Sunflowers

Sunflowers

　　　　Sunflowers (xiangrikui) (Helianthus annuus), also known as helianthus flowers, belong to the Asteraceae family and the Helianthus genus. They are annual herbaceous plants, growing 1 to 3 meters tall. The stems are upright, sturdy, round, and multi-angled, covered with coarse white hairs. Leaves are usually alternate, heart-shaped ovate or ovate-round, with tips that are either sharp or gradually tapering, having three basal veins, with coarse serrated edges, both surfaces rough and hairy, and long petioles. The flower heads are very large, 10 to 30 centimeters in diameter, solitary at the top of the stem or branch tips, often nodding. The involucral bracts are multi-layered, leaf-like, arranged in an imbricate fashion, covered with long stiff hairs. They bloom in summer, with yellow ray florets around the edge of the flower head that are sterile. The central part of the flower head consists of bisexual tubular florets, which are brown or purple and fertile. The fruit is an achene, inversely ovate or ovate-oblong, slightly flattened, with a woody pericarp that is gray or black, commonly known as sunflower seeds. They prefer warm climates and are drought-tolerant. Native to North America, they are cultivated all over the world. The seeds are extremely high in oil content, flavorful, and can be eaten roasted or pressed for oil, making them an important oil crop. There are three types: edible, oilseed, and dual-purpose. The receptacle, stems, husks, and other parts can be used as industrial raw materials.