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. monoensis, Smooth Threadleaf Ragwort

Smooth Threadleaf Ragwort has showy bright yellow flowers that bloom from March through May or later with sufficient monsoon rainfall. Senecio flaccidus var. monoensis Smooth Threadleaf Ragwort is of the genus Senecio which as a group have similar technical characteristics found in the phyllaries surrounding the “flower” head. One characteristic is the black or dark spots on the pointed tips of the phyllaries. Senecio flaccidus var. monoensis Smooth Threadleaf Ragwort is similar to Threadleaf Ragwort, Senecio flaccidus var. flaccidus but its stems are smoother, lacking surface hairs which are often found on the latter. Note the smooth or naked stems in the photo. Senecio flaccidus var. monoensis Smooth Threadleaf Ragwort is a native perennial found in the southwest United States in the upper and lower deserts in open areas, mesas, slopes, canyons, dry washes and sandy or rocky sites. Senecio flaccidus var. monoensis
Scientific Name: Senecio flaccidus var. monoensis
Common Name: Smooth Threadleaf Ragwort
Also Called: Green Groundsel, Mono Ragwort, Sand Wash Groundsel, Shrubby Butterweed
Family: Asteraceae, Sunflower Family
Synonyms: (Senecio filicifolius, Senecio lathyroides, Senecio longilobus, Senecio douglasii, Senecio douglasii var. monoensis, Senecio monoensis, Senecio pectinatus)
Status: Native
Duration: Perennial
Size: Up to 3 feet.
Growth Form: Forb/herb, subshrub, glabrescent or glabrous, slender branches.
Leaves: Green; alternate, glabrous; slender; margins entire, revolute, pinnately divided into narrow thread-like (filiform) segments; leaves up to 4 inches resemble a hair comb.
Flower Color: Yellow; showy, ray flowers 8 to 13; slender yellow, disk flowers yellow or orange-yellow, numerous; clusters with few to many heads on branch tips; phyllaries subtending flower head campanulate; fruit an achene.
Flowering Season: March to May or year-round with sufficient rainfall; April to June and September to November in California.
Elevation: 1,000 to 6,000 feet; 2,000 to 6,500 feet in California.

Habitat Preferences: Upper and lower desert, pinyon-juniper community, chaparral; open areas, mesas, slopes, canyons, dry washes, sandy or rocky sites.

Recorded Range: Native to southwestern United States in (AZ, CA, NM, NV, TX, UT), also in Baja California and northern and central Mexico.

North America & US County Distribution Map for Senecio flaccidus var. monoensis.

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. monoensis 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).
Arizona varieties overlap.

Comments: Smooth Threadleaf Ragwort, variety monoensis with its smooth, mostly glabrous features and comb-like pinnatifid leaves are key features that help to separate it from Threadleaf Ragwort, Senecio flaccidus var. flaccidus where varieties overlap. Senecio flaccidus var. monoensis intergrades with var. douglasii and with var. flaccidus in areas of range overlap.

In Southwest Desert Flora also see Lemmon's Ragwort, Senecio lemmonii, and Common Groundsel, Senecio vulgaris.

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

Date Profile Completed: 8/18/2012; Updated, 07/26/2015, updated 05/07/2017, updated format 10/11/2017
Arizona Flora, Kearney, Thomas H., Peebles, Robert H., 1960, University of California Press, Berkley and Los Angeles, as Senecio monoensis.
U.S. Dept. of Agriculture, Natural Resources Conservation Service on-line database and USGS ITIS search - (accessed 05/05/2017)
Hosch, William L., Feb 15, 2008; The Editors of Encyclopædia Britannica; Access Date: May 05, 2017
Katarina Andreasen & David M. Bates; Jepson Online Interchange, eFlora Treatment; (accessed )
Debra K. Trock 2017. Senecio flaccidus var. monoensis, in Jepson Flora Project (eds.) Jepson eFlora,, accessed on May 07, 2017.
Theodore M. Barkley † FNA | Family List | FNA Vol. 20 | Asteraceae | Senecio, 25c. Senecio flaccidus Lessing var. monoensis; Flora of North America Editorial Committee, eds. 1993+. Flora of North America North of Mexico. 16+ vols. New York and Oxford.
SEINet for synonyms, scientific names and recorded geographic locations,