Photo: Didier Descouens, CC BY-SA 4.0 · source

Perennial · Campanulaceae

Hybrid cardinal flower

Lobelia × speciosa

In other languages: Lobelia (Nederlands) · Lobélie hybride (Français)

Lobelia × speciosa is the collective name for garden hybrids that arose from North American and Mexican species, such as the cardinal flower (Lobelia cardinalis) and the great blue lobelia (Lobelia siphilitica). They are upright perennials of about 80 cm with sturdy flower stems covered in two-lipped tubular flowers in intense red, pink or purple, from July to September. Many cultivars also have bronze to dark purple foliage. The plants like moist, humus-rich soil and look good in a damp border or beside a pond. They are less hardy than the blue lobelia and are often short-lived. All parts are poisonous.

Caution: Poisonous: all parts contain alkaloids and the milky sap can irritate the skin. Children, cats, dogs and grazing animals must not eat it; wear gloves when pruning.

Updated on 10 October 2026

Light
Sun or partial shade
preferably some sun
Moisture
Normal to wet
must not dry out
Legal basis
Loam, clay or peat
acid to neutral
Hardiness
Fully hardy
down to -20 °C
Size
0.8 m
tall, 0.3 m wide
Flowering
July–September

Key facts
Pruning months	March
Height	0.8 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

Hybrid cardinal flower: how do you recognise it?

Habit: Upright, clump-forming perennial about 80 cm tall and 30 cm wide, with sturdy, unbranched flower stems.
Leaves: Lance-shaped, 10–15 cm long, green to bronze-red or dark purple (depending on the cultivar); a rosette at the base, leaves scattered along the stem.
Flower: Two-lipped tubular flowers of about 3–4 cm in long, dense spikes, red, pink or purple, from July to September.
Sap: Milky sap in stems and leaves, which is poisonous and can irritate the skin.
Roots: Shallow, fibrous root system that needs plenty of moisture; forms new root rosettes in autumn.

Flowering: July–September · Plants: May–June · Pruning: March

In your garden

Why grow it?

Bright flower towers in red, pink or purple from July to September, when many borders begin to tire.
Many cultivars have bronze or purple foliage that looks good even without flowers.
Fits wet spots where many other perennials fail, such as a pond edge or stream bank.
The tubular flowers are visited by bees and bumblebees.
A good vertical accent in a border with large-leaved plants or grasses.

Hybrid cardinal flower: where does it grow best?

Sun to part shade; in sun it needs more water, in part shade the flower colour stays fresher.
Humus-rich loam, clay or peaty soil that stays moist, acid to neutral; slightly acid soil is ideal.
Normal to wet: the soil must never dry out, but standing water in winter can rot the rosette.
A sheltered spot, because the tall stems blow over easily; suits a pond edge, damp border or stream bank.
Allow 30–40 cm between plants.

Light: Sun and partial shade
Soil type: Loam, clay or peat
Acidity: Acid or neutral
Moisture: Normal or wet
Size: 0.8 m tall, 0.3 m wide
Hardiness: Hardy (to -20 °C)

Goes well with

Daylily: A similar damp spot; orange or yellow contrasts with red.
Meadowsweet: Frothy white or pink plumes that go well with the upright spikes.
Yellow flag iris: Suits the pond edge and flowers earlier in the season.
Astilbe: Pink and red plumes in the same damp part shade.
Purple moor grass: Fine grass that frames the bright flower towers lightly.

Maintenance

Hybrid cardinal flower: when and how to plant it?

Plant in May–June.

Plant in May or June, when night frosts are no longer expected.
Loosen the soil and mix in a generous amount of compost or leaf mould.
Dig a hole as deep as the pot and twice as wide.
Set the plant at the same depth as in its pot, with the rosette at soil level; space 30–40 cm apart.
Water well straight away and keep the soil constantly moist for the first weeks.
Spread a 5 cm layer of leaf mould or bark around the base, without covering the rosette.

Care

Watering: Keep constantly moist, also during dry spells and in the first summer. At a pond or stream edge this usually happens by itself.
Feeding: Compost or an organic fertiliser in spring. Not too much nitrogen, or the stems become floppy.
Mulching: A layer of leaf mould in spring keeps the soil cool and moist; a thicker layer in late autumn acts as winter cover.
Spent flowers: Cut faded spikes back to just above a side shoot; the plant then flowers for longer.
Support: In an open spot, tie the tall stems in or let them grow through other plants.

Tip: Cultivars in red, pink and purple for a damp border or pond edge. Never let the soil dry out and cover the clump in hard winters.

Hybrid cardinal flower: when to prune it?

Pruning months: March.

When: In March cut away the old stems. During flowering cut off the faded spikes.

How:

In March, cut all old, dead stems down to just above the ground, without damaging the new rosettes.
During flowering, cut faded spikes back to just above a side shoot.
Leave the leaf rosettes in autumn and winter: they protect the plant.

Caution: Wear gloves: the milky sap is poisonous and can irritate the skin.

Pruning: when and how · Pruning calendar and basic rules

Propagation

Division: Every two to three years in April: lift the clump, divide it into pieces with a rosette and roots and replant straight away. This keeps the plant strong and young.
Cuttings: In spring, basal cuttings from young shoots or rosettes, in moist sandy compost in a bright spot.

Hybrid cardinal flower: how does it get through the winter?

Hardy to −20 °C.

Hardy to about −20 °C, but often less reliable in lasting wet: the rosettes can rot away in wet winters.
Cover the clump in November with a thick layer of leaf mould, dry leaves or bracken, especially in hard winters.
Keep a spare: take a few cuttings in spring or keep a division in a cold frame.

Diseases and pests

Slugs: Young rosettes and shoots are eaten in spring. Collect them in the evening and protect young plants.
Drying out: Limp leaves and brown edges in dry weather. Water and mulch.
Winter rot: The rosette goes soft and brown in wet soil. Provide drainage and cover with dry leaves.
Aphids: Sometimes on young shoots. A jet of water is usually enough.

Through the year

March: Cut back old stems. Apply compost.
April: Divide clumps. Watch for slugs.
May: Plant. Mulch.
June: Plant. Water in dry weather.
July: Flowering begins. Keep constantly moist.
August: Flowering. Cut off faded spikes.
September: Last flowers.
November: Cover with a layer of leaves or compost.

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 genus Lobelia is named after Matthias de l’Obel (1538–1616), a Flemish physician and botanist from Lille.
The cardinal flower (Lobelia cardinalis), one of the parents, owes its English name to the red robes of Catholic cardinals.
Garden hybrids like this one arose from crosses between, among others, the red and the blue lobelia.

Garden plants · All species