Melampodium divaricatum

Native from Mexico to Brazil, this plant is an annual herb of seasonally dry tropical regions. Its yellow flower heads combine petal-like ray flowers with a darker central disk of tiny florets. As older heads fade, the stems branch and produce more blooms. In temperate gardens, flowering continues from spring through autumn until frost. The dry, single-seeded fruits are cypselas, often called achenes, and the plant can self-seed under favorable conditions. Photographed in Colombia.