Wildflowers of the United States

Shepherd's Needles ,Spanish Needles, Romerillo, Common Beggar's-tick, Hairy Beggarticks, Cobbler's Pegs - Bidens pilosa

Genus Common Name: Beggarticks

Native Status: Native

Dicot Annual Herb

Bidens pilosa - Shepherd's Needles ,Spanish Needles, Romerillo, Common Beggar's-tick, Hairy Beggarticks, Cobbler's Pegs. Synonym: Bidens alba
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 Amertica) 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.) The USDA map shown does not include Missouri (as of January 2012), since if the species are considered separate B. pilosa is not found in the state, but B. alba is found there. That map also shows the plant as non-native. Bidens alba is considered native to parts of the United States. If that plant is considered a separate species, then Bidens pilosa is a non-native species. If Bidens alba is rolled into Bidens pilosa, then Bidens pilosa will need to be considered a native species in those areas where Bidens alba was considered to be native. That logic may be difficult to follow, but that's why I indicate B. pilosa to be a native species while the USDA map shows it to be introduced.

On a December, 2011 trip to Florida Shepherd's Needles seemed to become the dominant flowering plant along the highways by the time we got as far south as Gainesville. It seemed to be everywhere, and is officially considered a weedy or invasive plant in Hawaii, where it is not native. It's also considered weedy and invasive in much of the rest of the tropical world, where it has spread as man's travel has spread. While the plant may (probably will!) spread where it is not wanted, it is reported to be a great attractor for butterflies.

Found in:
AL, AZ, CA, CT, FL, GA, HI, KY, LA, MA, MD, MO, MS, NC, NM, OR, PA, SC, TX, WI

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Distribution of Bidens pilosa in the United States and Canada:

Map courtesy of The Biota of North America Program.
Map color key
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Site: Sarasota County, FL Date: 2011-December-18	Photographer: Gerald C. Williamson Nikon D7000
Bidens pilosa has 5 to 8 white ray flowers and many yellow disk flowers. Bidens species will more commonly have yellow ray flowers, and many have no ray flowers at all. Alba, the species epithet by which this plant is known in parts of the United States, means white. Because of this, I suspect Bidens alba will be used as the scientific name for this species for a long time to come, in spite of the more recent classification as part of Bidens pilosa.

Site: Sarasota County, FL Date: 2011-December-18	Photographer: Gerald C Williamson
Shepherd's Needles will have one to several blossoms terminating the many branches of the plant. It is erect when relatively young, but as the plant grows it will bow under its own weight, sprawling across the ground.
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Site: Sarasota County, FL Date: 2011-December-18	Photographer: Gerald C Williamson
Shepherd's Needles can flower year round in the southern reaches of its range.
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Site: Sarasota County, FL Date: 2011-December-18	Photographer: Gerald C Williamson
The seeds of Bidens pilosa are long and narrow with a pair of barbed points ("awns") that help them cling to clothing and fur, spreading them far and wide.
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Site: Sarasota County, FL Date: 2011-December-18	Photographer: Gerald C Williamson Nikon D7000
The petioled leaves are opposite with usually serrated margins, although the leaf may sometimes be entire. It is frequently pinnate with 3 to 7 lobes. As the plant grows, it frequently dips, sprouting roots at the nodes that touch the ground, resulting in a sprawling plant.
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References used for identification and information:

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Bidens pilosa initially published on USWildflowers.com 2012-01-15; Updated 2015-06-24

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All content except USDA Plants Database map Copyright Gerald C. Williamson 2024
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Code Update 20230302