Cardinal flower
Lobelia cardinalis · Campanulaceae
Spikes of the most intense scarlet in the garden, in late summer, pollinated almost entirely by hummingbirds. It grows wild on stream banks and needs wet soil.
- Size
- 3½ ft tall, 16 in wide
- Zones
- 3 to 9
- Light
- Full sun to part shade
- Flowers
- Late July to mid September
- Pets
- Toxic (moderate)
- Job in a bed
- Accent
A bed built around cardinal flower
The planner designed this bed around cardinal flower when this page was made: a 12 × 6 ft (3.7 × 1.8 m) cottage garden in zone 6, part sun. It chose the other plants from the 367 that suit those conditions and its wet soil, and says below why cardinal flower stands where it does.
The plants
- 1 Cardinal flower × 4, red
- 2 Spotted dead nettle × 6, pink
- 3 Drumstick primrose × 5, lavender
- 4 Rose turtlehead × 3, pink
- 5 Globe arborvitae 'Danica' × 1, green leaves
- 6 Japanese anemone 'Honorine Jobert' × 5, white
- 7 Quamash × 12, blue
- 8 Snowdrop × 12, white
Why this plant
- A classic partner for rose turtlehead. Both are on this plan. A pairing gardeners have proved outranks a general rule.
- The only red. The one hot colour: every other flower here is cool or neutral.
Why here
- Anchors a back corner. At 3½ ft it is among the tallest plants here, and the tallest close the ends of the bed, where they stand in front of nothing.
- A step in the back row. Next to rose turtlehead (2½ ft): no two neighbours there are the same height, so the back steps up and down like a skyline.
- 4 plants in 2 places. An accent is a punctuation mark: the repeat along the bed gives it rhythm.
Why now
- In flower for 8 weeks. From late July to mid September.
- Fills a gap. For three of those weeks nothing else on the plan is in flower.
Planned as a cottage garden: 24 of the 24 plants (100%), bulbs aside, stand alone or in groups of no more than five, small enough for the kinds to mingle. Cardinal flower and Japanese anemone 'Honorine Jobert' anchor the back corners of the bed: the tallest plants on the plan stand there. It is planted in layers: about 12 in at the front, 16 in in the middle and 2½ ft at the back.
The planner's own design check: 11 Excellent, 5 Good, 1 Satisfactory. It flags one thing to watch: Nothing on this plan is highly poisonous or an aggressive spreader.
Open this bed in the planner Change its size, the sun or the style, move plants about, or swap one for another.
Where cardinal flower goes in a border
At 3½ ft it belongs at the back of a bed. In the planner's ten height classes it is moderately tall (3 to 4 ft).
Its job: accent. An upright plant used singly, like a punctuation mark, and repeated at intervals to give the bed rhythm.
Pure red that glows in shade. Each plant lives only a few years, so let it seed, and keep mulch and fallen leaves off the winter rosettes. Wonderful with great blue lobelia.
- Rain gardens and pond edges
- Hummingbird gardens
- Red vertical accents in part shade
What to plant with cardinal flower
Plants recorded as good partners for it, and what each pairing does:
- Great blue lobelia: in flower together for six weeks, from early August.
- Swamp milkweed: in flower together for three weeks, from late July.
- White turtlehead: in flower together for six weeks, from early August; happy in the same wet soil.
Questions about cardinal flower
Does cardinal flower need sun or shade?
Cardinal flower grows in full sun (6 or more hours of direct sun a day), part sun (4 to 6 hours of sun, including some afternoon sun) and part shade (2 to 4 hours of sun, mostly in the morning).
It wants moist to wet soil, rich in organic matter, and plenty of water. It copes with soil that stays wet.
What zones does cardinal flower grow in?
USDA zones 3 to 9. It is hardy to zone 3, which means it survives winter nights down to about −30 °F (−34 °C).
Gardening in Canada? Use the USDA zone for your town: Canada's own zone map uses different numbers.
When does cardinal flower flower in my zone?
In zone 5 it flowers late July to mid September. As a summer flower it moves about half a week for every zone: earlier where it is warmer.
| Zone 3 | Early August to mid September |
|---|---|
| Zone 4 | Early August to mid September |
| Zone 5 | Late July to mid September |
| Zone 6 | Late July to mid September |
| Zone 7 | Mid July to mid September |
| Zone 8 | Mid July to mid September |
| Zone 9 | Mid July to mid September |
Worked out from Hopkins' bioclimatic law: spring arrives about four days later for each degree of latitude north, and one zone is roughly two degrees. A warm spring or a cold one moves any garden two weeks either way.
How far apart should cardinal flower be planted?
14 in (35 cm) apart, from the middle of one plant to the middle of the next. That is a little closer than its full width of 16 in (40 cm), so a group knits into one patch.
It grows 3½ ft (100 cm) tall. Give it the full distance from anything taller, or it will lean out towards the light.
How many cardinal flower plants do I need?
At 14 in apart, set out in staggered rows:
- 9 to fill 10 square feet (about 1 m²)
- 9 for a single row 10 ft (3 m) long
- 28 to fill a 4 × 8 ft bed on its own
In a mixed border, plant it as one at a time, repeated along the bed at intervals; a slender one reads better as a clump of three.
In the bed above, the planner used four in two groups.
Is cardinal flower poisonous to dogs and cats?
Yes: moderate toxicity to people, dogs, cats and horses. All parts are poisonous if eaten in quantity, causing vomiting, weakness and, in serious cases, convulsions.
Rated from NC State Extension and the ASPCA. Where references disagree, the more cautious rating is used.
Do deer eat cardinal flower?
They may. NC State does not list it as resistant to deer or rabbits. Where they visit, protect it, or plant it among ones they avoid.
What flowers after cardinal flower?
Cardinal flower is over by mid September. These start as it finishes and carry the same spot on, so it never goes flat:
- Garden chrysanthemum: from mid September to late October, 24 in tall, to stand in front of it and cover its fading stems.
- Blue-stemmed goldenrod: from early September to mid October, 2½ ft tall, to stand in front of it and cover its fading stems.
- Toad lily: from mid September to mid October, 2½ ft tall, to stand in front of it and cover its fading stems.
What does cardinal flower look like in winter?
Cardinal flower dies down to the ground and there is nothing to see until spring. The old stems can be cut in autumn, or left until spring as shelter for overwintering insects.
Is cardinal flower good for bees and butterflies?
Cardinal flower is visited by pollinators, butterflies and hummingbirds.
It is native to the United States and Canada.
More Lobelia
- Cardinal flower 'Queen Victoria' Lobelia cardinalis 'Queen Victoria'
- Great blue lobelia Lobelia siphilitica
- Purple lobelia Lobelia x speciosa 'Vedrariensis'
In these guides
- Plants for wet soil and rain gardens
- Garden plants toxic to cats
- Garden plants toxic to dogs
- Native perennials for pollinators
- Native plants for shade
- Garden plants native to Canada
- Plants for hummingbirds
- Plants for butterflies
- Plants with spires: vertical accents
Zone guides: Zone 3 · Zone 4 · Zone 5 · Zone 6 · Zone 7 · Zone 8 · Zone 9
Every fact on record
- Type
- Perennial
- Size
- 3½ ft (100 cm) tall, 16 in (40 cm) wide
- Plant
- 14 in (35 cm) apart
- Height class
- Moderately tall (3 to 4 ft)
- Place in the bed
- Back
- Flowers
- Late July to mid September; upright spires; red
- Leaves
- Medium texture, herbaceous; green
- Shape
- Upright, clumping
- Hardy in
- USDA zones 3 to 9
- Light
- Full sun, part sun, part shade
- Soil
- Rich, moist to wet
- Water
- High
- Feeding
- Moderate, in spring
- Family
- Campanulaceae
- Comes from
- Eastern United States
- Attracts
- Pollinators, butterflies, hummingbirds
- Stands up to
- Wet soil
Checked against NC State Extension, ASPCA poison lists and VASCAN (plants of Canada). Flowering times are for zone 5: later in colder zones, earlier in warmer ones. Toxicity and spread information is a general gardening guide, not veterinary or medical advice, and invasive status varies by region. If a person or pet eats a plant, contact poison control or a vet. Check your local invasive species list before planting anything with a spread warning.