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Iris
Blue flag iris

Blue flag iris

Iris versicolor
A native eastern + central North American wetland iris producing striking violet-blue flowers with yellow + white throat markings in late spring + early summer. Tolerates wet feet better than most irises — among the best perennials for rain gardens, stream edges, and pond margins. Long-lived; clumps slowly expand. ALL parts of the plant are toxic (irisin glycoside) — wildlife typically avoid it; humans + pets can experience GI distress + skin irritation from sap contact.
Native: 29 US states + 1 CA province
Climate fit: broad (94/100)
Focal point
Pollinator
Light
Full sun / Part sun
Water
Consistent moisture
Mature size
24-36" tall · 18" apart
Hardy in zones
3a-9b
brutally cold to frosty winters
AHS heat range
1-11
Plant range authored in AHS heat-zone terms.
Native in Illinois
Yes

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Native across 30 US states and Canadian provinces — a wide-ranging part of North America's plant communities.

Cold hardiness

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
Plotwright
USDA Zone 6b
-5°F to 0°F
Well-suited
Zone 7a
Plotwright
0°F to 5°F
Well-suited
In plain terms: This location has cold winters. Its winters are projected to keep warming through 2050.
Well-suited today and still thriving in 2050.

Heat tolerance

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...

Similar plants

Browse lateral options with similar roles, light needs, size, or native-range overlap; these are not filtered for a better climate fit.
Lobelia cardinalis
Cardinal flower
A short-lived native perennial of wet woodland edges, stream banks, and ditches across the Americas, named for the brilliant scarlet-red flowers that rise on erect, unbranched terminal spikes from mid-to-late summer. Each tubular, two-lipped bloom is shaped for the hummingbird tongue — the plant depends on ruby-throated hummingbirds for pollination because most insects cannot work the long flower tube. It demands constant moisture and tolerates brief flooding, but its foliage carries alkaloids that are very toxic to humans if eaten.
Perennial
Full sun / Part sun / Part shade
Consistent moisture
Zones 3a-9b
Climate: broad
Focal point
Pollinator
Border
Vernonia noveboracensis
New York ironweed
A tall native eastern US perennial with deep purple-magenta flower clusters in late summer — among the most striking color in the native fall meadow palette. Tall and tolerant of wet feet; pairs visually with joe-pye weed + goldenrod for an iconic eastern wet-meadow trio.
Perennial
Full sun / Part sun
Consistent moisture
Zones 5a-9b
Climate: broad
Pollinator
Focal point
Eutrochium maculatum
Spotted Joe-Pye weed
A tall native northern + central North American perennial with whorled foliage on purple-spotted stems and broad rounded clusters of mauve-pink flowers in late summer. More cold-tolerant + moisture-loving than sweet Joe-Pye weed (E. purpureum); ideal for cold-climate rain garden + wet-meadow plantings.
Perennial
Full sun / Part sun
Consistent moisture
Zones 3a-8b
Climate: broad
Pollinator
Focal point
Eutrochium purpureum
Sweet Joe-Pye weed
A tall native perennial wildflower of moist meadows and woodland edges across eastern North America, producing large domed clusters of vanilla-scented pink-purple flowers in late summer — among the most reliable late-season nectar sources for monarchs, swallowtails, skippers, and native bees. Formerly classified as Eupatorium purpureum.
Perennial
Full sun / Part sun
Consistent moisture
Zones 4a-9b
Climate: broad
Pollinator
Focal point
Structure
Baptisia australis
Blue false indigo
A long-lived native perennial of central and eastern US woodland borders and prairie meadows with deep blue pea-shaped flowers in late spring, blue-green leguminous foliage, attractive black seed pods for winter interest, and a nitrogen-fixing root system (Fabaceae). Larval host for 6 documented butterfly species per NC State (orange sulphur, clouded sulphur, frosted elfin, eastern tailed-blue, hoary edge, wild indigo duskywing) — among the highest Lep-host-count perennials in the eastern flora.
Perennial
Full sun / Part shade
Moderate water
Zones 3a-9b
Climate: broad
Border
Pollinator
Focal point
Structure
Penstemon digitalis
Foxglove beardtongue
A native upright perennial of central + eastern North American prairies, woodland margins, and open woods producing tall vertical spires of white tubular flowers in late spring. The species name "digitalis" honors a flower-shape resemblance to true foxglove (Digitalis purpurea) — but Penstemon digitalis is NOT toxic in the same way (NC State explicit: "lacks the toxicity associated with foxglove"). Specialist Penstemon mason bee (Osmia distincta) relationship per NC State. The popular 'Husker Red' cultivar adds burgundy foliage for foliage-color design.
Perennial
Full sun / Part shade
Moderate water
Zones 3a-8b
Climate: broad
Pollinator
Border
Focal point

Sources & citations

Cite this page
For lesson plans, articles, or research that uses this page. To cite a single upstream fact instead, use its specific source listed below.
Plotwright. (2026, May 17). Blue flag iris (Iris versicolor). Retrieved 2026, June 24, from https://plotwright.com/plants/iris-versicolor
Sources for every fact
Every fact on this page traces to a source. 18 fields cited - 18 source-backed.
NC State Extension Gardener Plant Toolbox
University extension service
Backs 17 fields
Identity
Summary
Plant type
Light
Moisture
Hardiness
Heat zone
Size
Spacing
Habit
Design roles
Seasonal interest
Growth stages
Lifecycle
Regional guidance
Success tips
Designer notes
Wikimedia Commons
Photo · Public domain
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