Giant Ironweed

Vernonia gigantea (ver-NOH-nee-ah jy-GAN-tee-uh)

Family: Asteraceae Native Herbaceous (3-15 ft)

Giant ironweed is a native herbaceous perennial wildflower in the Asteraceae or daisy family. This plant has a tall narrow habit that appears in the spring. The plant usually grows from 3 to 5 feet tall, but it has been known to grow to a height of 12 feet. Lavender, magenta, or deep purple flowers appear in late summer to early fall. The seeds are tiny achenes that have tufts of bristles that are easily dispersed by the wind. Giant ironweed is native to the southeast and the central United States and central Canada. It may be found naturally in prairies, grasslands, floodplains, woodlands, along roadsides, and near stream banks or forests edges. The plant is commonly found in overgrazed pastures. Livestock usually does not eat this plant resulting in the germination of the many seeds. The genus name, Vernonia, is in honor of an English botanist, William Vernon. The species name, gigantea , is Latin and means "of giants." The common name, ironwood, refers to the toughness of the stems of the plant. Giant ironweed prefers full sun to partial shade and well-drained moist to wet soils. They are tolerant of all soil pH and grow well in a mixture of loam, clay-loam, or sandy-loam soils. Cutting back the plant early in the season will reduce its height. Deadheading of the spent blooms will encourage continued flowering. This plant is easily propagated by seed or division. Native bees nest in the dead, hollow stems, so gardeners are encouraged to cut back dead stems to 12 to 24 inches and allow them to remain standing until they disintegrate on their own. Read more about best practices for stem-nesting bees in this NC Extension publication . The stem is tall, erect, stiff, and rounded. Atop the stem is a flat-headed panicle of flower heads that measures up to 16 inches across. Each flower head has 10-30 florets of lavender, magenta, or deep purple. Each floret is tubular that opens distally with 5 petals or lobes. The leaves are dark green on the upper surface and paler green and slightly hairy beneath. The fruits are grayish-brown achenes. Butterflies and bees are attracted to this pollinator plant. Most small mammals and livestock avoid it due to the bitter-tasting foliage. This native plant may be easily grown in a cottage garden, wildflower garden, or pollinator garden. Due to its height, it is best planted in the back of a border garden. It will compete with other plants in the garden and can become weedy if not controlled. Seasons of Interest: Bloom: Late Summer and Fall Foliage: Spring and Summer Fruits: Fall Quick ID Hints: tall, erect, stiff, rounded, green stem from 3 to 12 feet tall dark green ovate, oblanceolate to elliptical leaves, measuring up to 9 inches long and up to 2.5 inches wide with serrated margins atop central stem is a flat-headed panicle of flower heads of lavender, magenta, or deep purple that measure 6 to 16 inches in diameter each flower head has 10-30 florets that are tubular shaped fruits are gray to brown achenes with a tuft of short and long hairs Pests, Diseases, and Other Plant Problems: Giant ironwood has no serious problems with pests or diseases. Caterpillars of some moths may feed on the stems and roots of the plant. Aphids may be seen ingesting the juice of the stems and leaves. Crickets and katydids have been observed eating the flowerheads. VIDEO created by Andy Pulte for “Landscape Plant Identification, Taxonomy and Morphology” a plant identification course offered by the Department of Plant Sciences, University of Tennessee.

Source: NC State Extension Gardener Plant Toolbox ↗ NC State Extension Gardener Plant Toolbox, 64 attributes.