Giant Ironweed Plant (Vernonia gigantea) Quick Facts!
Nectar plant for Monarchs, Swallowtails and many other butterflies.
Native to much of the eastern and southern US
Hardy in USDA zones 4-9
Full to partial sun
Prefers moist soil, but can tolerate most levels
Purple flowers blooms from July-Oct.
Grows about 5-8 feet tall
Space 1-2 feet apart
Seeds need 60 day cold stratification
Growing Giant Ironweed from seed:
Giant Ironweed seeds need 60 day cold stratification. You may sow in the Fall or artificially cold stratify the seeds prior to planting in the spring.
When ready to plant, choose an area that has full sun (some shade is OK). Since this plant will be very tall, consider the other plants in the garden. Barely cover the seeds with soil, no deeper than 1/8″. Keep soil moist, but do not overwater. Once the spring temperatures reach 65F, germination occurs in 2-3 weeks. Thin the plants (or space seedlings that were started indoors) to 18″ apart.
Giant Ironweed makes a great addition to a Butterfly Garden. Since it will be one of the tallest plants, you may want to place it in the back. It can be grown in large containers. It readily reseeds so if you have a small space, collect the seeds at the end of the season before the wind has a chance to spread them . To keep your plants healthy, divide every 3-4 years.