Aquatic and Wetland Vascular Plants of the Northern Great Plains

Bidens L. -- Beggarticks

Weedy annuals varying greatly in size and degree of branching. Leaves simple or ternately to pinnately compound, opposite, obscurely to coarsely serrate, sessile or petiolate. Heads discoid or radiate, the ray florets, when present, rather few, sterile or rarely pistillate, the ligules yellow; involucral bracts biseriate and dimorphic, the outer row usually foliaceous and spreading, the inner row short and erect, membranous, striate; receptacle flat to convex, chaffy, the chaffy bracts narrow, membranous, conspicuously few-nerved; disk florets perfect, numerous or sometimes few, the corollas yellow; style branches flattened, bearded above. Achenes flattened parallel to the involucral bracts, narrowed at the base and widening upward, more or less truncate at the apex, with a pappus of 2-4 retrorsely barbed awns which persist atop the achene, the achene body also barbed or stiffly appressed-hairy at least on the angles, the achenes commonly functioning as stick-tights in animal fur and clothing by means of the barbs.

References:

Fassett, N. C.  1925.  A key to the northeastern species of Bidens.  Rhodora
     27:184-185.  

Sherff, E. E.  1937.  The genus Bidens.  Publ. Field Mus. Nat. Hist., Bot. 
     Ser. 16:1-709. 

Weedon, R. R.  1973.  Taxonomy and distribution of the genus Bidens 
     (Compositae) in the north-central Plains States.  Unpubl. Ph.D. thesis, Univ. 
     Kans., Lawrence.

Lead	Characteristic	Go To
1	Leaves simple and toothed, some rarely incised or ternate.	Lead 2
1	Leaves all ternately or pinnately compound.	Lead 4
2	Achene margins barbed downward for their entire length.	Lead 3
2	Achene margins (and often the faces) barbed upward at least toward the base.	B. connata
3	Achenes with 4 awns; heads nodding after flowering (except on depauperate specimens).	B. cernua
3	Achenes with 3 awns; heads erect.	B. comosa
4	Rays well-developed and conspicuous, 1 cm or more long.	B. coronata
4	Rays absent or poorly developed and inconspicuous, less than 5 mm long.	Lead 5
5	Leaves pinnate-pinnatifid to bipinnate, the leaflets lobed; achenes with (2)3-4 awns.	B. bipinnata
5	Leaves pinnate or 3-foliate, the leaflets serrate; achenes with 2 awns.	Lead 6
6	Outer involucral bracts 5-10, typically 8; achenes dark brown to blackish.	B. frondosa
6	Outer involucral bracts 10-16 or more, typically 13; achenes olivaceous to yellowish, or occasionally brown.	B. vulgata

49. Asteraceae, the Aster Family

3. Bidens L. -- Beggarticks

1. Bidens bipinnata L. -- Spanish needles

2. Bidens cernua L. -- Nodding beggarticks

3. Bidens comosa (A. Gray) Wieg.

4. Bidens connata Muhl. ex Willd. -- Stick-tights

5. Bidens coronata (L.) Britt. -- Tickseed sunflower

6. Bidens frondosa L.

7. Bidens vulgata Greene

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