Senecio flaccidus var. flaccidus, Threadleaf Ragwort
Scientific Name: Senecio flaccidus var. flaccidus
Common Name: Threadleaf Ragwort
Also Called: Threadleaf Groundsel (Spanish: Hierba Ceniza)
Family: Asteraceae, Sunflower Family
Synonyms: (Senecio douglasii ssp. longilobus, Senecio douglasii var. jamesii, Senecio douglasii var. longilobus, Senecio filifolius, Senecio longilobus)
Size: Up to 3 feet.
Growth Form: Forb/herb, subshrub; erect; woody near base; herbage usually tomentose with white hairs but sometimes unevenly glabrescent.
Leaves: Green; alternate; margins pinnatifid, linear to filiform segments revolute.
Flower Color: Yellow; showy, ray flowers usually 8 florets; slender yellow, disk flowers yellow or orange-yellow, numerous; clusters with few to many heads on branch tips; "flower" heads weakly campanulate, fruit an achene.
Flowering Season: March to May or year-round if sufficient monsoon rainfall; June to November in Texas.
Elevation: 2,500 to 7,500 feet.
Habitat Preferences: Upper and lower desert, pinyon-juniper community, chaparral, mesas, slopes, dry washes, sandy or rocky soils and disturbed areas.
Recorded Range: Threadleaf Ragword is found mostly in the southwestern United States and in Colorado and Oklahoma; AZ, CO, NM, NV, OK, TX and UT. Also native to Baja California and northern Mexico.
North America & US County Distribution Map for Senecio flaccidus var. flaccidus.
U.S. Weed Information: No data available.
Invasive/Noxious Weed Information: No data available.
Wetland Indicator: No data available.
Threatened/Endangered Information: No data available.
Genus Information: In North America there are 70 species for Senecio. The Editors of Encyclopedia Britannica identify about 1,200 species distributed throughout the world.
In the Southwestern United States: Arizona has 13 species of genus, California has 25 species, Nevada has 15 species, New Mexico has 22 species, Texas has 9 species, Utah has 18 species. All data is approximate and subject to taxonomic changes.
Senecio flaccidus var. flaccidus is 1 of 3 varieties found in the southwestern United States:
Senecio flaccidus var. douglasii, Douglas' Ragwort (CA, CO, KS),
Senecio flaccidus var. flaccidus, Threadleaf Ragwort (AZ, CO, NM, NV, OK, TX, UT) and
Senecio flaccidus var. monoensis, Smooth Threadleaf Ragwort (AZ, CA, NM, NV, TX, UT).
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: 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.