Trachelium caeruleum

RHS Plant Profile
blue throatwort

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blue throatwort RHS 1987

Other common names

throatwort

Bedding Conservatory Greenhouse Herbaceous Perennial Annual Biennial

An erect perennial to 90cm, usually grown as an annual, with lance-shaped leaves and small, slightly fragrant, violet-blue flowers in domed clusters to 15cm across in summer

Position

Full sun

Soil Types

Loam, Sand

Max Height

0.5-1 metres

Max Spread

0.1-0.5 metres

Size

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

Growing Conditions

Loam Sand
Moisture
Moist but well–drained
pH
Acid or Alkaline or Neutral

Position

Full sun
Aspect
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)
H2

Colour & Scent

Fragrance Flower
Season Stem Flower Foliage Fruit
Spring
Summer
Autumn
Winter

Botanical Details

Family
Campanulaceae
Native to GB/Ireland
No
Foliage
Deciduous
Habit
Bushy
Genus
Trachelium can be cushion-forming or erect perennials with small, simple leaves and tubular flowers with 5 spreading lobes, in summer
Name Status
Correct
Plant Range
W Mediterranean

How to Grow

Cultivation

Grow in moderately fertile, well-drained soil in full sun, ideally with some midday sun. Water freely in dry weather

Propagation

Propagate by seed sown at 16°C in spring

Suggested planting locations and garden types

  • City and courtyard gardens
  • Patio and container plants
  • Cottage and informal garden
  • Flower borders and beds
  • Cut flowers
  • Wall side borders

Pruning

Cut back after flowering

Pests

Generally pest-free

Diseases

Generally disease-free