Vernonia gigantea (giant ironweed)

4 Photos

Summary

Four forms of the aptly named giant ironweed were included in the Vernonia trial. Three were determined to be top performers, including two examples of seed-grown plants from Alabama described here, and Vernonia gigantea ‘Jonesboro Giant’ which is discussed separately. Vernonia gigantea proved to be exceptionally adaptable to the average garden soils in the Trial Garden, displaying tall upright stems and clean disease-resistant foliage. The V. gigantea ecotypes from Alabama were among the last ironweeds to bloom, starting in late September and continuing through October and occasionally into early November. Approaching 12 feet in height, the towering inflorescences attracted some of the highest numbers of pollinators in the trial. Monarch butterflies were frequently observed on giant ironweed, and the peak bloom time of this species aligned with the southern migration of monarchs to the Sierra Madre mountains in Mexico. While the imposing stature of this species might rule out its use in smaller landscapes, V. gigantea is worthy of consideration where space allows.

Name	Rating	Height Range	Habit	Foliage Texture	Floral Display	Avg. Pollinators/Observation
Vernonia gigantea (AL ecotype, A)	4.2	9.5′ – 12′	upright vase	medium	good-excellent	3.27
Vernonia gigantea (AL ecotype, B)	4.4	9.5′ – 10.5′	upright vase	medium	excellent	4.94

Details

Rating
4.2 to 4.4 (Top Performers)
Common Name
giant ironweed