100 SWAMP SUNFLOWER (Narrowleaf Sunflower) Helianthus Angustifolius Flower Seeds BLOOM TIME: July - Aug HARDINESS ZONE: 3 - 9 PLANT HEIGHT: 24 - 66" . . . PLANT SPACING: 18 - 30" LIGHT REQUIREMENTS: Sun - Part Shade . . . SOIL / WATER: Average - Moist The Swamp Sunflower grows with small clusters of showy flowers and likes moist conditions. Attracts bees, butterflies, and birds.