal B. Occasional Other Published Material
2.7 ?Other regions invaded C. Already invaded 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)
C. Low

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:

Dense infestations can increase soil erosion. May increase productivity among some pasture species. This in turn, may reduce microbial biomass in the soil. Only one source identified the ability of ragwort to increase soil erosion. Microbial biomass decreases appear to be a concern primarily in pastures.


Sources of information:

Coombs, EM, PB McEvoy, CE Turner. 1999. Tansy ragwort. In: Biology and Management of Noxious Rangeland Weeds. Sheley, RL, JK Petroff (eds.)
Wardle, DA. 1987. The ecology of ragwort (Senecio jacobaea L.)--A review. New Zealand Journal of Ecology. V.10: 67-76.


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

Can crowd out desireable forage species. Can form dense infestations when disturbance occurs. Pristine plant communities are generally resistant to ragwort infestation. Micro-disturbances in the soil created by rodent burrows and deer tracks can provide sufficient habitat for ragwort to invade and maintain its presence in less disturbed plant communities. Once established, ragwort can compete with grasses and clover. The dead rosette opens a space for germination of the seeds. Ragwort can dominate in highly disturbed plant communities. In OR, populations of the rare Sidalcea hirtipes increased >40% after ragwort biocontrols were released. Ragwort has been shown to inhibit seed germination and seedling emergence and growth of Lolium perenne and several legumes through allelopathy. Legumes were more affected by this. However, ragwort may increase productivity among some pasture species. Ragwort acts as a ruderal, colonizing after disturbance and relatively transient during periods of stability. More competitive at the rosette stage. Most literature focuses on the agricultural impacts of ragwort. Little evidence is available to support the idea that it can significantly threaten native plants. Though, it has impacted them in OR, no data was available for CA.


Sources of information:

Mitich, LW. 1995. Intriguing world of weeds: Tansy ragwort. Weed Technology. V.9: 402-404.here
Coombs, EM, PB McEvoy, CE Turner. 1999. Tansy ragwort. In: Biology and Management of Noxious Rangeland Weeds. Sheley, RL, JK Petroff (eds.)
Bain, JF. 1991. The biology of Canadian weeds. 96. Senecio jacobaea L. Canadian Journal of Plant Science. V.71: 127-140.
Ahmed, M., DA Wardle. 1994. Allelopathic potential of veggetative and flowering ragwort (Senecio jacobaea L.) plants against associated pasture species. Plant and Soil. V.164: 61-68.
Wardle, DA. 1987. The ecology of ragwort (Senecio jacobaea L.)--A review. New Zealand Journal of Ecology. V.10: 67-76.


Question 1.3 Impact on higher trophic levels? B Other Published Material
Identify type of impact or alteration:

Contains pyrrolizidine alkaloids and is toxic to livestock and deer when grazed in a single large quantity or in small quantities over time. Has cause serious livestock losses in PNW. May be accidentally ingested by animals in the seedling stage. Young livestock is 2-3 times more susceptible to poisoning than older animals. Adult animals must eat 5-7% of their body weight to die. Many animals prefer other forage over tansy ragwort. Numerous insects pollinate it. In OR, ragwort provides an additional nectar source for the threatened Speyeria zerene hippolyta butterfly. May be a poisoning threat to deer.


Sources of information:

DiTomaso, J., E. Healy. Weeds of California and Other Western States. Not yet published.
Coombs, E., C. Mallory-Smith, LC Burrill, RH Callahan, R. Parker, H. Radtke. 1997. Weeds: Tansy ragwort (Senecio jacobaea L.). Pacific Northwest Weed Notes. Oregon State University Extension Service publication.
Mitich, LW. 1995. Intriguing world of weeds: Tansy ragwort. Weed Technology. V.9: 402-404.


Question 1.4 Impact on genetic integrity? C Other Published Material

No hybrids have been reported from North America. Many native Senecios exist. Does coexist w/native, potential exists, but has not been documented. Possible a pollen swamping situation exists on the Medocino coast with the native, rare S. bolanderi.


Sources of information:

Bain, JF. 1991. The biology of Canadian weeds. 96. Senecio jacobaea L. Canadian Journal of Plant Science. V.71: 127-140.
PW, JD


Section 2: Invasiveness
Question 2.1 Role of anthropogenic and natural disturbance
in establishment?
A Other Published Material
Describe role of disturbance:

Open areas result in better seedling establishment. One of the first plants to colonize cut-over forests. Rodent mounding and scratching can create ideal establishment conditions. Most references indicate that disturbance is required for ragwort establishment. Disturbance is required for germination of dormant, buried seeds. All literature notes that establishment requires disturbance.


Sources of information:

DiTomaso, J., E. Healy. Weeds of California and Other Western States. Not yet published.
Coombs, E., C. Mallory-Smith, LC Burrill, RH Callahan, R. Parker, H. Radtke. 1997. Weeds: Tansy ragwort (Senecio jacobaea L.). Pacific Northwest Weed Notes. Oregon State University Extension Service publication.
Coombs, EM, PB McEvoy, CE Turner. 1999. Tansy ragwort. In: Biology and Management of Noxious Rangeland Weeds. Sheley, RL, JK Petroff (eds.)
Wardle, DA. 1987. The ecology of ragwort (Senecio jacobaea L.)--A review. New Zealand Journal of Ecology. V.10: 67-76.


Question 2.2 Local rate of spread with no management? A Other Published Material
Describe rate of spread:

In MT, one infestation has "expanded exponentially" since it was first discovered in 1993 (in 1997 it covered 1500 net acres over 150 sq.miles.) Ragwort can dominate an area in less than 10 years if disturbance occurs (ex. overgrazing, logging). Can double in less than 10 years if appropriate habitat is available.


Sources of information:

Mott, Gary. 1997. Tansy ragwort (Senecio jacobaea) briefing paper. Western Area Weed Council. (This is a memo or email)
Coombs, EM, PB McEvoy, CE Turner. 1999. Tansy ragwort. In: Biology and Management of Noxious Rangeland Weeds. Sheley, RL, JK Petroff (eds.)


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

Populations have been dramatically reduced in CA and OR since the introduction of two biocontrols (Tyria jacobaeae, Longitarsus jacobaeae). Biocontrols have greatly reduced populations of ragwort.


Sources of information:

DiTomaso, J., E. Healy. Weeds of California and Other Western States. Not yet published.


Question 2.4 Innate reproductive potential? A Other Published Material
Describe key reproductive characteristics:

Annual, biennial, or perennial. Behaves as a short-lived perennial when mowed, grazed or injured. Develops many spreading lateral roots, which can send up new shoots in response to injury; and which can produce new shoots if fragmented. Flowers July-September. Each shoot produces 20-60 flower heads with numerous disk and ray flowers on each head. Seeds typically remain viable in the soil for 6 years, may remain viable for up to 20 yrs. A single plant can produce 5,000-200,000 seeds over a 4-6 week period. 9 points.


Sources of information:

DiTomaso, J., E. Healy. Weeds of California and Other Western States. Not yet published.
Coombs, E., C. Mallory-Smith, LC Burrill, RH Callahan, R. Parker, H. Radtke. 1997. Weeds: Tansy ragwort (Senecio jacobaea L.). Pacific Northwest Weed Notes. Oregon State University Extension Service publication.
Mitich, LW. 1995. Intriguing world of weeds: Tansy ragwort. Weed Technology. V.9: 402-404.
Wardle, DA. 1987. The ecology of ragwort (Senecio jacobaea L.)--A review. New Zealand Journal of Ecology. V.10: 67-76.
PW, JD, JR


Question 2.5 Potential for human-caused dispersal? B Other Published Material
Identify dispersal mechanisms:

Spread by agricultural equipment, human activity, on the tires of vehicles, and on the shoes and clothes of people. Can be spread in contaminated hay or straw. Seeds may be spread in the manure of livestock. Can be spread by fire-fighting activity. Human dispersal is unintentional but does occur.


Sources of information:

DiTomaso, J., E. Healy. Weeds of California and Other Western States. Not yet published.
Coombs, E., C. Mallory-Smith, LC Burrill, RH Callahan, R. Parker, H. Radtke. 1997. Weeds: Tansy ragwort (Senecio jacobaea L.). Pacific Northwest Weed Notes. Oregon State University Extension Service publication.
Mott, Gary. 1997. Tansy ragwort (Senecio jacobaea) briefing paper. Western Area Weed Council. (This is a memo or email)


Question 2.6 Potential for natural long-distance dispersal? B Other Published Material
Identify dispersal mechanisms:

Seeds can be dispersed a short distance (a few meters) by wind. While not verified, very strong winds may be able to blow seeds many kilometers, but only if they are pulled into the atmosphere. Water dipsersal is likely. Also dispersed by clinging to the fur, feathers, and feet of animals. Seeds may survive ingestion by birds, but some experiments have found this unlikely. Occassionally dispersed long distances by animals and water.


Sources of information:

DiTomaso, J., E. Healy. Weeds of California and Other Western States. Not yet published.
Wardle, DA. 1987. The ecology of ragwort (Senecio jacobaea L.)--A review. New Zealand Journal of Ecology. V.10: 67-76.


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

State-listed noxious weed in AZ, CO, ID, OR, WA. Distribution includes ID, MT, OR, WA to British Columbia, IL, MI, some northeastern states. Naturalized in India, Africa, Canada, Argentina, Australia, and New Zealand. Occurs along beaches in OR. Same ecotypes as in CA.


Sources of information:

DiTomaso, J., E. Healy. Weeds of California and Other Western States. Not yet published.
Mitich, LW. 1995. Intriguing world of weeds: Tansy ragwort. Weed Technology. V.9: 402-404.
Coombs, EM, PB McEvoy, CE Turner. 1999. Tansy ragwort. In: Biology and Management of Noxious Rangeland Weeds. Sheley, RL, JK Petroff (eds.)


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

First reported in OR in 1922. Disturbed sites, waste places, roadsides, pastures, fields, rangeland, near riparian areas, forested areas. Inhabits grassland, woodland, and dunes in its native range. Often found in grasslands, cut-over forests, nonirrigated patures, and woodland pastures in PNW. Inhabits at least 3 major ecotypes and 6 minor in CA.


Sources of information:

DiTomaso, J., E. Healy. Weeds of California and Other Western States. Not yet published.
Coombs, E., C. Mallory-Smith, LC Burrill, RH Callahan, R. Parker, H. Radtke. 1997. Weeds: Tansy ragwort (Senecio jacobaea L.). Pacific Northwest Weed Notes. Oregon State University Extension Service publication.
Bain, JF. 1991. The biology of Canadian weeds. 96. Senecio jacobaea L. Canadian Journal of Plant Science. V.71: 127-140.


Question 3.2 Distribution/Peak frequency? C
Describe distribution:

North Coast, western Klamath Ranges, soutwestern Cascade Range, northern Sierra Nevada, northern Sacramento Valley, San Francisco Bay region. Requires areas of sufficient rainfall. Infests 3 million acres in the PNW including northern CA. Requires a climate similar to central Europe, cooler and wetter than much of California. Dry summer months greatly inhibit seedling establishment. present in at least 6-20% of north coast coniferous forest


Sources of information:

DiTomaso, J., E. Healy. Weeds of California and Other Western States. Not yet published.
Mitich, LW. 1995. Intriguing world of weeds: Tansy ragwort. Weed Technology. V.9: 402-404.
Coombs, EM, PB McEvoy, CE Turner. 1999. Tansy ragwort. In: Biology and Management of Noxious Rangeland Weeds. Sheley, RL, JK Petroff (eds.)
Wardle, DA. 1987. The ecology of ragwort (Senecio jacobaea L.)--A review. New Zealand Journal of Ecology. V.10: 67-76.
Observational, List Committee, 8/2004.


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 Yes
Viable seed produced with both self-pollination and cross-pollination Yes
Has quickly spreading vegetative structures (rhizomes, roots, etc.) that may root at nodes Yes
Fragments easily and fragments can become established elsewhere No
Resprouts readily when cut, grazed, or burned Yes
Total points: 9
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
DunescoastalD, < 5%
desert
interior
Scrub and Chaparralcoastal bluff scrub
coastal scrub
Sonoran desert scrub
Mojavean desert scrub (incl. Joshua tree woodland)
Great Basin scrub
chenopod scrub
montane dwarf scrub
Upper Sonoran subshrub scrub
chaparral
Grasslands, Vernal Pools, Meadows, and other Herb Communitiescoastal prairieD, < 5%
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 forestD, < 5%
riparian woodlandD, < 5%
riparian scrub (incl.desert washes)
Woodlandcismontane woodland
piñon and juniper woodland
Sonoran thorn woodland
Forestbroadleaved upland forest
North Coast coniferous forestC, 5% - 20%
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): A
Distribution (highest score): C

Infested Jepson Regions

Click here for a map of Jepson regions

  • CA Floristic Province
  • Cascade Range
  • Central West
  • Mojave Desert
  • Great Valley
  • Northwest
  • Sierra Nevada
  • Southwest