Swamp sunflower, perennial cousin to the popular annual sunflower (Helianthus annuus), is a stately specimen that reaches 6 feet more with flowers that may be on the small side at 2-3 inches, but it blooms for an extended period of time. Thin dark green leaves adorn coarse burgundy stems and showering sprays of mustard yellow blooms delight late summer through fall. These plants are beloved by birds, butterflies, bees, and other pollinators.
Due to its rapid growth, staking may be necessary to keep lose stems upright. Swamp sunflower provides a colorful backdrop for smaller late-season Aster, Sedum, and Salvia. True to its name, swamp sunflower performs well in boggy or swampy sites but may require additional watering when planted in dryer sites.
Quick Facts and Keys to Success
Common Name: Swamp sunflower or narrow-leaf sunflower
Botanical Name: Helianthus angustifolius
USDA Hardiness Zone(s): 6-9
Color: Golden yellow blooms.
Type: Flowering perennial providing interest late summer through fall.
Mature Size: 3-6 feet or more in height and width.
Exposure: Full sun for brilliant color
When to Plant: Spring or fall
How to Plant: Dig planting hole twice as large as root ball. Plant and backfill soil to natural grade.
Soil: Prefers moderately moist fertile soil. Tolerates boggy or swampy sites.
Watering: Water regularly, especially during drought periods.
When to Prune: Cut back by one-third in June to encourage a bushier plant. Discard spent foliage after frost and pruning to about 6 inches from the ground during dormancy.
When to Fertilize: Apply slow-release fertilizer in spring.
In Your Landscape: Massive perennial bloomer, filling a large garden space with golden yellow daisy-like fall blooms.