Kniphofia caulescens 'Oxford Blue'

RHS Plant Profile
caulescent red-hot poker 'Oxford Blue'

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Herbaceous Perennial

An herbaceous perennial reaching approximately 60cm in height when in flower with blue, spiky, glaucous leaves and spikes of tubular, orange and yellow flowers that appear in summer to autumn

Position

Full sun

Soil Types

Loam, Sand

Max Height

1-1.5 metres

Max Spread

0.1-0.5 metres

Size

Time to Maturity
2–5 years
Max Spread
0.1-0.5 metres
Max Height
1-1.5 metres

Growing Conditions

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

Position

Full sun
Aspect
South–facing or West–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)
H5
Drought Resistance
Yes

Colour & Scent

Season Stem Flower Foliage Fruit
Spring
Summer
Autumn
Winter

Botanical Details

Family
Asphodelaceae
Native to GB/Ireland
No
Foliage
Evergreen
Habit
Clump forming, Columnar upright
Genus
Kniphofia may be evergreen or herbaceous perennials, with linear or strap-shaped leaves and erect stems bearing a dense raceme of tubular, usually pendent flowers
Name Status
Accepted

How to Grow

Cultivation

Grow in full sun and fertile, moist but well-drained soil that isn’t too wet over winter. See kniphofia cultivation for further advice

Propagation

Propagate by division of established clumps in late spring or by taking offshoots from the crown

Suggested planting locations and garden types

  • Architectural
  • City and courtyard gardens
  • Coastal
  • Cottage and informal garden
  • Gravel garden
  • Flower borders and beds

Pruning

Cut down old flower stems after flowering; old or dead leaves can be tidied up or removed in mid-spring

Pests

May be susceptible to aphids, thrips, slugs and snails

Diseases

Generally disease-free