Lobelia cardinalis

RHS Plant Profile
cardinal flower

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Other common names

bog sage, hog's physic, Indian pink, red bay, scarlet lobelia, slinkweed, water gladiole, brilliant lobelia

Synonyms

Lobelia cardinalis scarlet
Lobelia splendens
Lobelia fulgens

Bogs Herbaceous Perennial
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An erect, clump-forming herbaceous perennial to 90cm in height, with rather glossy bright green oblong leaves and brilliant scarlet, two-lipped flowers 5cm in length in terminal spikes

Position

Full sun, Partial shade

Soil Types

Loam

Max Height

0.5-1 metres

Max Spread

0.1-0.5 metres

Size

Time to Maturity
2–5 years
Max Spread
0.1-0.5 metres
Max Height
0.5-1 metres

Growing Conditions

Loam
Moisture
Poorly–drained
pH
Acid or Alkaline or Neutral

Position

Full sun Partial shade
Aspect
South–facing or West–facing or East–facing
Exposure
Exposed or Sheltered
Hardiness

Hardiness Ratings

All ratings refer to the UK growing conditions unless otherwise stated. Minimum temperature ranges (in degrees C) are shown in brackets

  • H1A: under glass all year (>15C)
  • H1B: can be grown outside in the summer (10 - 15)
  • H1C: can be grown outside in the summer (5 - 10)
  • H2: tolerant of low temperatures, but not surviving being frozen (1 to 5)
  • H3: hardy in coastal and relatively mild parts of the UK (-5 to 1)
  • H4: hardy through most of the UK (-10 to -5)
  • H5: hardy in most places throughout the UK even in severe winters (-15 to -10)
  • H6: hardy in all of UK and northern Europe (-20 to -15)
  • H7: hardy in the severest European continental climates (< -20)
H3

Colour & Scent

Season Stem Flower Foliage Fruit
Spring
Summer
Autumn
Winter

Botanical Details

Family
Campanulaceae
Native to GB/Ireland
No
Foliage
Deciduous
Habit
Clump forming
Potentially harmful
Harmful if eatenskin irritant. Wear gloves and other protective equipment when handling Wear gloves and other protective equipment when handling. Pets: Harmful if eatenskin irritant. For further information and contact numbers regarding pets, see the HTA guide to potentially harmful plants
Genus
Lobelia can be annuals, perennials or shrubs, with simple leaves and showy 2-lipped flowers that may be solitary or in racemes or panicles
Name Status
Correct
Plant Range
N America

How to Grow

Cultivation

Grow in deep, fertile, reliably moist soil in full sun or partial shade

Propagation

Propagate by seed sown in gentle heat as soon as ripe, or by bud cuttings in late summer

Suggested planting locations and garden types

  • Cottage and informal garden
  • Flower borders and beds

Pruning

Cut back after flowering

Pests

May be susceptible to slugs

Diseases

May be susceptible to crown rot