Rush Bristleweed

Xanthisma junceum is reported from Arizona, but no specimen has been seen; as it is coastal in distribution, the report is likely based on a misidentified specimen.

Subshrubs, 25–100 cm; caudices branched, taproots 2–10+ cm. Stems 3–15+, branched in distal ¹ / 2 , slender and wiry, glabrous. Leaves: basal often withering by flowering, 20–35 × 6–12 mm, pinnatifid; cauline evenly spaced, blades oblong to linear, scalelike, 4–6 × 1–2 mm (except proximalmost), markedly reduced distally, margins usually entire, faces glabrous. Peduncles minutely glandular, if stipitate, then minutely so; bracts 5–25, imbricate, grading into phyllaries. Involucres hemispheric (narrowed at bases), 0.5–0.8 × 1–1.2 cm. Phyllaries in 5–6 series, oblong to linear-oblanceolate, 1.5–6.5 mm, apices acute, tipped by white bristle, faces minutely stipitate-glandular. Ray florets 15–25; corollas yellow, tubes 3.5–4 mm, laminae 5–6 × 1.5–2.5 mm. Disc florets 25–40+; corollas 4.8–6.3 mm. Cypselae narrowly obovoid to oblanceoloid, 1.5–2.5 mm, nerves 12–18, moderately tawny hairy; pappi tawny, 3.5–6 mm, a few abaxial bristles to ¹ / 3 of longest. 2n = 8, 16.

Haplopappus junceus Greene, Bull. Calif. Acad. Sci. 1: 190. 1885; Machaeranthera juncea (Greene) Shinners

Xanthisma junceum is a species of flowering plant in the family Asteraceae known by the common names rush bristleweed or rush-like bristleweed. It is native to northern Mexico and it occurs in the United States only as far north as San Diego County, California. It grows in coastal and inland slopes and canyons. It is a perennial herb growing erect to 1 m in height. The linear leaves are mostly located at the base of the plant, each 1–2 cm long and toothed or cut into bristle-tipped lobes. The inflorescence bears one or more flower heads lined with glandular, bristle-tipped phyllaries. The head has a center of many yellow disc florets and a fringe of 15 to 25 yellow ray florets each about 1/2 cm long. The fruit is a hairy achene 2–3 mm long tipped with a pappus.