Senecio flaccidus, also known as threadleaf ragwort,[3] is a member of the daisy family. It is native from central to southwest North America, where it is common in gravelly and dry areas.
Description
Threadleaf ragwort is a fast-growing, short-lived (3 to 6 years) bushy perennial shrub growing to 4feet 6inches (1.37m) tall.[4] It is covered by a white close wool.[5] The stems are grooved and the branches are thin, herbaceous above and woody near the base.[6][4]
The leaves are 1 to 5 inches (2.5 to 12.7cm) long.[5] They are alternate and deeply pinnate, divided into five to nine narrow lobes. These are gray-green above and tomentose.[5]
From April to September appear showy yellow flowering heads,[5]3–4 inches (7.6–10.2cm) across. They have eight to thirteen sterile ray flowers, and purplish brown disk florets that produce the seeds.[4][7]
Seeds
Dicotyledon fruits; each a 1⁄8 inch (3.2mm)-long achene that is ribbed and hoary, covered with short white hairs.[6][4][7]
Taxonomy and names
The species was formerly recorded as Senecio douglasii (in honor of the botanist David Douglas).
The name threadleaf ragwort stems from the appearance of the leaves. Other common names include: threadleaf groundsel, bush senecio, creek senecio, shrubby butterweed, comb butterweed, smooth threadleaf ragwort, Mono ragwort, Douglas ragwort, Douglas groundsel, sand wash groundsel, felty groundsel, old man, yerba cana, squawweed, and cenicillo.
Subspecies
Senecio flaccidus Less. var. flaccidus
Senecio douglasii DC. var. longilobus (Benth.) L.D. Benson
Senecio douglasii DC. var. jamesii (Torr. & A. Gray) Ediger ex Correll & M.C. Johnst.
S.flaccidus can be found from the central to the southwestern United States, overlapping with the Great Plains region. It is native between Utah and Kansas, south to Arizona, New Mexico and Texas, and much of northern and central Mexico.
Like other members of its genus, it prefers disturbed habitats, especially overgrazed rangelands, dried-up streambeds and desert grasslands.[8] It can be found at altitudes between 1,800 and 6,500 feet (550 and 1,980m).[7] It is common in gravelly washes, dry creek beds, along roads and trails, and mostly away from the coast.[4]
Northern Mexico: Chihuahua, Coahuila, Durango, San Luis Potosí, Sonora, Zacatecas, Baja California
Central Mexico: Aguascalientes, Baja Norte, Guanajuato, Hidalgo, Jalisco (n.e.), Veracruz
Ecology
Colonizing disturbed areas including over-grazed lands, S.flaccidus helps to achieve a quick groundcover and helps to stabilize the soil for longer-lived perennials.
Toxicity
The species is poor forage for cattle and horses due to the alkaloids contained in the plant; these cause liver disease when consumed in large quantities.[8]
Also known as Senecio longilobus, one of the alkaloids found in this species is longilobine,[9] as well as senecionine, seneciphylline, florosenine, otonecine-based florosenine, and retrorsine.[8]
↑ Henderson FG, Harris PN, Chen KK (March 1951). "Liver injury following administration of alpha- and beta- longilobine". Proceedings of the Society for Experimental Biology and Medicine. 76 (3): 530–532. doi:10.3181/00379727-76-18545. PMID14844262. S2CID75269601. 14844262.
Arizona Vascular Plant Herbarium. "Senecio flaccidus". Southwest Environmental Information Network. Retrieved 20 February 2008.
Calflora. "Taxon Report – 7491". Information on California plants for education, research and conservation. www.calflora.org. Retrieved 20 February 2008.
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