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 41 ecoregions — 40 climate-resilient through 2070 · 1 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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Atlantic coastal pine barrens

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Blue Mountains forests

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Canadian Aspen forests and parklands

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Central Pacific Northwest coastal forests

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Central Tallgrass prairie

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Central-Southern Cascades Forests

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Chilean Matorral

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What it needs

Conditions

Light

Full sun / Part sun / Part shade

Water

Consistent moisture

Spacing

18"

Habit

Erect, clump-forming native herbaceous perennial with terminal flower spikes

Care tips

•

Never let it dry out — site it in a rain garden, pond edge, or low spot, or commit to steady watering; drought is the usual killer.

•

Leave a few spent spikes to self-sow so the short-lived clumps replace themselves over the years.

•

In cold-winter climates, mulch the crown to prevent the shallow roots from heaving out of the ground over winter.

Lifecycle

Planting

Plant in spring or fall in rich, medium-to-wet soil in full sun to part shade. Needs constant moisture and will tolerate brief flooding; soils should never be allowed to dry out (Missouri Botanical Garden PlantFinder). In hot climates appreciate part shade; full sun is tolerated in cool, northern climates.

Transplanting

Move young plants or self-sown seedlings in spring while soil stays cool and moist; keep roots from drying during the move.

Early growth

Keep evenly wet through the first season to establish. Apply root mulch in cold-winter climates to protect the root system and prevent root heaving over winter, and to retain soil moisture.

Maturity

Mature plants reach 2 to 4 feet with erect terminal spikes of scarlet-red flowers from July to September. A somewhat short-lived perennial — allow some spikes to set seed so it can self-sow and persist in the planting.

Propagation

Propagate by seed (surface-sown, needs light to germinate), by division of the basal offsets, or by pinning stems down to root; allowing self-seeding is the simplest way to keep a stand going.

Pollination

Self-incompatible

Cardinal flower is functionally hummingbird-pollinated: its long, narrow scarlet tube is matched to the ruby-throated hummingbird, and the Lady Bird Johnson Wildflower Center notes the plant depends on hummingbirds — which feed on the nectar — for pollination because most insects cannot work the long tubular flowers. Like other lobelias it is protandrous (pollen is shed before the stigma of the same flower becomes receptive), which favors cross-pollination between flowers and plants.

Plants don't grow alone

Nectar forage

Specialist

Bird

Ruby-throated hummingbird (Archilochus colubris)

The scarlet, long-tubed flowers are shaped for the ruby-throated hummingbird, and the Lady Bird Johnson Wildflower Center documents the plant as depending on hummingbirds for pollination because insects struggle with the long tubular flowers — making this a keystone late-summer hummingbird nectar source.

Nectar forage

Bird

Baltimore oriole (Icterus galbula)

Nectar forage

Butterfly

Eastern tiger swallowtail (Papilio glaucus)

Missouri Botanical Garden PlantFinder lists cardinal flower as attracting butterflies; large swallowtails with long proboscises are among the few insects that can reach the nectar in the long red tube.

For people

Toxic — do not consume

Not a food plant. Missouri Botanical Garden notes the foliage contains alkaloids that are very toxic to humans if ingested. Grow it strictly as an ornamental and pollinator plant; keep its plant material away from anyone who might eat it.

Toxic parts

leaves, stems

Native range

Native across 42 US states.

AHS heat range

1-11

Native ecoregions

Naturally belongs in 30 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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Appalachian-Blue Ridge forests

›

Arizona Mountains forests

›

Atlantic coastal pine barrens

›

California coastal sage and chaparral

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Central Pacific Northwest coastal forests

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Central Tallgrass prairie

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Central-Southern Cascades Forests

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Chihuahuan desert

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Colorado Rockies forests

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Climate notes

•

Missouri Botanical Garden PlantFinder lists Lobelia cardinalis for USDA zones 3 to 9 in full sun to part shade with medium-to-wet moisture, blooming July to September; it tolerates rabbit, deer, and wet soil and is rated for naturalizing and rain gardens.

•

Missouri Botanical Garden notes the plant needs constant moisture and tolerates brief flooding but must never be allowed to dry out; in hot climates it appreciates part shade, while in cool northern climates it tolerates full sun.

•

The Lady Bird Johnson Wildflower Center documents Lobelia cardinalis (USDA symbol LOCA2) as native across 42 US states with habitat in ditches, stream banks, swamps, and woodland edges, and notes the plant depends on hummingbirds — which feed on the nectar — for pollination because insects struggle with the long tubular flowers.

In the designer

Growth over time

24-48" tall · 12-24" spread

Mature clump with full-height scarlet spikes; reseeds to persist as a short-lived perennial.

Design roles: Focal point · Pollinator · Border

Cardinal flower

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

Sources & citations