COMPOSITE FAMILY COMPOSITAE 
TICKSEED SUNFLOWER. SWAMP MARIGOLD 
Bidens trichosperma (Michx.) Britton 
Thirteen species of Bidens are known to occur in Illinois 
and some of them are very similar and equally difficult to dis- 
tinguish. The genus is always identified by the persistent 
pappus of 2 or more awns either up- 
wardly or downwardly barbed, but 
only extremely detailed study will 
disclose the differences between 
species within groups of similar-ap- 
pearing flowers. 
They go by various names, such 
as Sticktight, Spanish Needles, De- 
vil’s Pitchforks, Beggar Ticks, Tick- 
seed and Bur Marigold. In some 
species the ray flowers are very in- 
conspicuous or absent, whereas in 
others, like the one illustrated, the 
rays are very showy. All bloom dur- 
ing the latter part of the season, 
from July or August to late autumn. 
The Tickseed Sunflower is one of 
the commonest and most showy 
Bidens. Often in September great 
areas of wet land, marshes and low 
meadows from Massachusetts to 
Georgia, Kentucky, [Illinois and 
Michigan are solid sheets of golden 
bloom of this or a closely related 
species. 
The stem is 2-5 feet high, much branched and smooth. The 
bracts of the involucre are in 2 series, the outer ones narrower 
than the inner. The receptacle is flat and chaffy. Ray and disk 
flowers are yellow. The pappus is 2 upwardly barbed awns. 
The Southern Tickseed Sunflower, Bidens coronata (L.) Fisch., and 
the Western Tickseed Sunflower, Bidens aristosa (Michx.) Britton, are 
considerably alike but the most noticeable difference is the hairy stems 
of the latter. The leaves of B. coronata are 3-divided, the terminal 
division much larger anr toothed or lobed. Those of the western 
plant are 5-7 divided and the segments are toothed, cut lobed or 
deeply divided. The upper leaves of both are small and may be un- 
divided or merely lobed. The heads of yellow flowers are 1-2 inches in 
diameter in both species but in the southern the outer bracts of the 
involucre are longer than the inner, whereas in the western sunflower 
they are not. The pappus of B. aristosa is 2, rarely 4, slender up- 
wardly or downwardly barbed awns sometimes as long as the mar- 
ginally fringed akene. In B. coronata it is 2 blunt and spreading teeth 
on the sparingly hairy but not fringed akene. 
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