Photo: John Beall

Senecio angulatus Risk Assessment

Synonyms: Senecio macropodus, Senecio canalipes, Senecio tredecimsquamosus

Common names: Creeping groundsel, climbing groundsel, Cape ivy

Senecio angulatus -- California

Primary tabs

Created by: Ron Vanderhoff
Created on: Thursday, Sep 19th, 2024
Evaluation Summary
Senecio angulatus is native to South Africa. It is a prolific, climbing, perennial, herbaceous plant that has been introduced as an ornamental mostly in temperate countries. It is a fast-growing plant with the potential to become an aggressive weed. Once established, it may form thickets and dense patches of more than 20 m that can cover, shade and smother native flora. S. angulatus produces large numbers of (possibly non-viable) seeds; and stem fragments can also easily root, often from discarded plant waste. It has escaped cultivation and currently, it is regarded as an invasive plant or weed in parts of Spain, Italy, Australia and New Zealand. There, it often forms dense infestations in open and disturbed areas, particularly along coastal habitats. In California it thus far has a patchy wildland distribution, primarily coastally from Santa Barbara to the Mexico border. Senecio angulatus is a significant wildlands invader in other Mediterranean climate areas. It is described as "One of the most invasive species in the western Mediterranean" (Brundu et al., 1999) and "Spreading ("major invader") in Mediterranean France" (Brunel and Tison, 2005). Senecio angulatus is very similar in appearance, habit, and habitat to invasive Delairea odorata, especially when not in flower. There may be a portion of California observations misidentified for this reason.
General Evaluation Information
Date of Evaluation: 
December 28, 2024
Evaluation Time (hrs): 
10 Hours
Evaluation Status: 
Completed
Plant Information
Plant: 
Senecio angulatus
Plant Material: 
If the plant is a cultivar, and if the cultivar's behavior differs from its parent's (behavior), explain how: 
The plant is not a cultivar.
Regional Information
Region Name: 
California
Climate Matching Map
These maps were built using a toolkit created in collaboration between GreenInfo Network, PlantRight, Cal-IPC, and Agricultural Sustainability Institute at UC Davis.
PRE Climate Map (external link)
Climate Matching Maps PDF: 
AttachmentSize
PDF icon ClimateMatch-Senecio_angulatus-California-20250207.pdf1.16 MB
Invasive History and Climate Matching
1. Has the species (or cultivar or variety, if applicable; applies to subsequent "species" questions) become naturalized where it is not native?
Yes or No: 
Yes
Points: 
1
Confidence Level: 
Very High
Answer / Justification: 
Yes. Senecio angulatus is native to South Africa and widely naturalized in many places such as Spain, France, Australia, New Zealand, Italy, Portugal, Croatia, Chile, Albania, and Tunisia, as well as California and Baja California. (iNat Observations, Calflora, GBIF, GISD, CABI) Altough not yet declared invasive, the plant is targeted by the Oregon Department of Agriculture for early detection and fast response if it were to escape from cultivation. (USDA APHIS) On the Costa Brava in Spain, it was one of the five most recorded species, where it was found in large assemblage, usually close to human residence, invading and colonizing the clifftops, roadsides and the proximate scrubland, including the undergrowth, replacing native flora species such as Pistacia lentiscus. It was introduced to Catalonia in the 1970s as a groundcover plant in home gardens, before escaping. It is one of the most common alien species present on the Catalan coast. (MedCliffs Life)
Reference(s): 
2. Is the species (or cultivar or variety) noted as being naturalized in the US or world in a similar climate?
Yes or No: 
Yes
Points: 
2
Confidence Level: 
Very High
Answer / Justification: 
Yes. Senecio angulatus is widely naturalized in many places with temperate or Mediterannean climates, and in California climate matching areas such as Spain, Australia, New Zealand, Italy, Portugal, Croatia, and Chile, as well as Baja California. (iNat Observations, GBIF, GISD, CABI) The plant is targeted by the Oregon Department of Agriculture for early detection and fast response if it were to escape from cultivation. (USDA APHIS) On the Costa Brava in Spain, a climate matching area, it was one of the five most recorded species, where it was found in large assemblage and is one of the most common alien species present on the Catalan coast, a climate matching area. (MedCliffs Life)
Reference(s): 
3. Is the species (or cultivar or variety) noted as being invasive in the U.S. or world?
Yes or No: 
Yes
Points: 
2
Confidence Level: 
Very High
Answer / Justification: 
Yes. Senecio angulatus is reported as invasive in Spain, Australia, New Zealand and Italy (CABI, GISD). Although not yet declared as invasive, the plant was evaluated as "High risk" by the Oregon Department of Agriculture for early detection and fast response if it were to escape from cultivation (USDA APHIS).
Reference(s): 
4. Is the species (or cultivar or variety) noted as being invasive in the US or world in a similar climate?
Yes or No: 
Yes
Points: 
3
Confidence Level: 
Very High
Answer / Justification: 
Yes. Senecio angulatus is reported as invasive in Spain, Australia, New Zealand and Italy, all in areas with a California climate match (CABI, GISD). Additionally, the plant was evaluated as "High risk" by the Oregon Department of Agriculture (also with a California Climate match) for early detection and fast response if it were to escape from cultivation (USDA APHIS).
Reference(s): 
5. Are other species of the same genus (or closely related genera) invasive in a similar climate?
Yes or No: 
Yes
Points: 
1
Confidence Level: 
Very High
Answer / Justification: 
Yes, many species in the large genus Senecio (and related genera) are declared invasive in California and California climate matching areas. Cal-IPC has declared Senecio elegans, Senecio glomeratus, Senecio jacobaea, and Senecio linearifolius as an invasive species in California (Cal-IPC). GISD reports Senecio inaequidens, squalidus and viscosus as addiional examples of invasive Senecios in climate matched areas of the world (GSID). The closely related Delairea odorata (formerly Senecio makanoides), and Jacobaea vulgaris are declared invasive species in California (Cal-IPC).
Reference(s): 
6. Is the species (or cultivar or variety) found predominately in a climate matching the region of concern?
Yes or No: 
Yes
Points: 
2
Confidence Level: 
High
Answer / Justification: 
Using the climate matching tool this species is almost perfectly divided beween occuring in a California climate matching area and not. 58 climate matching areas were counted and 57 without a climate match. However, because this tool is a binary yes/no score of occurrance in polygon areas and not a quanitative obsevation count it is highly likely that a more fine scale analysis would place a good majority of the individual observation points within the areas of climate match. I feel confident in a YES answer to this question, yet purely from the close area count I am scoring a Medium confidence (Cal-IPC Climate Match Tool).
Reference(s): 
Impact on Native Plants and Animals
7. Does this plant displace native plants and dominate (overtop or smother) the plant community in areas where it has established?
Yes or No: 
Yes
Points: 
1
Confidence Level: 
Very High
Answer / Justification: 
Several sources document the species growth habit as rather clearly displacing native plants and dominating plant communities. Because it forms dense vine tangles and mats (Bergin, 2006; USDA, APHIS, 2013), Senecio angulatus changes community structure, alters species composition (Newton, 1996; Weber, 2011; USDA, APHIS, 2013), reduces regeneration of native species (Williams, 2007), and is likely to threaten rare species.
Reference(s): 
8. Is the plant noted as promoting fire and/or changing fire regimes?
Yes or No: 
No
Points: 
0
Confidence Level: 
Medium
Answer / Justification: 
I find no published information about any of the plants impacts on fire. Given that it is a semi-succulent herbaceuous perennial, it is doubtful it would host fire impacts.
Reference(s): 
9. Is the plant a health risk to humans or animals/fish? Has the species been noted as impacting grazing systems?
Yes or No: 
Yes
Points: 
1
Confidence Level: 
Very High
Answer / Justification: 
Numerous publications report toxicity as common in plants in the genus Senecio. Senecio species contain hepatotoxic pyrrolizidine alkaloids (PAs), which if grazed can induce irreversible liver damage. Senecio species in general are known to be toxic to livestock and humans (Burrows and Tyrl, 2001). Senecio angulatus is toxic to both humans and pets according to The American Society for the Prevention of Cruelty to Animals. If ingested, it can cause vomiting, diarrhea and abdominal pains (Homeplantsguide, altough this is a secondary source with no reference citation and marginally validated). In South Africa, Senecio angustifolius contaminates Rooibos tea (Aspalathus linearis (Burm.f.) R.Dahlgren). Unfortunately, S. angustifolius has a similar growth habit and flower color as A. linearis, making it difficult to eliminate from Rooibos plantations. As the invading species grows among the Rooibos plants, it secretes pyrrolizidine alkaloids into the rhizosphere, where they are enter the root system of A. linearis and accumulate in the tea leaves. (VanWyk, e al) A 1962 paper documenting toxic alkaloids within the plant tissues further supports the conclusion of its toxicity. (Porter, 1962)
Reference(s): 
10. Does the plant produce impenetrable thickets, blocking or slowing movement of animals, livestock, or humans?
Yes or No: 
Yes
Points: 
1
Confidence Level: 
High
Answer / Justification: 
There is considerable documentation in the literature of the growth habit of the species. It readily forms dense infestations in open/disturbed areas, particularly coastal environments (Champion, 2005; Williams, 2007). S. angulatus is a prolific vine that has the ability to form thickets of more than 20 mteres that can cover and smother native flora (GISD). Bergin documents the species "forms dense vine tangles and mats" (Bergin, 2006; USDA, APHIS, 2013), suggesting an interference with animal movement. Not specifically discussing impacts to animal movement, but perhaps inferring it are Newton comments: "Senecio angulatus changes community structure, alters species composition" (Newton, 1996; Weber, 2003; USDA, APHIS, 2013). And Williams states "reduces regeneration of native species and is likely to threaten rare species" (Williams, 2007). Numerous in-situ photo images show dense mats and vegetation tangles, strongly inferring "blocking or slowing movement of animals, livestock or humans" (iNat, Calflora). Florabase is even clearer, stating "Completely smothers ground-flora vegetation and smaller shrubs". (Florabase)
Reference(s): 
Reproductive Strategies
11. Does this species (or cultivar or variety) reproduce and spread vegetatively?
Yes or No: 
Yes
Points: 
1
Confidence Level: 
Very High
Answer / Justification: 
Yes. The species is clearly documented as reproducing and spreading vegetatively. In fact, its seed may not be viable. This species spreads through seeds(?) and stem fragments that can easily root (FloraBase, 2013; Hussey et al., 2007; Williams, 2007). Yard waste is believed to be a significant pathway for its spread, because it can establish from plant fragments (Hussey et al., 2007; Williams, 2007). This species reproduces by seed(?) and also via stem segments. Its seed are dispersed by wind and animals, while its seeds and stem segments can also be spread in dumped garden waste (CABI).
Reference(s): 
12. If naturally detached fragments from this plant are capable of producing new plants, is this a common method of reproduction for the plant?
Yes or No: 
Yes
Points: 
1
Confidence Level: 
High
Answer / Justification: 
Yes. The species is clearly documented as reproducing and spreading vegetatively. In fact, its seed may not be viable. This species spreads through seeds(?) and stem fragments that can easily root (FloraBase, 2013; Hussey et al., 2007; Williams, 2007). Yard waste is believed to be a significant pathway for its spread, because it can establish from plant fragments (Hussey et al., 2007; Williams, 2007). This species reproduces by seed(?) and also via stem segments. Its seed are dispersed by wind and animals, while its seeds and stem segments can also be spread in dumped garden waste. (CABI)
Reference(s): 
13. Does the species (or cultivar or variety) commonly produce viable seed?
Yes or No: 
Yes
Points: 
1
Confidence Level: 
Medium
Answer / Justification: 
Although this plant is well documented to produce copious quantities of seed, there is also modest documentation of the seed being either sterile or not viable outside of its native area of distribution. I can find no specific evidence that this species has produced viable seen anywhere in CA. The answer to this question about "viable" seed would still be "Yes", altough the apparent differences in seed viability regionally should be noted. CABI reports "A study in Wellington (New Zealand) found that S. angulatus is self-incompatible and no seeds were produced in the study site. However, artificial hand-pollination experiments suggest that a lack of pollinators is not the reason for the limited seed production. (CABI) "A vegetative experiment showed that cuttings of various ages and lengths had the ability to establish indicating that the predominant mode of dispersal of S. angulatus in the Wellington region is vegetative reproduction" (Scott, 2001). The same source continues "the predominant mode of dispersal of S. angulatus and D. odorata in the Wellington region is considered to be vegetative reproduction"(Scott, 2001). It would be reasonable speculation for non-viable seed in area away from its native range to be the result of self incompatability. This self incompatability could in-turn be due to a lack of genetic diversity in an alien population. However, over time, and with additional propagule recruitment, this non-viable seed trait could disappear. I am giving a "Yes" answer here, but only a medium confidence given some lack of published reseach and uncertainties about seed viability in different geographic areas.
Reference(s): 
14. Does this plant produce copious viable seeds each year (> 1000)?
Yes or No: 
No
Points: 
0
Confidence Level: 
High
Answer / Justification: 
Altough this plant is well documented to produce copious quantities of seed, there is also modest documentation of the seed being either sterile or not viable. In this case, the answer to this question about "viable" seed would be "No". Phillipa Scott, 2001 says "S. angulatus produces large numbers of seeds", but does not provide a count. CABI states "the predominant mode of dispersal of S. angulatus and D. odorata in the Wellington region is considered to be vegetative reproduction". (CABI) Finally Scott, 2001 continues saying "the presence of a sporophytic self-incompatibility mechanism. This supports the hypothesis that populations of S. angulatus and S. mikanioides [Delairea odorata] are both comprised of a single genotype, or at least are fixed for a single S allele so that seed is unable to be produced." (Scott, 2001) I am giving a "No" answer here, and a high confidence given the unlikely probability of >1,000 viable seeds.
Reference(s): 
15. Is there significant germination (>25%) of seeds the next growing season, with no requirement of an infrequent environmental condition for seeds to germinate (i.e. fire) or long dormancy period?
Yes or No: 
No
Points: 
0
Confidence Level: 
High
Answer / Justification: 
Altough this plant is well documented to produce copious quantities of seed, there is also modest documentation of the seed being either sterile or not viable. In this case, the answer to this germination question would be "No". Phillipa Scott, 2001 says "S. angulatus produces large numbers of seeds", but does not provide a count. CABI further says "the predominant mode of dispersal of S. angulatus and D. odorata in the Wellington region is considered to be vegetative reproduction". (CABI) Finally Scott says "the presence of a sporophytic self-incompatibility mechanism. This supports the hypothesis that populations of S. angulatus and S. mikanioides [Delairea odorata] are both comprised of a single genotype, or at least are fixed for a single S allele so that seed is unable to be produced." (Scott, 2001) I am giving a "No" answer here, and a high confidence, because >25% germination seems quite unlikely given the literature.
Reference(s): 
16. Does this plant produce viable seed within the first three years (for an herbaceous species) to five years (for a woody species) after germination?
Yes or No: 
Yes
Points: 
1
Confidence Level: 
Medium
Answer / Justification: 
This plant is a perennial scrambler/vine, it can set seed within its first year (FloraBase, 2013; Williams, 2007). However, this seed is presumed to be either sterile or non-viable outside of its native range. The New Zealand Plant Conservation Network states "Seed is believed to be non-viable. Seeds are spread by wind" meaning that reproduction, in New Zealand (a non-native location) would be purely vegetative (New Zealand Plant Conservation Network). I am giving a "Yes" answer, due to published statements about seed germination in the plants native range. But I am only offering a medium confidence given some other documentation about non-viable seed in most/all alien locations.
Reference(s): 
17. Does this plant continuously produce seed for >3 months each year or does seed production occur more than once a year?
Yes or No: 
Yes
Points: 
1
Confidence Level: 
Very High
Answer / Justification: 
Calflora reports flowering from April to November (8 months) (Calflora). A review of California observations on iNaturalist shows flowering at every month of the year. (iNat) The New Zealand Plant Conservation Network reports flowering during March, April, May, June, July, and August (New Zealand Network). There is doubt about seed viability in the species, but this apparently is not a consideration of the question.
Reference(s): 
Dispersal
18. Are the plant’s propagules frequently dispersed long distance (>100 m) by mammals or birds or via domestic animals?
Yes or No: 
No
Points: 
0
Confidence Level: 
Medium
Answer / Justification: 
Seeds are documented as wind dispersed (FloraBase, 2013; Weber, 2003; Williams, 2007), and very likely animal dispersed (FloraBase, 2013). However, seeds are not the likely or preferred method of dispersal and propagation for the species. Dispersal and propagation is primarily (or exclusively) from vegetative means, which is uncommon via mammals or domestic animals, but occasional from birds.
Reference(s): 
19. Are the plant’s propagules frequently dispersed long distance (>100 m) by wind or water?
Yes or No: 
Yes
Points: 
1
Confidence Level: 
Medium
Answer / Justification: 
Seeds are wind dispersed (FloraBase, 2013; Weber, 2003; Williams and Hayes, 2007), and very likely animal dispersed (FloraBase, 2013). Where the plant does produce viable seed it is wind dispersed, although the distance of this dispersal is less certain: Produces "fluffy seeds" that are dispersed a long way from the parent plant (WMC, 2013). Dispersed by wind (FloraBase, 2013; Weber, 2003; Williams and Hayes, 2007). "Achenes terete, with hairs on ribs" (Flora of New Zealand, 2013). "Produces an achene (i.e., a fruit that tightly envelopes a seed) that is 2.2 × 0.5 mm with a pappus" (bristles or feather-like hairs) (Newton, 1996). As noted elsewere, seeds are not necessarily viable in CA, amd not the likely or preferred method of dispersal and propagation for the species in CA. I cannot locate any specific documentation about water dispersal of stem fragments. But because the plant grows commonly on stream banks and reproduces easily from stem fragments, dispersal from detached stem fragments would seem very likely along water courses. One source indicates it is dispersed by water (FloraBase, 2013), but it provides no specific data or references. Because seeds of this species don't appear to be specifically adapted for water dispersal, seed dispersal by water is inconclusive and unknown. I am answering YES because of the documentation of seed dispersal by wind and the high likelihood of propagation from vegetative segments transported in stream water.
Reference(s): 
20. Are the plant’s propagules frequently dispersed via contaminated seed (agriculture or wildflower packets), equipment, vehicles, boats or clothing/shoes?
Yes or No: 
Yes
Points: 
1
Confidence Level: 
Medium
Answer / Justification: 
The plant is easily and commonly dispersed via garden waste and therefore presumably agriculture as well (Williams 2007, Hussey 2007, Florabase). Given the propensity of the species to root readily from stem fragments, dispersal via agriculture, equipment, and vehicles is almost certain. However, without a specific reference I am scoring only Medium confidence.
Reference(s): 
Evaluation Notes

This taxon scored highly and would appear to be a strong candidate for invasiveness in California. Published documentation is fairly thorough and complete.

Seed viability in California remains somewhat uncertain.

Total PRE Score

  • < 13 : Low Potential Risk
  • 13 - 15 : Moderate Potential Risk
  • > 15 : High Potential Risk

PRE Score: 
21
Number of questions answered: 
20
Screener Confidence (%): 
83.0
PRE Content Access and Privacy
Organization: 
California Invasive Plant Council (Cal-IPC)
2023-2024 Western IPM Project
Evaluation visibility: 
Public - accessible to all site users

Review this Evaluation

10420
Note: You have already reviewed this evaluation. Thanks!