Shepherd’s Needles, a species native to much of its range in the United States, has been added to the USWildflowers database (01/15/2012.) Scientific name is Bidens pilosa. Photo below was taken in Sarasota County, FL, on December 18, 2011. Go to the Shepherd’s Needles detail page for more photos and information.
Shepherd’s Needles, Spanish Needles, Romerillo, Common Beggar’s-tick, Hairy Beggarticks, Cobbler’s Pegs – Bidens pilosa
From your article, it seems you are saying that Biden Pilosa and Alba are the same. How do you account for Pilosa having a hairy stem, and Alba having a smooth stem?
Not my call; folks with far more expertise than mine have made that call, and I don’t necessarily agree with it. To quote my detail page on the plant in question: “Many authorities (and, frankly, most folks who are not authorities) continue to consider Bidens alba a separate species from Bidens pilosa, and the plants on this page would be B. alba under those circumstances. As of January, 2012 the USDA plants database continued to maintain the separation of species, but the Integrated Taxonomic Information System (along with the Flora of North America) has adopted a more recent classification which rolls B. alba and B. odorata into B. pilosa. (I know that will be a disappointment to some.)” Here is a link to the pertinent page of the online Flora of North America, which lists Bidens alba as a synonym of Bidens pilosa – http://floranorthamerica.org/Bidens_pilosa