Amerikanhelosäde

Nile region (Aswan), oases (Kharga) and Sinai (El Arish).

Native to south and central America, naturalized in many regions of the Old World, pantropical weed.

Waste ground, roadsides, edges of cultivation.

Annual.

Native distribution of Verbesina encelioides in the flora area is uncertain. Plants of Verbesina encelioides from ca. 100°W (e.g., c Texas) and eastward usually have auriculate petiole bases and have been called var. encelioides; plants from the west usually lack auricles and have been called var. exauriculata.

Plants 10–50(–120+) cm (annuals, internodes not winged). Leaves all or mostly alternate (proximal usually opposite); blades deltate-ovate or rhombic to lanceolate, 3–8(–12+) × 2–4(–6+) cm, bases broadly cuneate to ± truncate, margins coarsely toothed to subentire, apices acute to attenuate, faces strigoso-scabrellous to sericeous. Heads usually borne singly, sometimes 2–3+ in loose, cymiform or corymbiform arrays. Involucres ± hemispheric to saucerlike, 10–20+ mm diam. Phyllaries 12–18+ in 1–2 series, ± erect to spreading, lance-ovate or lance-linear to linear, 6–8+ mm. Ray florets (8–)12–15+; laminae 8–10(–20+) mm. Disc florets 80–150+; corollas yellow. Cypselae dark brown to blackish, narrowly obovate, 3.5–5+ mm, faces ± strigillose; pappi 0.5–1(–2) mm (0 on ray cypselae). 2n = 34.

Ximenesia encelioides Cavanilles, Icon. 2: 60, plate 178. 1793 (as enceliodes); Verbesina encelioides subsp. exauriculata (B. L. Robinson & Greenman) J. R. Coleman; V. encelioides var. exauriculata B. L. Robinson & Greenman

Annual herb up to 1 m tall. Stems ribbed, hairy. Leaves mostly alternate, sometimes opposite, ovate-triangular, up to 10 × 7 cm, 3 veined from the base, with appressed greyish hairs, particularly below, discolorous; margin irregularly toothed. Petiole irregularly winged and auriculate on the stem. Capitula solitary at the ends of branches, c. 2.5 cm in diameter. Rays bright yellow, elliptic-obovate, c. 1 cm long, 3-toothed at the apex. Involucral bracts up to 1.3 cm long, linear, appressed greyish hairy.

Native to Southwestern USA and Mexico; introduced into West Indies, tropical Africa and northern S Africa.

Chile Central

Verbesina encelioides is a flowering plant in the family Asteraceae. The species is native to many parts of the United States and Mexico. It is naturalized in other parts of North America, the Middle East, Spain, Argentina, Australia and the Pacific islands. Common names include golden crownbeard, gold weed, wild sunflower, cowpen daisy, butter daisy, crown-beard, American dogweed and South African daisy.

The species responds strongly to disturbances on suitable sites and retards the development of other local species. Research has identified an allelopathic effect on radishes which may explain its ability to dominate other species in some locations.

It is a larval host for the bordered patch.

Verbesina encelioides là một loài thực vật có hoa trong họ Cúc. Loài này được (Cav.) Benth. & Hook.f. ex A.Gray miêu tả khoa học đầu tiên năm 1876.