Duration: Perennial

Nativity: Native

Lifeform: Subshrub

General: Perennial herbs to subshrubs, 50-150 cm tall, stoutly rhizomatous and forming colonies; usually thorny proximally but often thornless above; stems green, erect; lateral branches sharply ascending, wandlike.

Leaves: Alternate, sessile, often early-withering; blades 1-nerved, oblanceolate, 1-4 cm long, the margins entire or rarely with 1-2 pairs of small teeth.

Flowers: Flower heads radiate, arranged in loose panicles; involucre (ring of bracts wrapped around the flower head) broadly turbinate to hemospheric, 4-6 mm high, the bracts (phyllaries) in 4-5 series, unequal, lanceolate, 3-nerved, with hyaline margins; ray florets 20-33, the laminae (ray petals) 4-7 mm, white; disc florets 20-70, the corollas yellow.

Fruits: Achenes fusiform-cylindric, slightly compressed, and 5-nerved, topped with a pappus of 30-60 persistent, tawny, barbellate bristles in 1-2 series, usually plus shorter outer bristles.

Ecology: Found in moist, saline soil, on riverbanks, bottomlands, saline flats, ditches, and irrigation channels, below 4,000 ft (1219) m; flowers May-October.

Distribution: CA and NV east to OK, TX, and LA; south through MEX to Costa Rica.

Notes: This large perennial has green herbaceous stems but behaves more like a subshrub, with the stems persisting year-round for several years. The leaves usually wither before flowering and colonies of this plant will then appear as masses of green, erect stems topped with loose, terminal panicles of small flower heads with white rays and yellow centers. Despite the species- name, many of the plants have very few thorns. The thorns are modified lateral branches and most often appear close to the base of the plant, though they can also be present above.

Ethnobotany: The Mojave roasted and ate the young shoots as a famine food; the Navajo chewed the stems like chewing gum.

Etymology: Chlorocantha from the Greek chloros, green, and akantha, thorn; spinose means spiny.

Synonyms: Aster spinosus, Erigeron ortegae, Leucosyris spinosa

Editor: AHazelton 2015

Stems 50-120(-150) cm, usually thorny proximally but armament of distal portions variable among populations, some producing only thornless, wandlike branches. Leaves mostly 10-40 mm. Involucres 4-5.5(-6) mm. Ray floret laminae 3.5-5(-7) mm. 2n = 18.

Flowering (May-)Aug-Nov. Riverbanks, freshwater swamps, bottomlands, low prairies, saline flats, ditches, irrigation channels; 0-1200(-1500) m; Ariz., Calif., La., Nev., N.Mex., Okla., Tex., Utah; Mexico.