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Cardinal flower
Habit (mature) · Great Smoky Mountains National Park (photo by Warren Bielenberg) / Wikimedia Commons · Public domain (U.S. National Park Service work)
Limited coverage
Cardinal flower
Lobelia cardinalis
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.
Native: 42 US states
Review: Source-backed
Climate fit: broad (90/100)
Focal point
Pollinator
Border
Light
Full sun / Part sun / Part shade
Water
Consistent moisture
Mature size
24-48" tall · 18" apart
Hardy in zones
3a-9b
brutally cold to frosty winters
Summer heat range
Cool-Hot
cool to hot summers Interim Plotwright tier until the plant AHS range is authored.
Native in Illinois
Yes
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Heat and sun protection
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Native across 42 US states and Canadian provinces — a wide-ranging part of North America's plant communities.
Lady Bird Johnson Wildflower Center
Cold hardiness
Now
Zone 6b
USDA
Chicago, IL · 1991-2020 average annual coldest day
Source: USDA Plant Hardiness Zone Map 2023 (1991-2020 climatology) via ArcGIS FeatureServer
Well-suited
2050
Zone 7b
Plotwright
Your zone + climate-model shift · SSP3-7.0 (regional rivalry)
Well-suited
In plain terms: cold winters — coldest nights typically around -3°F.
Well-suited today and still thriving in 2050.
Heat tolerance
Loading current AHS heat-zone and plant heat-fit data at your coordinates…
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). Cardinal flower (Lobelia cardinalis). Retrieved 2026, June 5, from https://plotwright.garden/plants/cardinal-flower
Sources for every fact
Every fact on this page traces to a source. 18 fields cited18 source-backed.
Missouri Botanical Garden PlantFinder
Botanical research database
Backs 17 fields
Identity
Summary
Plant type
Light
Moisture
Hardiness
Heat zone
Size
Spacing
Habit
Design roles
Seasonal interest
Growth stages
Lifecycle
Regional guidance
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Designer notes
Wikimedia Commons
Photo · Public domain (U.S. National Park Service work)
Backs 1 field
Image
Community photos
The photos above are our reviewed reference set, curated for accuracy.
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