Red Triangles

Centrostegia thurberi is fairly consistent morphologically throughout its range except for individuals in some populations in the mountains of the southern Coast Ranges that tend to have slightly longer and more robust involucres. The name var. macrotheca is available for such plants.

Plants 0.3-2(-3) × (0.6-)1-4(-5) dm. Leaf blades (0.5-)1-3.5(-4) × 0.3-0.8(-1) cm. Inflorescences: bracts mostly spreading, (1-)2-6(-10) mm; awns 1-2 mm. Involucres (2-)3-6(-8) mm; basal spurs with awns 0.2-2 mm; teeth flattened and keeled distally, awn erect, short, 0.3-1 mm. Flowers: perianth 2-3(-3.5) mm; tepals oblanceolate; filaments 1-3 mm; anthers 0.4-0.5 mm. Achenes 2-2.5 mm. 2n = 38.

Ariz., Calif., Nev., Utah; Mexico (Baja California, Sonora).

Flowering Mar-Jul.

Sandy to gravelly flats and slopes, mixed grassland, saltbush, creosote bush, and chaparral communities, pine-oak and montane conifer woodlands; 300-2400m.

Centrostegia thurberi var. macrotheca (J. T. Howell) Goodman; Chorizanthe thurberi (A. Gray) S. Watson; C. thurberi var. macrotheca J. T. Howell

Centrostegia is a monotypic genus of plants in the family Polygonaceae with a single species in the southwestern United States and northwestern Mexico. Centrostegia thurberi is known by the common names Thurber's spineflower and red triangles. It is a petite herb with a distinct red coloration.