Giant Ironweed (Vernonia gigantea) Iron Weed Wildflower Wild Flower

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Giant Ironweed (Vernonia gigantea)


Height 1 to 3 m (3.3 to 9.8 feet)

Giant Ironweed is a herbaceous wildflower from the family Asteraceae, the Sunflower family, and is a perennial plant. This variety produces disk-like deep purple flowers shaped like flared tubes - each tube has 5 petals that are fused together at the bottom and separate out at the top. Each flower has a pistil (female part) and stamens (male part). After blooming, the seed heads turn rusty brown, hence the reason the plant is called ironweed as it is the color of rusted iron, while others suggest that the plant gets its name from its tough stems and long taproot.

About 17 species of ironweed are recognized in North America; this variety is native to the eastern United States, north to New York state and Ontario, and southwest to Texas. Stems are rigid and mostly smooth. Leaves are usually dark green and alternating - ranging from 4 to 12 in long, and 0.75 to 1.5 in wide and are smooth on top. Heads are typically in clusters of 10 to 20 at the end of branches and multiple branches may loosely overlap to produce flowering masses 4 to 7 in across. Each head has 15 to 25 individual purple disk flowers. 

Giant ironweed is found in prairies and other grasslands, old fields, roadsides, savannas and woodlands growing on dry to moist soils. Blooms mid summer to September. It is a strong competitor in the garden and spreads readily through self-seeding; keep in a container to control spread and/or manage spread by deadheading - snip off some of the flower heads before the seeds develop. Reducing the overall height of mature plants in late spring by cutting young stems back almost to the ground, and removing excess plants by division, will also keep it from spreading.

Traditionally, American Indians used ironweed for medicinal purposes, making teas from leaves to treat female problems, including relief from childbirth pain, and as a blood tonic. Root teas were used to treat loose teeth, and for stomach ulcers and hemorrhaging. The root of ironweed is a bitter herb, which means it can help to stimulate appetite and aid in digestion. Typically, it is prepared as a root powder or decoction (also known as tea) for this purpose. Giant Ironweed is an excellent nectar plant and is visited by many species of butterflies, bees and hummingbirds!

  • Full sun
  • Well draining soil
  • Start seeds indoors 4 to 5 weeks prior to last frost; plant no deeper than 1/8 in and barely cover with soil. Keep soil moist, but do not overwater.
  • NOTE: Some gardeners alternate refrigerating and freezing seeds to mimic winter conditions. To do this, put flats in the refrigerator for a day and then the freezer for a day. Follow this fridge/freezer process for a week before removing the flats to a warm room (70⁰F) to mimic spring weather OR alternatively, simply place the pots outside so they can experience the necessary cold stratification process (3 months min) at the start of winter. Seeds will germinate in the spring, and when the seedlings are at least 2 in tall, transplant into the garden when the spring temperatures reach 65 F.
  • OR DIRECT SOW seeds in the fall. Plant the seeds no deeper than ⅛ inch deep. Barely cover them with soil. The seeds will germinate in the spring. 
  • Spacing: 12 in apart.
  • Germination: 2 to 3 weeks
  • Harvest seeds: are the white fluffy part inside of the hardened flower petals after the plant has gone to seed. Carefully peel back the hardened outside covering of the flowerhead to expose the seeds. Keep them in a cool dark place until you are ready to plant them
  • Seed Count: 25