Bidens cernua Linnaeus

Remark The words or terms in red (actually dark orange) in the text are defined in a glossary.


sep_15_05.jpg can't be loaded. Bidens cernua is an annual handsome herb, often bushy, native to North America, that is found in swamps, bogs and other humid locations. It is highly variable. Some botanists recognize two varieties: var. radiata that has ray-florets around the edge of the flower-head, and var. cernua lacking ray-florets and producing only disk-florets, the later one being the commoner and more widespread variety.

The plant belongs to the Asteraceae family.

Name

In Latin, bis means twice and dens means tooth so that bidens means two-toothed; hence the genus names refers to the bristles achenes of the plant, even if these seeds have, at times, three or four bristles.

The epithet cernua is from the Latin cernuus which means nodding, and refers to the quite often nodding flower heads of this species, this lowered posturing occurring somewhat more often in the literature than in nature!

Common names

Some of the vernacular names of Bidens cernua are: Bur marigold, Nodding Beggartick, Nodding Beggarticks, Nodding Beggar's Ticks, Nodding Bur Marigold, Nodding Burmarigold, Nodding Burr Marigold, Nodding Burr-marigold and Sticktight. The French vernacular name is Bident penché. The common names come from the tendency of the mature flowers to droop, from the clinging nature of the seeds, and the superficial resemblance of the yellow flower to the marigold. Walking through a stand of Bidens cernua plants in late summer or autumn results in numerous barbed nutlets adhering to the clothing.

Synonyms

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Identification

Bidens are well known for taxonomic taxonomic difficulty, the species having plastic phenotypes; Bidens cernua is rather variable. It can be identified by : When its ray florets are missing, Bidens cernua can be confused with Bidens connata and Bidens tripartita; however it differs from these species by its leaves, which are sessile or clasp and nearly surround the stem while those of Bidens tripartita and Bidens connata have distinct petioles that are winged or unwinged.

Description

Bidens cernua are low annuals, measuring between 1 and 4 feet in height, often branched, with the stems sometimes rooting at the proximal nodes.

Leaves

Flower heads

Fruits

Habitat

Bidens cernua is found around ponds and lakes, along streams, swamps, wet meadows, roadside and railroads ditches, marshes, bogs, and in areas of disturbed, degraded wet soils, although it also occurs in higher quality wetlands.

Distribution

map_na.jpg can't be loaded. Bidens cernua is found in most US States and Canadian provinces and territories; the exceptions are Newfoundland, Labrador and Nunavut in Canada, Florida, Mississippi and South Carolina in the USA. It is quite common in the north-east. The map shows the US States, Canadian provinces and territories where the plant can be found. It is also found in Eurasia where it is widespread.

Gallery

The photos of the gallery were taken either with one of the following: The title in the window shows the date when the picture was taken, i.e. jan_30_06... would mean that the photo was taken on the 30th of January, the 06 is for the 6th picture taken that day.

The month, day and picture number might be followed by a letter:

Click on the thumbnails to get larger view. The original photos are usually in TIFF format, the photos shown are generally in JPEG format, usually of dimensions one half (surface one quarter) for loading time reduction.

Plants

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Flower heads

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Seeds

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