Arizona sunflowerweed

Tithonia palmeri Rose

Annuals, 70–200 cm. Leaves: petioles 0–3.3 cm; blades deltate, 7–28 × 5.5–21.5 cm, abaxial faces sparsely hirsute (hairs larger on veins). Peduncles 17–36 cm. Phyllaries 13–16 in 3 series, linear to spatulate; outer 8–15 × 2.5–4.5 mm, apices acute, abaxial faces puberulent; inner 12–15.5 × 3.5–7 mm, apices acute, abaxial faces glabrous. Paleae 11–16.5 × 2–4 mm, mucros 3 mm. Ray florets 7–10; corollas yellow, laminae oblong, 9–15 × 4–6 mm. Disc florets 40–60. Cypselae 6–9 mm. 2n = 34.

Flowering Aug–Sep. Disturbed areas, canyons, watercourses; 900–1000 m; Ariz.; Mexico (Sonora).