Who has not spent hours picking long, barbed seeds of Bidens pilosa out of socks and trousers? This is one plant we are sure you will know, even if the various names are unfamiliar. We recognise this plant as a weed, common in gardens, along paths and roadways and in agricultural crops. Its natural distribution is in the tropical regions of South, Central and North America, with Mexico considered to be the centre of diversification for the species. It is now widespread throughout the world. Bidens pilosa is a daisy, one of about 230 species of Bidens in the plant family family Asteraceae. It grows rapidly into a soft, erect annual herb with yellow flowers surrounded by white petals. Actually, each Bidens pilosa - flower is a cluster of numerous tiny, closely- natural distribution packed yellow flowers (florets). A few of the outermost florets have just one large white petal, giving the whole cluster of flowers the appearance of just one flower. Bidens pilosa – present day world-wide distribution CABI: https://www.cabi.org/isc/datasheet/9148 The seeds are the problem. Each flower head develops into a ball of barbed seeds, each barbed spine ornate with yet more tiny barbs, perfect for hooking into fur or clothing, ensuring super-efficient dispersal. Bidens pilosa is of great interest for another reason. It was collected by botanists Joseph Banks and Daniel Solander who sailed with Cook in the Endeavour, in Botany Bay in 1770, one of 132 plant species collected there. It is easy to assume that plants present in Australia prior to the arrival of the Endeavour are native plants, but is this correct? Is B. pilosa an Australian native plant or is it an exotic plant that has been introduced into Australia. And if its origins really are in Mexico, how did it get to Botany Bay? During Cook’s second voyage to the Pacific (1772 to 1775), botanists J R Forster and G Forster collected yet more weeds from Pacific islands; most came originally from the Americas, brought to the various Pacific Islands by Spanish ships during the preceding 200 years. Before Cook landed in Botany Bay in 1770, no fewer than 54 European ships had been recorded in Australian waters, and as botanist A R Bean (2007) commented: This was only a selection of visits made, but serves to highlight that there was a lot of traffic along the Australian coastline Routes of some European maritime explorers, prior to the before the arrival of Captain Cook. arrival of Captain Cook in Botany Bay. Bean 2007. Doubtless, molecular studies will unravel the true origins of the Bidens pilosa specimen collected by Banks and Solander in Botany Bay. Alison Downing, Brian Atwell Kevin Downing Department of Biological Sciences Bean A R. 2007. A new system for determining which plant species are indigenous in Australia. Australian Systematic Botany 20: 1–43 Benson D, Eldershaw G, 2007. Backdrop to encounter: the 1770 landscape of Botany Bay, the plants collected by Banks and Solander and rehabilitation of natural vegetation at Kurnell. Cunninghamia 10(1): 113 – 137. Invasive Species Compendium CABI: https://www.cabi.org/isc/datasheet/9148 Queensland Government, Weeds of Australia: https://keyserver.lucidcentral.org/weeds/data/media/Html/bidens_pilosa.htm Plantnet: http://plantnet.rbgsyd.nsw.gov.au/cgi-bin/NSWfl.pl?page=nswfl&lvl=gn&name=Bidens .