Senecio flaccidus, formerly recorded as S. douglasii (in honor of the botanist David Douglas) member of the daisy family and genus Senecio also known as shrubby butterweed, comb butterweed, smooth threadleaf ragwort, Mono ragwort, Douglas ragwort, Douglas groundsel, sand wash groundsel, felty groundsel, old man, yerba cana, squawweed or cenicillo) is a native of the southwestern Great Plains of North America

This is a fast-growing, short-lived (3 to 6 years) bushy perennial shrub growing to 4 feet 6 inches (1.37 m); common in gravelly washes, dry creek beds, along roads and trails and mostly away from the coast.

Branched and bushy, S. flaccidus gets its common name from its white, threadlike, bent and matted, tomentose leaves; alternate and deeply pinnated, divided into five to nine narrow linear segments, glabrous, having no hairs or projections, gray-green above, 1 inch (2.5 cm) to 4 inches (10 cm) long. The principal leaves often have auxiliary clusters of smaller leaves. The stems are grooved and the branches are thin, herbaceous above and woody near the base.

Showy flowering heads of yellow ray flowers, 3 inches (7.6 cm) - 4 inches (10 cm) across; eight to thirteen sterile rays, purplish brown disk florets that produce the seeds.

Dicotyledon fruits; each a 1/8 inch (3 mm) long achene ribbed and hoary, covered with short white hairs.

Colonizing disturbed areas including over-grazed lands, Senecio flaccidus helps to achieve a quick ground cover and helps to stabilize the soil for longer-lived perennials but in this situation makes poor foraging for cattle and horses due to the alkaloids contained in the plant which cause liver disease when consumed in large quantities.

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