Growing Swamp Sunflower Plants: Helianthus Angustifolia Care

Helianthus Angustifolia  (hee-lee-AN-thus an-gus-tee-FOH-lee-us) is a native North American wildflower. Angustifolia grows freely in bogs, flood plains, and bottom lands throughout the eastern and southeastern United States. 

Flowering swamp sunflowerPin

This perennial wildflower is a member of the Aster or Asteraceae family. Its common name includes: 

  • Narrow-Leaved Coreopsis Sunflower 
  • Narrow Leaf Sunflower 
  • Swamp Sunflower

Swamp Sunflower – Helianthus Angustifolius Care

Size & Growth

Fast-growing Swamp Sunflower quickly attains a height of about 8’ feet tall. If you want smaller versions, there are some smaller cultivars to be had. 

Narrowleaf Sunflowers’ leaves are dark, glossy, and attractive. Stems are slightly hairy, and the leaves are long, narrow, and a bit scratchy. Individual leaves grow to be between 3”-6” inches in length. 

Flowering & Fragrance

Unlike standard sunflowers, Narrow-Leaved Coreopsis Sunflower produces multiple flower heads. Daisy-like blossoms are about two inches across and bright yellow with large, brown center disks. 

These wildflowers are late-bloomers and add a welcome splash of color yellow to the garden in mid-autumn. 

Light & Temperature

Swamp Sunflower can tolerate some shade but thrives in a full sun setting. These native plants are winter hardy in USDA hardiness zones 5 through 9.

Watering & Feeding

These eager growers are most vigorous in low-lying, boggy settings. They can grow in a drier environment, but they will not reseed themselves. 

Don’t fertilize Swamp Sunflowers because doing so can cause weak stems. 

Soil & Transplanting

The best soil for Swamp Sunflower is acidic, moist/occasionally wet, sandy, loamy, or even clay. 

Grooming & Maintenance

In June, perform a fairly aggressive pruning of your swamp sunflower to encourage more branches and more blooms. 

If plants grow too tall, and/or if your area gets lots of high winds, provide stakes for support. 

How To Propagate Swamp Sunflower – Helianthus Angustifolius

Sow seed directly into prepared, moist soil after all danger of frost has passed. Once established, the plant self-seeds enthusiastically.

Swamp Sunflowers Pests or Diseases

Beetles and caterpillars find leaves of Swamp Sunflowers quite tasty. But, these pests don’t usually cause serious harm. 

Because these plants do like a damp setting, fungal conditions such as leaf spot and powdery mildew can be problematic. 

Is The Swamp Sunflower Considered Toxic or Poisonous?

According to the ASPCA, Narrow-Leaved Coreopsis Sunflower is non-toxic for cats, dogs, and horses. 

Is The Swamp Sunflower Considered Invasive?

Swamp Sunflowers are native to the United States – therefore, not invasive. It grows freely in Florida marshes, wetlands, low lying ditches, and other boggy settings throughout the southeastern US.

Because it does reseed itself with wild abandon, many gardeners feel that it is invasive. The key to coexisting with it lies in accepting it for precisely what it is – an enthusiastic wildflower. [source]

Suggested Swamp Sunflower Uses

Narrow Leaf Swamp Sunflowers are the perfect choice for a wildscaped, naturalized, or pollinator garden. It is extremely popular with birds, bees, butterflies, and other desirable fauna. The caterpillars of these butterflies especially favor it:

  • Painted Lady butterflies
  • Gorgone Checkerspot
  • Silvery Checkerspot
  • Bordered Patch 

These beneficial pollinators are drawn to it: 

  • Pollinating Flies
  • Native Bees
  • Honey Bees
  • Butterflies 
  • Beetles 
  • Wasps

Songbirds, such as the American Goldfinch, also enjoy the seeds.

Swamp Sunflower is also a good choice for defining a back border, lining a stream bank, or surrounding a pond.

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