Photo: Barnes, Dr. Thomas G., Public domain · source

Perennial · Campanulaceae

Cardinal flower

Lobelia cardinalis

In other languages: Rode lobelia (Nederlands) · Lobélie cardinale (Français)

The cardinal flower comes from North and Central America, where it grows along stream banks, in marshes and in wet woodland. It is an upright perennial about 90 cm tall, with a rosette of leaves at ground level and long, narrow leaves on the stems. From July to September it carries spikes of vivid scarlet, two-lipped flowers. Gardeners choose it for that intense colour, rare in late summer, and because it does well in wet soil or at the edge of a pond. It is often short-lived, but with a good spot and winter protection it will last a number of years.

Caution: All parts of the plant are poisonous if swallowed. Do not plant it where small children play, keep dogs and cats away from it and make sure grazing animals cannot reach it. Wash your hands after handling the plant.

Updated on 10 October 2026

Light
Sun or partial shade
preferably some sun
Moisture
Moist to wet
must not dry out
Legal basis
Loam, clay or peat
acid to neutral
Hardiness
down to -15 °C
protect young plants
Size
0.9 m
tall, 0.3 m wide
Flowering
July–September

Key facts
Pruning months	August and October
Height	0.9 m
Native to Belgium	No, planted
Good for bees, butterflies and birds	Yes, for bees
Poisonous to people and pets	Yes, take care with children and pets
Flowering	July–September

Identify

Cardinal flower: how do you recognise it?

Habit: A slender, upright plant about 90 cm tall and 30 cm wide, rising from a rosette of leaves.
Leaves: Lance-shaped and finely toothed, green, sometimes flushed reddish brown.
Flower: Two-lipped flowers 3–4 cm long in long, loose spikes, from July to September.
Colour: Vivid scarlet; there are also white and pink forms.
Roots: Shallow, fibrous roots; after flowering the plant forms new rosettes at the base.

Flowering: July–September · Plants: May–June · Pruning: August and October

In your garden

Why grow it?

One of the brightest red flowers in the garden, from July to September.
It thrives in wet soil and at pond edges, where many border plants rot.
Slender, straight spikes that stand out among grasses and low plants.
Bees and bumblebees visit the flowers.
It needs little space: slim enough for a small garden or a large pot.

Cardinal flower: where does it grow best?

Sun or partial shade; in sun the soil must always stay moist.
Humus-rich soil: loam, clay or peat, acid to neutral.
Wet soil that never dries out, for example at a pond edge or in a bog garden.
Allow 25–30 cm between plants and plant them in groups for the best effect.

Light: Sun and partial shade
Soil type: Loam, clay or peat
Acidity: Acid or neutral
Moisture: Wet
Size: 0.9 m tall, 0.3 m wide
Hardiness: Hardy (to -15 °C)

Goes well with

Purple loosestrife: A native plant with purple spikes, in the same wet spot and the same months.
Hemp agrimony: A native plant with dusky pink flower heads that draws butterflies at the water’s edge.
Japanese iris: Broad flowers in June–July; the cardinal flower then takes over.
Sedges: A green, grassy backdrop that makes the red glow.

Maintenance

Cardinal flower: when and how to plant it?

Plant in May–June.

Plant in May–June, once the night frosts are over, so it can root well before winter.
Dig a hole and mix in plenty of compost or leaf mould.
Set the plant at the same depth as in the pot: the rosette stays at soil level.
Keep 25–30 cm between plants.
Water generously straight away and keep the soil moist at all times afterwards.
Mulch with leaf mould to hold in moisture.

Care

Watering: The soil must never dry out. In dry spells, water every few days, even at a pond edge that dries out.
Feeding: A little compost or organic fertiliser in May; that is enough.
Support: In a windy spot, a small cane keeps the spikes upright.
Spent flowers: Cut the first spent spike back to just above a side shoot: the side branches will then flower for longer.
Winter protection: Cover the clump with leaves in winter: wet frost is its worst enemy.

Tip: Always keep the soil moist and cover the clump with leaves in winter. In autumn, pot up a few rosettes as a back-up: that way you will never lose it.

Cardinal flower: when to prune it?

Pruning months: August and October.

When: It is hardly pruned. In August, cut back spent spikes, and in October, after flowering, cut the stems down to just above the leaf rosettes.

How:

In August, cut spent spikes back to just above a side shoot for more flowers.
In October, cut the stems back to just above the rosettes at the base.
Do not damage the rosettes: the plant grows again from them next year.
Then cover the rosettes loosely with leaves.

Caution: Wear gloves and wash your hands afterwards: the plant is poisonous.

Pruning: when and how · Pruning calendar and basic rules

Propagation

Division: In April–May, separate the young rosettes at the base and replant each one on its own. This also keeps the plant young.
Cuttings: In July, insert 10 cm cuttings from non-flowering stems into moist cutting compost. They root quickly; keep them frost-free in their first winter.

Cardinal flower: how does it get through the winter?

Hardy to −15 °C: protect young plants.

Hardy to about −15 °C, but wet frost is its worst enemy.
Cover the clump in winter with a loose layer of leaves or straw and remove it again in March–April.
As a back-up, pot up a few rosettes in autumn and overwinter them cool and frost-free, for example in a cold frame.
In a pot: keep it cool and frost-free in winter and the compost slightly moist.

Diseases and pests

Winter rot: The rosette rots in wet frost. Cover with leaves and overwinter a few rosettes in a pot as a back-up.
Slugs: They eat the young rosettes in spring. Pick them off or set a beer trap.
Drying out: Brown leaves and few flowers when the soil dries out. Always keep it moist and mulch.
Short life: A plant often lives only a few years. Divide it every 2–3 years or take cuttings to renew it.

Through the year

March: In mild weather, partly remove the winter cover.
April: Remove the winter cover. Divide rosettes. Watch for slugs.
May: Plant after the last frost. Add compost.
June: Plant. Keep the soil moist.
July: Flowering begins. Take cuttings. Water.
August: Full flower. Cut spent spikes back to just above a side shoot.
September: Last flowers. Keep the soil moist.
October: Cut stems back to just above the rosettes. Pot up back-up rosettes.
November: Cover the clump with leaves or straw.
December: Check the winter cover.

Use

Edible and useful

Not edible. All parts of lobelia are poisonous: they contain lobeline and related alkaloids, which act like nicotine. Swallowing any causes nausea, vomiting, drooling and stomach ache, and in larger amounts dizziness, sweating, a fast heartbeat and breathing problems. A related species was once used as a herb for asthma and to stop smoking: never make teas or preparations from your garden lobelia. Keep children, dogs, cats and grazing animals away from the plant, and wear gloves when cutting back, as the milky sap can irritate the skin. If any is swallowed, call a poison centre (in Belgium 070 245 245) or your doctor at once.

Good for wildlife

Bees: Nectar and pollen for honeybees and wild bees.

You and this species

Did you know?

The name cardinalis refers to the scarlet red of cardinals’ robes.
In North America it is pollinated mainly by hummingbirds, which reach the nectar with their long bills.
The genus Lobelia is named after Matthias de l’Obel, a 16th-century Flemish botanist born in Lille.

Garden plants · All species