A: Swamp Sunflower, Helianthus angustifolius, is a Florida native upright perennial potentially growing to heights of 4 feet or more. The dark green leaves are narrowly lanceolate and may reach a length of 8 inches. This spectacular fall bloomer bears yellow flowers with dark yellow or brown disks. In cold hardiness zone 8 seeds can be planted between May and July; for zone 9 planting times occurs April through August. Swamp Sunflower grows best in full sun to partial shade and can be planted in a well-drained soil although it is native to low wetland areas. It appears to have fairly good tolerance to planting in typical garden soil but benefits from some irrigation in dry weather. If grown in partial sun, pinch plants twice in early summer to encourage branching. Swamp sunflower responds well to regular applications of fertilizer. Many plantlets develop around the base of the Swamp Sunflower; divide it yearly to gain more plants. Propagate by seed. Swamp Sunflower is susceptible to powdery mildew and spittle bugs.