Description

Vernonia gigantea is the tallest of the ironweeds, and is also the species with the broadest native range. The rigid central stems can grow to a height of 9', or more under certain conditions. These are terminally branched and bear flat clusters of vibrant purple flowers. Although the individual flowers are small (only 1/4" across), they are borne on dense panicles up to 16" across. The alternate leaves are lance-shaped with finely toothed margins, up to 12" long by 2 1/2" wide, the top of which are dark green, whitish and pubescent on the undersides. The seeds are bullet-shaped, connected to small tufts of hair, and are easily distributed by the wind.

Cultivation

Giant ironweed is adaptable to a wide range of light and soil conditions. It tolerates the open shade of forest clearings and margins, as well as the full sun of open prairies and meadows so long as the soil does not dry out for extended periods of time. The root system is fibrous and rhizomatous, and will slowly spread to form dense clumps. The blooming period is long, up to 1 1/2 months, beginning as early as July and extending as late as September. Zones 5-9

Propagation

Can be propagated by root division when dormant. Seed germination rates are low, and those that are self-sown lose viability within 7 months.

Additional Notes

Vernonia gigantea is very attractive to nectaring insects and, given enough space, can be a stunning addition to a pollinator or rain garden. It is not palatable to mammalian browsers, and is highly deer resistant.