PL. —Vernonia missuricaBotanical illustration — drop image

Vernonia missurica

Missouri Ironweed

SummerFall

4a–8bHardiness zone

Peak bloom windowZone 6b · frost-offset weeks

Winter

Not in bloom

Spring

In bloom

Summer

Peak bloom

Fall

Not in bloom

Peak bloom

In bloom

Peak bloom windowZone 6b · frost-offset weeks

Winter

Not in bloom

Spring

In bloom

Summer

Peak bloom

Fall

Not in bloom

Peak bloom

In bloom

Background

Missouri ironweed (Vernonia missurica) is a native perennial of the central and east central United States, producing dense clusters of vivid magenta flower heads from late summer into fall. The tough, fibrous stems that give ironweeds their common name make this plant nearly self-supporting and persistent in the landscape.

It grows best in full sun with moderate moisture but adapts to average garden soils, including clay. Plants spread gradually by rhizomes and self-seeding, forming loose colonies in meadow and naturalistic plantings. Cutting stems back by one-third in late June reduces final height and limits flopping without eliminating the fall display. Near-neutral to slightly acidic soil pH and good organic matter content improve performance.

Missouri ironweed is a high-value late-season nectar source for monarch butterflies, painted ladies, bumblebees, and native bees. Goldfinches and other small birds forage on the seed heads through fall and winter, making it a strong choice for wildlife-focused plantings.

Good companions

Purple Coneflower Goldenrod Little Bluestem Boneset Joe Pye Weed Buttonbush Lobelias Rose Mallows

Care guide

SunFull sun to part shade

WaterModerate

SoilMoist, well-drained, clay-tolerant

Spacing24–36 in

Height3–5 ft

Zone4a – 8b

Native RegionAR, IL, IN, IA, KS, KY, LA, MI, MS, MO, OK, TX, WI

Direct sowFrost hardy

Seasonal tasks

spring

sowIf not fall-sown, start seeds indoors 6–8 weeks before last frost; surface-sow uncovered and keep at 65–70°F until germination.

sowTransplant seedlings to their permanent position after last frost date; space 24–36 in apart.

cutDivide established clumps every 3–4 years in early spring as new growth emerges to maintain vigor and manage spread.

summer

cutCut stems back by one-third in late June to reduce final height and limit flopping without sacrificing the fall flower display.

watchCheck foliage for rust pustules or leaf spot lesions; remove affected leaves promptly and thin crowded stems to improve air circulation.

fall

sowDirect sow seeds on the soil surface in fall after first frost; seeds require natural winter cold stratification to germinate the following spring.

cutDeadhead spent flower heads selectively to limit self-seeding; leave some in place to feed birds through winter.

Common problems

Fungal leaf spot

Symptoms

Brown or purplish spots on the leaves, often ringed with a yellow halo, that spread and merge in warm, humid, or wet weather; heavily spotted leaves yellow and drop early.

Treatment

Pick off spotted leaves and clear fallen debris to remove overwintering spores. Improve air circulation by thinning, and water at the base so foliage dries quickly. If it persists, apply a copper- or sulfur-based fungicide at the first sign.

Rust

Symptoms

Orange to brown raised pustules on the undersides of leaves, with yellow spotting on the upper surface. Heavy infections cause leaves to yellow and drop.

Treatment

Remove and destroy infected leaves. Avoid overhead watering and improve air circulation. Apply a sulfur or copper-based fungicide if it spreads. Clear plant debris in fall.

Powdery mildew

Symptoms

White or grey powdery coating on leaves — usually starting on older growth in humid conditions or when nights cool.

Treatment

Improve air circulation by thinning plants. Apply neem oil or potassium bicarbonate spray at first sign. Avoid overhead watering.