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. flaccidus Threadleaf Ragwort is of the genus Senecio have similar technical characteristics found in the bracts (phyllaries) surrounding the head. One characteristic, difficult to see in the photo, is the black or dark spots on the pointed tips of the bracts. Senecio flaccidus var. flaccidus Threadleaf Ragwort has 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 a cypsela. Senecio flaccidus var. flaccidus Threadleaf 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. flaccidus Threadleaf 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 (91 cm) or more.

Growth Form: Forb/herb, subshrub; plants upright (erect); woody bases; herbage tomentose with white hairs, sometimes unevenly glabrescent.

Leaves: Green; leaves arranged alternately along stems; leaves linear to filiform or pinnatifid.

Flower Color: Yellow; large and showy; flower heads on tips of branches, 1 or many in clusters; flower head with both ray and disk florets; fruit is a cypsela.

Flowering Season: March and April to July and August; year-round with sufficient rainfall; June to November in Texas.

Elevation: 2,500 to 7,500 feet (762-2,286 m).

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 in AZ, CO, NM, NV, OK, TX, UT. This variety is also native to central and northern Mexico.

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

North America species range map for Threadleaf Ragwort, Senecio flaccidus var. flaccidus:

North America species range map for Threadleaf Ragwort, Senecio flaccidus var. flaccidus: Click image for full size map.
Click image for full size map

U.S. Weed Information: Unknown
Invasive/Noxious Weed Information: Unknown
Wetland Indicator: Unknown
Threatened/Endangered Information: Unknown

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.

The genus Senecio was published in 1753 by Carl Linnaeus, (1707-1778).

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.

There are 3 varieties in Senecio flaccidus;
Senecio flaccidus var. douglasii, Douglas' Ragwort (CA, CO, KS);
Senecio flaccidus var. flaccidus, Threadleaf Ragwort (AZ, CO, NM, NV, OK, TX, UT);
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: The flowers of Threadleaf Groundsel (Senecio flaccidus) 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.

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

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

Importance to Wildlife, Birds and Livestock
Senecio flaccidus var. 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 var. 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.

Etymology:
The genus “Senecio” (Sene'cio:) from senex, "old man," referring to the gray hairs on the seeds.

The genus Senecio was published in 1753 by Carl Linnaeus, (1707-1778).

The species epithet “flaccidus” (flac'cidus:) is Latin for flaccid.

Ethnobotany
Unknown

Date Profile Completed: 08/18/2012; updated 10/25/2020
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 10/25/2020.
https://plants.usda.gov/core/profile?symbol=SEFLF
The Plant List (2013). Version 1.1. Published on the Internet; http://www.theplantlist.org/; accessed 10/25/2020.
http://www.theplantlist.org/1.1/browse/A/Compositae/Senecio/
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: 10/27/2020]. Lady Bird Johnson Wildflower Center at The University of Texas, Austin, TX.
http://www.wildflower.org/plants/result.php?id_plant=SEFLF
Seiler, John, Peterson, John, North American species range map courtesy of Virginia Tech, Dept. of Forest Resources & Environmental Conservation
http://dendro.cnre.vt.edu/dendrology/
SEINet synonyms, scientific names, geographic locations, general information.
http://swbiodiversity.org/seinet/
Etymology:Michael L. Charters California Plant Names: Latin and Greek Meanings and Derivations; A Dictionary of Botanical and Biographical Etymology - (accessed 10/24/2020)
http://www.calflora.net/botanicalnames/pageSA-SH.html
http://www.calflora.net/botanicalnames/pageF.html
IPNI (2020). International Plant Names Index. Published on the Internet http://www.ipni.org, The Royal Botanic Gardens, Kew, Harvard University Herbaria & Libraries and Australian National Botanic Gardens. [Retrieved 25 October 2020].
https://www.ipni.org/?q=Senecio