Arizona Sneezeweed

Annuals, 30–70 cm. Stems usually 1, sparingly branched distally, weakly winged, glabrous or sparsely hairy. Leaves glabrous or sparsely hairy; blades all lance-linear, entire or coarsely toothed. Heads 1–15(–25) per plant, in paniculiform arrays. Peduncles 4–13 cm, glabrous or sparsely to moderately hairy. Involucres globoid to ovoid, 11–16 × 14–20 mm. Phyllaries sparsely to densely hairy. Ray florets 12–18, pistillate, fertile; corollas usually yellow, sometimes yellow with purple streaks, 10–20 × 5–13 mm. Disc florets 300–500(–700+); corollas yellow proximally, yellow to purple to dark blue-purple distally, 3.2–3.6 mm, lobes 5. Cypselae 2–2.9 mm, moderately hairy; pappi of 6–7 entire, aristate scales 1.5–2 mm. 2n = 30.

Helenium arizonicum is a North American perennial plant in the Sunflower Family, commonly known as Arizona sneezeweed. It is native only to Arizona in the southwestern United States, having been found only in four counties in that state: Apache, Navajo, Gila, and Coconino.

Helenium arizonicum is an annual herb up to 70 cm (28 inches) tall. One plant can produce as many as 25 flower heads, in branching arrays. The head is very nearly spherical or egg-shaped, nearly covered with as many as 700 disc florets, each floret yellow near the base but purple towards the tip. There are also 12-18 ray florets, yellow, sometimes with purple streaks. The species grows along the edges of wet places in pine forests.