Cold hardiness

Future

2050

2100

These values are location-based: this location's current hardiness is the baseline, and the 2050 value is a projected future climate for this same location.

Now

Zone 6b

USDA

Published baseline for this location from 1991-2020.

Source: USDA Plant Hardiness Zone Map 2023 (1991-2020 climatology) via ArcGIS FeatureServer

Well-suited

2050

Zone 7a

Plotwright

Projected zone for this same location in 2050 (2041-2070) using SSP3-7.0 (regional rivalry).

Well-suited

In plain terms: This location is in Zone 6b today. Its hardiness profile is cold winters, and coldest nights are typically around -3°F. By 2050, the projected hardiness zone is Zone 7a based on SSP3-7.0 (regional rivalry). That is a +0.5-zone shift from Zone 6b to Zone 7a by 2050.

✓

Well-suited today and still thriving in 2050.

Heat tolerance

Future

2050

2100

Heat tolerance values are location-based too: heat days today are observed at this site, and the 2050 value projects this same location under a future climate.

Loading AHS heat-zone data for this location...

Where this plant fits

Suitable across 34 ecoregions — 26 climate-resilient through 2070 · 8 suited today. Best matches first.

Appalachian mixed mesophytic forests

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Appalachian-Blue Ridge forests

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Arizona Mountains forests

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Blue Mountains forests

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Canadian Aspen forests and parklands

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Central Tallgrass prairie

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Central-Southern Cascades Forests

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Colorado Rockies forests

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Cross-Timbers savanna-woodland

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Eastern Canadian Forest-Boreal transition

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What it needs

Conditions

Light

Full sun

Water

Consistent moisture

Spacing

24"

Habit

Erect, clumping tall herbaceous prairie perennial (3-6 ft)

Care tips

•

Give it steady moisture: site it in a low, wet, or irrigated spot and never let the soil dry out — this is a wet-prairie plant, not a drought-tolerant one.

•

Plant in full sun for the sturdiest, most upright stems; in shade or rich soil it stretches, flops, and blooms less.

•

For a shorter, bushier, self-supporting plant, cut the stems back by a third in late spring or early summer before bloom.

Lifecycle

Planting

Plant in spring in full sun in consistently moist to wet soil — this is a wet-prairie plant, so do not site it on dry, sharply drained ground where it will struggle. Rich, retentive loam, the edge of a pond or rain garden, or a low spot that holds water all suit it. Space about 24 inches apart to give the tall clumps room.

Transplanting

Move container plants in spring or early fall while the soil can be kept moist; established clumps have deep roots and transplant best when dormant. Keep new transplants well watered until they take hold, since drying out is the main early setback.

Early growth

Water consistently through the first season so the clump never dries out — steady moisture is what drives establishment. Plants put their energy into roots and foliage early and may not bloom heavily until the second or third year.

Maturity

Mature plants form a stiff, upright clump 3-6 feet tall that blooms in the second half of summer. In full sun with steady moisture the stems stand on their own; in part shade or after a flush of rich feeding they can lean and may need support or a midsummer cut-back.

Propagation

Propagate by seed — sow fresh in fall and let it cold-stratify over winter — or by spring division of established clumps. It self-sows modestly where soil stays moist and open, gradually thickening a planting.

Pollination

Self-fertile

The flat-topped clusters of small composite flower heads are insect-pollinated and set seed readily, drawing heavy late-summer traffic from native bees, bumblebees, and butterflies. Its bloom timing is its real value: it offers abundant nectar deep into the season, exactly when migrating monarchs and other late butterflies need fuel.

Plants don't grow alone

Nectar forage

Butterfly

Monarch butterfly (Danaus plexippus)

Late-summer Vernonia nectar is a well-documented fuel source for monarchs staging their southward fall migration.

Nectar forage

Bee

American bumblebee (Bombus pensylvanicus)

Vernonia is documented bumblebee forage; the open, nectar-rich clusters are worked heavily by native Bombus through late summer.

Nectar forage

Bee

Common eastern bumblebee (Bombus impatiens)

Nectar forage

Butterfly

Eastern tiger swallowtail (Papilio glaucus)

Large swallowtails nectar at ironweed's flat flower clusters; mapped as a representative late-summer butterfly visitor across the species' central-US range.

Nectar forage

Butterfly

Great spangled fritillary (Speyeria cybele)

Fritillaries are frequent visitors to native Vernonia in moist meadows; listed as a plausible nectar visitor rather than a recorded specialist tie.

Nectar forage

Butterfly

Skipper butterflies (Hesperiidae (family-level entry))

For people

Not eaten by humans

Grown strictly as a native pollinator and meadow ornamental — prairie ironweed has no established culinary use and is not eaten. It is not regarded as a notably toxic plant, but there is no reason to ingest any part of it; its value is in habitat and late-season color, not the table.

Native range

Native across 17 US states + 2 CA provinces.

Native ecoregions

Naturally belongs in 20 ecoregions — its native range crosses a state or province each one spans (not necessarily this exact habitat).

Appalachian mixed mesophytic forests

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Canadian Aspen forests and parklands

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Central Tallgrass prairie

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Chihuahuan desert

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Colorado Rockies forests

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Cross-Timbers savanna-woodland

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Eastern Great Lakes lowland forests

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Edwards Plateau savanna

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Flint Hills tallgrass prairie

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Mississippi lowland forests

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Climate notes

•

Established horticulture places Vernonia fasciculata at roughly USDA hardiness zones 3a-7b; it is native to the moist prairies, wet meadows, and streambanks of the central United States (Great Plains and Upper Midwest) and prairie Canada (this record consolidates the GBIF taxonomic backbone, Wikipedia, and USDA/BONAP range data rather than NC State's toolbox, which does not profile this prairie native).

•

A genuine wet-prairie species: it wants consistently moist to wet soil and full sun, and unlike drought-adapted prairie plants it does poorly on dry, lean, or sharply drained ground — chronic dryness, not cold, is its usual failure mode.

•

Cold-hardy well into zone 3 and adapted to hot, continental prairie summers, but it is not built for the hot, humid Deep South; the range tops out around zone 7, so it suits cool-to-warm climates far better than the hottest ones.

•

Largely free of serious pests and diseases in the open, sunny, moist conditions it prefers; powdery mildew or rust can appear on crowded or shaded stands, and leaf feeding by occasional caterpillars is cosmetic.

In the designer

Growth over time

36-72" tall · 24-36" spread

Mature 3-6 foot clump in full late-summer bloom, holding upright without staking where it gets enough sun and steady moisture.

Design roles: Pollinator · Structure

Seasonal interest

Spring

Summer

Fall

Winter

Filled = the plant has seasonal interest · ▾ now = your current season

Prairie ironweed

At a glance

Related products

Why it matters

Cold hardiness

Heat tolerance

Where this plant fits

What it needs

Lifecycle

Pollination

Plants don't grow alone

For people

Native range

Climate notes

In the designer

Seasonal interest

Sources & citations