Giant Sunflower (Helianthus giganteus)

Giant Sunflower

Helianthus giganteus

Giant Sunflower is a tall, robust perennial that can reach 4 to 10 feet in height. It thrives in wetlands, moist woodlands, and swamps preferring rich, moist soils. Its yellow blooms appear from late summer to fall, providing a crucial nectar source for bees and butterflies. Birds, especially goldfinches, feed on its seeds. It is well-suited for wildlife gardens and wetland restorations.

Characteristics

Product Form	Plant, Seed
Type	Forb
Sun	Full Sun, Partial Sun
Soil	Clay, Loam, Sand/Gravel, Peat, Calcareous
Moisture	Mesic, Wet
Average Max Height (inches)	80
Suggested Plant Spacing (inches)	24
Bloom month(s)	July, August, September
Bloom Color or Type	Yellow
Dominance	Medium

Range Maps

Sowing Information

Sow seed onto a firm, weed-free seedbed. Hand-broadcast seed making two perpendicular passes for even coverage. If planting a mix, broadcast the grass component first and lightly rake/drag it into the top 1/8–1/4" of soil. Next, broadcast wildflower/forb seed and press it into the soil surface (with a roller/cultipacker or the back of a rake) to ensure good seed-to-soil contact. After seeding, apply a very light layer of clean, seed-free straw (or other weed-free, site-appropriate mulch) to reduce erosion and retain moisture without smothering seedlings. A good rainfall or thorough watering will help settle seed and mulch and improve germination.

Planting Information

Dig a hole in your planting site slightly larger than the plant’s root system. When placing the plant into the hole, ensure that the soil line remains consistent with its original level in the pot. Fill in around the roots with the excavated soil, gently firming it to eliminate air pockets. Water the plant thoroughly the same day to promote successful establishment.