Taxonomy
Conyza canadensis | Canadian Fleabane
Distribution
Status
Conservation status
Not Assessed
Native status
Non-native
First reported in the wild
1935
Invasiveness
Invasive species - risk of Medium Impact
Irish status
Occasionally present, casual, vagrant, migratory
Introduction pathways - 1
Transport Contaminant
Introduction pathways subclass - 1
Seed contaminant
Invasive score
14
NAPRA Ireland risk assessed
No
Species Biology
Identification
Tall erect, green, annual, up to 1m in height, green leaves (Stace, 1997).
Ecology
Considered a weed in its native range, it has a negative impact on species abundance and diversity when grown with species from outside its native range (Shah et al., 2014). Native species richness is inversely correlated with invasibility of Conyza spp suggesting it will have greater impacts on communities already subject to disturbance (Prieur-Richard et al., 2000).
Habitat
Inland unvegetated or sparsely vegetated habitats; Regularly or recently cultivated agricultural, horticultural or domestic habitat; Constructed, industrial or other artificial habitats
Reproduction
Seed production is related to height of plant: a plant 40 cm tall produces about 2000 seeds, while a plant 1.5 m tall plant can produce as much as 230 000 seeds (Weaver, 2001).
Pathway and vector description
Repeatedly reintroduced as contaminants in various seed mixtures, generally found on waste ground (Reynolds, 2002).
Mechanism of impact
Competition, Disease transmission
Broad environment
Terrestrial
Habitat description
Typically found on waste ground, roadsides, pavement edges, dunes and walls (Reynolds, 2002; Stace, 1997).
Species group
Plant
Native region
North America
Distribution
World distribution(GBIF)
Irish distribution
Occasional - Infrequent casual, localised (Reynolds, 2002). Rosslare Harbour is the only site that has persistent records for this species.
Native distribution
Native to North America, found in all parts of Canada (C. candensis) except Newfoundland (Weaver, 2001).
Temporal change
Date of first record category
1931-1940
Fifty year date category
1901-1950
Records submitted to Data Centre in 2024
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How can you help
Report any sightings to the National Biodiversity Data Centre.
References
Publications
Reynolds, S.C.P. (2002) A catalogue of alien plants in Ireland. National Botanic Gardens. Glasnevin, Dublin. Stace, C. (1997). New Flora of the British Isles 2nd Edition. Cambridge University Press, Cambridge. Weaver, S. E. (2001). The biology of Canadian weeds. 115. Conyza canadensis. Canadian Journal of Plant Science, 81(4), 867-875. Shah, M. A., Callaway, R. M., Shah, T., Houseman, G. R., Pal, R. W., Xiao, S., Luo, W., Rosche, C., Reshi, Z.A., Khas, D.P. & Chen, S. (2014). Conyza canadensis suppresses plant diversity in its nonnative ranges but not at home: a transcontinental comparison. New Phytologist, 202(4), 1286-1296. Prieur-Richard, A. H., Lavorel, S., Grigulis, K., & Dos Santos, A. (2000). Plant community diversity and invasibility by exotics: invasion of Mediterranean old fields by Conyza bonariensis and Conyza canadensis. Ecology Letters, 3(5), 412-422.