Sempervivum 'Black Knight'

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houseleek 'Black Knight'

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Cactus Succulent
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A mat-forming, evergreen succulent producing rosettes of fleshy, oval to strap-shaped, darkest burgundy leaves with green bases, the leaves almost black during summer. Tall spikes of starry pink flowers produced from mature rosettes, die off after flowering in summer and are replaced by new offsets

Position

Full sun

Soil Types

Chalk, Loam, Sand

Max Height

Up to 10 cm

Max Spread

0.1-0.5 metres

Size

Time to Maturity
2–5 years
Max Spread
0.1-0.5 metres
Max Height
Up to 10 cm

Growing Conditions

Chalk Loam Sand
Moisture
Well–drained
pH
Acid or Alkaline or Neutral

Position

Full sun
Aspect
East–facing or 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)
H7

Colour & Scent

Season Stem Flower Foliage Fruit
Spring
Summer
Autumn
Winter

Botanical Details

Family
Crassulaceae
Native to GB/Ireland
No
Foliage
Evergreen
Habit
Matforming
Genus
Sempervivum are evergreen perennials forming mats of fleshy-leaved rosettes, often attractively coloured, with star-shaped pink or pale yellow flowers in summer
Name Status
Accepted

How to Grow

Cultivation

Grow in moderately fertile sharply-drained soil with added grit, in full sun. Protect from excessive winter wet. Suitable for rock garden, scree bed, wall crevice, trough or alpine house. See sempervivum cultivation for further advice

Propagation

Propagate by seed sown in spring, or root offsets in spring

Suggested planting locations and garden types

  • City and courtyard gardens
  • Coastal
  • Cottage and informal garden
  • Gravel garden
  • Patio and container plants
  • Rock garden
  • Low Maintenance
  • Flower borders and beds
  • Garden edging
  • Ground cover

Pruning

No pruning required

Pests

May be susceptible to sempervivum leaf miner and vine weevil

Diseases

May be susceptible to a rust