Genus Information: In North America there are 71 species for Senecio. Worldwide, The Plant List includes 1,587 accepted species names and a further 871 scientific names of infraspecific rank for Senecio.
In the Southwestern United States: Arizona has 13 species of Senecio, California has 25 species, Nevada has 15 species, New Mexico has 22 species, Texas has 9 species, Utah has 18 species. Data approximate and subject to revision.
According to the Flora of North America, Senecio flaccidus var. flaccidus intergrades at least to some extent with var. monoensis in areas of overlapping ranges; a case could be made for treating the two as distinct species, as done by A. Cronquist (1994). Arizona varieties overlap.
Comments: The flowers of Threadleaf Groundsel and it's sub-species are too similar to use as a field identification characteristic.
Threadleaf Ragwort, variety flaccidus is a common large subshrub similar in appearance to Smooth Threadleaf Ragwort, Senecio flaccidus var. monoensis, but may be differentiated in the field where varieties overlap by its silvery or canescent woolly appearance and comb-like pinnatifid leaves.
The genus Senecio is known to contain alkaloids which may cause liver damage in livestock.
Importance to Wildlife, Birds and Livestock
Senecio flaccidus has large showy daisy-like flowers and the flowers and their seeds and plants may be visited by hummingbirds and/or small mammals including rodents and granivorous birds in search of food, nectar, shelter and protection through cover.
Beneficial Value to Butterflies, Bees and Insects
Senecio flaccidus has large showy daisy-like flowers and the flowers and their plants may be visited by butterflies, moths, native bees and other insects in search of nectar and/or other food.
The genus “Senecio” (Sene'cio:) from senex, "old man," referring to the gray hairs on the seeds.