Ironweed ‘Southern Cross’ (Vernonia hybrid)
Type: Perennial
Blooms: Purple flowers in late summer to early fall
Light: Full sun to part shade
Soil: Moist, well-drained but adaptable to dry or rocky soil
Pests: Powdery mildew, rust
Size: 30 to 36 in. tall and wide
Hardiness: Cold hardy in USDA zones 4 to 9
Attract wildlife with this cultivar of native vernonia
Grow ‘Southern Cross’ ironweed and in early to late fall you’ll enjoy its beautiful masses of fringed, bright purple flower clusters. And you’re not the only one: Bees and butterflies swarm the blooming plants for nectar, while deer and rabbits tend to pass it by. Once flowers fade, the spent blooms look attractive all winter. Be prepared to see more birds, who happily eat the seeds.
‘Southern Cross’ is a naturally occurring hybrid of native Vernonia species. At 3 feet tall with slightly wider leaves and a more compact habit than other ironweeds, it fits perfectly in a cottage garden or mini meadow without looking weedy. In fact, the fine-textured, lance-shaped foliage lends an airy look to a border, even when it’s not in bloom.
Pair late-blooming perennials with ironweed
Create a spectacular autumn floral display by combining ‘Southern Cross’ ironweed with other summer- to fall-blooming partners. Its purple flowers complement warm reds, oranges and yellows. Choose wildlife-friendly companion plants that attract bees, beneficial wasps, butterflies and birds, and watch the border come alive with color and movement.
Tips for growing ‘Southern Cross’ ironweed
- Grow ‘Southern Cross’ in full sun to achieve the best flowering and sturdiest plants.
- It’s clay-tolerant and once established, will also adapt to drought.
- Ironweed prefers lean soil, so there is no need to fertilize.
- To prevent powdery mildew and rust, don’t overcrowd this plant. Air movement between plants helps keep fungal diseases from getting established.
- Deadhead the plant to prevent possible reseeding, though ‘Southern Cross’ is less likely to have viable seed than the species.
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Plant a fall feast for pollinators
Create a spectacular autumn floral display by combining ‘Southern Cross’ ironweed with other summer- to fall-blooming partners. This plant combination provides nectar sources in autumn for migrating butterflies and other insects.
Growing conditions for this fall garden border with ironweed
The plants in this fall-peaking combination grow best in full sun. They'll tolerate dry conditions, but will thrive with an inch of water per week during the hottest part of the summer.
Plant care tips
- Leave spent ‘Southern Cross’ ironweed flowers on the plant. This cultivar is not likely to reseed in the garden, but does provide a food source for birds. Cut stems back in early spring.
- Tall sedum flowers dry brown and can stay standing all winter, providing color and interest. Shear off the dried stems in early spring as new growth emerges.
- Zinnia blooms all summer until frost. Deadhead faded flowers only if you want to tidy up the plant. Pull up zinnia plants after a hard frost and compost them.
A) Ironweed (Vernonia ‘Southern Cross’)
Perennial; purple flowers in late summer to early fall; full sun to part shade; 30 to 36 in. tall and wide; cold hardy in USDA zones 4 to 9
B) Tall sedum (Hylotelephium telephium ‘Purple Emperor’)
Perennial; pink flower clusters from midsummer to fall; purple-black foliage by summer; full sun; 12 to 15 in. tall and wide; cold hardy in USDA zones 3 to 9
C) Zinnia (Zinnia marylandica Zahara™ Yellow)
Annual; yellow flowers from late spring to frost; full sun; 12 to 18 in. tall and wide
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