Helianthus angustifolius, Swamp sunflower

Swamp sunflower
Helianthus angustifolius

Hardiness: Zones 5 to 9
Plant type: Herbaceous perennial
Height: 4- 5'
Spread: 4- 6' 
Sun: Full sun to part shade
Water: Wet
Bloom time: August to November
Bloom color: Yellow
Soil: Grows well in most soil from sandy to clay loam

Notes: Stems can be flimsy, plants may need to be staked, especially if planted in a windy location.  

More information on this plant here.