Carnegiea gigantea, Giant Saguaro

Southwest Desert Flora

Home to the plants of the Sonoran, Chihuahuan and Mojave Deserts

Cirsium ochrocentrum, Yellowspine Thistle

Senecio flaccidus var. flaccidus, Threadleaf Ragwort

Threadleaf Ragwort like its sister Smooth Threadleaf Ragwort has showy bright yellow flowers that bloom from March to May or later with sufficient monsoon rainfall. Senecio flaccidus var. flaccidusThreadleaf Ragwort is of the genus Senecio which as a group have similar technical characteristics found in the phyllaries surrounding the “flower” head. One characteristic, difficult to see in the photo, is the black or dark spots on the pointed tips of the phyllaries. Senecio flaccidus var. flaccidusThreadleaf Ragwort is similar to Smooth Threadleaf Ragwort, Senecio flaccidus var. monoensis but its stems have whitish hairs over much of the stem while the latter is smooth, glabrous or without hairs. It is difficult to note the small whitish hairs in the photo. Senecio flaccidus var. flaccidusThreadleaf Ragwort has green, alternate pinnatifid leaves with thread-like revolute segments. The herbage is usually tomentose with white hairs but sometimes unevenly smooth or glabrescent. Senecio flaccidus var. flaccidusThreadleaf Ragwort is a native perennial sub-shrub found in the southwestern United States. Its preferred habitats include both upper and lower deserts, pinyon-juniper and chaparral communities often in dry washes, sandy or rocky soils and disturbed areas. Senecio flaccidus var. flaccidus

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)
Status: Native
Duration: Perennial
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.

In Southwest Desert Flora also see Lemmon's Ragwort, Senecio lemmonii, Smooth Threadleaf Ragwort, Senecio flaccidus var. monoensis and Common Groundsel, Senecio vulgaris.

The genus Senecio is known to contain alkaloids which may cause liver damage in livestock.

Date Profile Completed: 08/18/2012, rev 08/04/2014; Updated, 07/26/2015, updated 05/07/2017
References:
Arizona Flora, Kearney, Thomas H., Peebles, Robert H., 1960, University of California Press, Berkley and Los Angeles, as Senecio longilobus.
U.S. Dept. of Agriculture, Natural Resources Conservation Service on-line database and USGS ITIS search - (accessed 05/05/2017)
https://plants.usda.gov/java/stateSearch
Hosch, William L., Feb 15, 2008; The Editors of Encyclopædia Britannica; Access Date: May 05, 2017
https://www.britannica.com/plant/groundsel
Theodore M. Barkley, FNA | Family List | FNA Vol. 20 | Asteraceae | Senecio, 25a. Senecio flaccidus Lessing var. flaccidus; Flora of North America Editorial Committee, eds. 1993+. Flora of North America North of Mexico. 16+ vols. New York and Oxford.
Native Plant Information Network, NPIN (2013). Published on the Internet http://www.wildflower.org/plants/ [accessed: DATE 05/07/2017]. Lady Bird Johnson Wildflower Center at The University of Texas, Austin, TX.
http://www.wildflower.org/plants/result.php?id_plant=SEFLF
SEINet for synonyms, scientific names and recorded geographic locations, http://swbiodiversity.org/seinet/ [accessed: DATE 05/07/2017]