FIRST IMPRESSIONS: Helianthus decapetalus is an upright rhizomatous perennial wildflower. The attractive leaves are oval to lance shaped and dark green with sharply serrated edges. From mid-summer until autumn, golden 3” daisies grace the plant and entice bees, butterflies and other pollinators. This sunflower thrives in difficult wet shady sites or in gardens with dappled shade and average garden soil.
HABITAT & HARDINESS: Helianthus decapetalus occurs in Quebec, Ontario and from Maine to Georgia and west to Wisconsin and Louisiana.
Habitats include wet open woods, woodland clearings and borders, partly shaded banks of rivers or streams, savannas, meadows and thickets.
Plants are hardy from USDA Zones 4-9.
PLANT DESCRIPTION: Helianthus decapetalus is an attractive woodland sunflower with smooth green, reddish or purple stems.
Leaf arrangement varies with the lower leaves being opposite and upper leaves alternate. The blades are thin and pliable and up to 7” long. They are widely lanceolate or ovate with sharp teeth. The leaf base narrows abruptly into a long winged stalk or petiole.
Stems terminate in numerous 3” flowerheads held on long leafless stalks. The heads consist of 8-12 oblong yellow rays surrounding a cluster of golden disc flowers.
Dark clusters of achenes form after flowering.
Plants grow up to 5’ tall with 3’ spread. They often form colonies from underground rhizomes.
CULTURAL & MAINTENANCE NEEDS: Helianthus decapetalus is easy to grow in sun to part shade with dry, well drained, moist or wet soil.
This species grows best in an evenly moist soil but will tolerate a bit of drought after establishment. Powdery mildew may be problematic if plants are stressed by long periods of drought.
Stems are likely to become weak if plants are fertilized. Pruning in spring encourages branching, stronger stems and denser growth.
Plants form colonies from self-seeding and from underground rhizomes.
Plants are pest resistant but are occasionally nibbled by rabbits, deer or livestock.
LANDSCAPE USES: This is a good choice for a Wildlife Garden or Meadow. Plants are also used as Butterfly Nectar Plants, Butterfly Host Plants or as part of a Grouping or Mass. Helianthus decapetalus has Showy Blooms and is appropriate for Cottage Gardens, Deer Resistant Plantings, Rain Gardens, Water-wise Landscapes, Low Maintenance Plantings, Perennial Borders and Roadsides.
COMPANION & UNDERSTUDY PLANTS: Try planting a shady rain garden with Helianthus decapetalus and Chelone glabra, Dryopteris marginalis, Iris versicolor, Luzula acuminata, Phlox maculata or Senecio aureus.
Helianthus divaricatus could be substituted in some situations. The two have similar flower apprearance and cultural requirements.
TRIVIA: The flower nectar and pollen appeals to honey bees, native bees, beneficial wasps, pollinating flies, butterflies, skippers and beetles. At least 6 species of specialty bees (that only pollinate Helianthus spp.) visit the flowers. Helianthus decapetalus hosts caterpillars of checkerspot butterflies. painted lady butterflies and several moths. Seeds are eaten by gamebirds, songbirds and small mammals. Mature colonies provide good cover for many kinds of wildlife.
Muskrats are reported to feed on the foliage and use the stems in the construction of their lodges.
Helianthus decapetalus can be differentiated from similar species by several unique leaf characteristics. The blade margin has unusual sharp teeth. The blade tip is exceptionally long and slender. The blade base narrows abruptly into a long winged petiole.
For more information on this plant, visit the USDA PLANTS Database: http://plants.usda.gov/java/profile?symbol=HEDE