Conyza sumatrensis is an annual herb probably native to South America, but widely naturalised in tropical and subtropical regions, and regarded as an invasive weed in many places. In the British Isles it is known as Guernsey fleabane. Other common names include fleabane, tall fleabane, broad-leaved fleabane, white horseweed, and Sumatran fleabane.
When fully grown (in summer or autumn), Conyza sumatrensis reaches one to two metres in height. Flowers are white rather than purple-pink. Its leaves are like dandelion leaves, but longer, thinner and more like primrose leaves in colour and texture. Its seeding heads are like dandelions, but straw coloured and smaller. In certain countries the plant has started to exhibit resistance to herbicides.
It probably originates from South America, but is now naturalised in North America, Europe, Africa, Asia, and Australasia. It poses a significant threat to wildlife conservation areas and other reserves. In Britain, of the alien British Conyza species, this is the second most abundant (after C. canadensis) and is typically found in London and the South East of England. It was first recorded in London by Brian Wurzell in 1984, and noted in France at Saint-Sozy (Dordogne) in 2006.
Its invasive nature and competitive ability could suppress the native flora in the more open habitats it favours.
- Flora of China, 苏门白酒草 su men bai jiu cao Erigeron sumatrensis Retzius
- Pruski, J.F. & G. Sancho. 2006. Conyza sumatrensis var. leiotheca (Compositae: Astereae), a new combination for a common neotropical weed. Novon 16(1): 96–101
- "BSBI List 2007". Botanical Society of Britain and Ireland. Archived from the original (xls) on 2015-01-25. Retrieved 2014-10-17.
- See pictures at International Environmental Weed Foundation
- Sumatran Fleabane, Weedscience.org
- Fleabane in Holland
- Flora of Zimbabwe: Conyza sumatrensis
- Sumatran Fleabane in Japan
- Pacific Island Ecosystems at Risk (PIER): Conyza sumatrensis
- Fleabane in London
- Mark Galliott (June 2006). "France – The Dordogne" (PDF). Tour Report. Naturetrek Wildlife Holidays. Archived from the original (PDF) on 2007-09-29. Retrieved 2011-10-18.
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