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Cardinal Flower
Lobelia cardinalis
Cardinal Flower blooms from July through September.
Months here are Northern Hemisphere months; in the Southern Hemisphere, shift them by six months.
Growing Cardinal Flower
Plant it in part sun. It prefers high water. It is hardy in USDA zones 3–9. Expect it to reach about 3.5 ft tall and 1.5 ft wide at maturity, in roughly 2 years (not yet checked).
What was checked
Mature height and spread, hardiness zones, sun and the trait tags were checked against named botanical sources for this plant. The bloom months and water need on this page were not, and each fact above says which. The planting, spacing and size sections are derived from these checked facts by a fixed rule, not checked separately, and the plant type is the library's own classification.
When to plant Cardinal Flower
Plant Cardinal Flower in early spring as soon as the soil is workable, or in early fall at least six weeks before your first frost, so roots establish in cool weather. In zone 6, the middle of its hardy zones 3 to 9, spring means March to May and fall means August or September. Once settled, it blooms from July to September.
Month-by-month timing for your zone is on the planting calendar; if you garden near zone 6, the middle of this plant's hardy range, start with zone 6 in March. Derived from the plant's category, zones and bloom months plus typical zone frost dates, not checked separately.
How big does Cardinal Flower get?
3.5 fttall5 ft 7 inan adult1.5 ftwideSee Cardinal Flower in a garden plan: the planner shows it in 3D beside everything else you add, growing toward this size over the years.
How far apart to plant Cardinal Flower
Derived from the mature spread above by a fixed rule, not checked separately: spacing is the spread, center to center.
Space Cardinal Flower about 1.5 ft apart, center to center, so each plant has room to reach its full width.
Add Cardinal Flower to a garden plan and the planner draws it at its full width, so you see the spacing before you buy.
Where these facts come from
Cardinal Flower's height, spread, hardiness zones, sun and trait tags were checked against 11 published sources on July 30, 2026. Each one is linked below with every fact it carried, which can include a fact this page still marks as not yet checked, because a source carrying a value is not the same as the value being held to the standard. Facts not in that list, and the planting, spacing and size sections, are not covered by these sources.
- New Moon Nurseryheight, spread, hardiness zones, sun, years to mature size and trait tags
- Missouri Botanical GardenPlant Finderheight, spread, hardiness zones, sun and trait tags
- NC State ExtensionPlant Toolboxheight, spread, hardiness zones, sun and trait tags
- Mt. Cuba CenterNative Plant Finderheight, hardiness zones, sun and trait tags
- prairienursery.comPrairie Nurseryheight, hardiness zones, sun and trait tags
- RHSRoyal Horticultural Societyheight, spread, sun and years to mature size
- University of Maryland ExtensionHome and Garden Information Centerheight, sun, years to mature size and trait tags
- University of Wisconsin HorticultureUniversity of Wisconsin-Madison Division of Extension, Wisconsin Horti...height, hardiness zones, sun and trait tags
- Lady Bird Johnson Wildflower CenterNative Plant Databaseheight, sun and trait tags
- Missouri Department of ConservationField Guideheight, sun and trait tags
- Native Plant Trust (Go Botany)Native Plant Trust GoBotanyheight and trait tags
How the checking works, and what each standard covers, is on the verified plants page.
Good to know about Cardinal Flower
Curated from university extensions, botanic gardens and other primary sources, with the source named on every note. A note reports what its source says; where that differs from a fact above, the fact above is this entry's stored value, and its mark says whether it has been checked.
Safety
All parts are poisonous if eaten, from flowers to roots, holding lobeline-type alkaloids. Toxic to people, dogs, cats and horses; large amounts can be dangerous. per ASPCA and NC State
Worth knowing
The scarlet, nectar-rich tubular flowers depend on hummingbirds to pollinate them: insects struggle to navigate the long tube. Its late bloom fuels southbound migrating hummingbirds. per USDA and University of Illinois
How tall it gets
In average ground it stays 2 to 4 ft, but rich, constantly wet soil pushes the flower spikes to 5 or 6 ft. Plan spacing for your site. per NC State and Penn State
Keep the soil wet
It needs rich, constantly moist to wet soil and must never dry out: a streambank, pond edge, or rain garden suits it well. Drought kills it. per NC State
Deer and rabbit resistant
Deer and rabbits leave it alone, so it can persist even where browsing is heavy. The same toxic alkaloids that poison make browsers avoid it. per Wisconsin
Short-lived; renew it
It is a short-lived perennial. To keep a stand going, let some seed drop (the tiny seed needs light, so don't bury it) and divide the rosettes. per Wisconsin
Nicknamed Indian tobacco
Its main alkaloid, lobeline, acts on the same nicotine receptors tobacco does, so Lobelia earned the name Indian tobacco and was once used as an emetic. per Molecules
What pairs well with Cardinal Flower
Good companions share its growing conditions and add something it lacks: an earlier or later bloom, a lower carpet in front, or structure through winter.
Rhododendron
Takes part sun to part shade and moderate to high water; blooms in late spring, before this one opens; both are strong pollinator plants, and they feed in different months; evergreen, so the bed keeps its shape through winter.
English Daisy
Takes full sun to part sun and moderate to high water; blooms in mid spring, before this one opens; low at 6 in, to carpet the ground beneath; both offer pollinator forage, in different months.
Winterberry
Takes full sun to part sun and high water; blooms in mid fall as this one finishes; both are strong pollinator plants, and they feed in different months; both are North American natives.
Snowdrop
Takes part sun to part shade and moderate to high water; blooms in late winter, before this one opens; low at 5 in, to carpet the ground beneath; both are strong pollinator plants, and they feed in different months.
Chives
Takes full sun to part sun and moderate to high water; blooms in late spring, before this one opens; both are strong pollinator plants, and they feed in different months; lower at 12 in, for the front of the border.
White Clover
Takes full sun to part sun and moderate to high water; opens in late spring and overlaps into this one's season; low at 4 in, to carpet the ground beneath; both are strong pollinator plants.
Aster
Takes full sun to part sun and moderate to high water; overlaps, then carries the display into mid fall; both are strong pollinator plants; its seed heads stand through winter, for structure and the birds.
Pansy
Shares part sun and moderate to high water; blooms in early spring, before this one opens; lower at 8 in, for the front of the border; both offer pollinator forage, in different months.
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Drop this plant onto a 3D plan, see how it fills in, and watch your whole garden bloom across the year.