Common Name: ironweed
Type: Herbaceous perennial
Family: Asteraceae
Zone: 4 to 9
Height: 2.50 to 3.00 feet
Spread: 2.50 to 3.00 feet
Bloom Time: August to September
Bloom Description: Purple
Sun: Full sun
Water: Dry to medium
Maintenance: Low
Flower: Showy
Attracts: Butterflies
Tolerate: Drought, Dry Soil, Black Walnut
Culture
Vernonias native to North America are somewhat weedy herbaceous perennials commonly known as ironweed. They are easily grown in average, dry to moist, well-drained soils in full sun. Plants will naturalize in the landscape by self-seeding. Remove flower heads before seed develops to avoid any unwanted self-seeding. Plants of one species will commonly hybridize with plants of another species in the wild, resulting in the creation of fertile hybrids (usually intermediate in characteristics between the parents) which are often difficult to identify because hybridization obscures the lines that traditionally distinguish one species from another.
‘Southern Cross’ is not known to spread from seed as readily as other ironweeds.
Noteworthy Characteristics
Vernonia is a genus consisting of about 1000 species of herbaceous perennials, trees, shrubs and woody climbers found in tropical areas throughout the world and in temperate areas of North America, South America and Australia. About twenty of the species are native to the U.S., all being herbaceous perennials commonly known as ironweed. They typically feature composite flowers, each with fluffy, mostly pink-purple disks (rays absent), which bloom in loose, flattened clusters (corymbose cymes) from late summer into fall atop 2-10’ tall stiff stems clad with alternate, narrow-lanceolate, toothed or toothless leaves (to 4-8” long). Flowers give way to rusty clusters of fuzzy, bristly-winged seeds.
Genus name honors William Vernon (d. c. 1711), English botanist who collected in Maryland in 1698.
The source of the common name of ironweed has been varyingly attributed to certain “iron-like” plant qualities, including coarse foliage, tough stems, rusty-tinged fading flowers and rusty colored seeds.
‘Southern Cross’ is an ironwood hybrid (V. lettermannii is apparently in its parentage) that typically grows in a clump to 3’ tall and as wide. It features stiff upright stems clad with alternate, simple, narrow, linear to lanceolate leaves topped in fall by showy corymb-like cymes of bright purple flowers. Seed heads retain interesting shape after dispersal and persist well into winter.
Problems
Powdery mildew, rust and leaf spot may appear. Watch for slugs and snails on new growth.
Uses
Wild gardens, cottage gardens, or mixed border.