Ilex aquifolium 'Crispa' (m)

RHS Plant Profile
screw holly

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screw holly RHS / Joanna Kossak

Synonyms

Ilex aquifolium 'Tortuosa'

Plants for pollinators
Trees

Small, slow-growing evergreen tree about 3m tall, with purple-grey bark, and thick leathery leaves that are twisted and curled, each with sharp, decurved spine. A male holly that is a good pollinator for female cultivars

Position

Full sun, Partial shade

Soil Types

Chalk, Clay, Loam, Sand

Max Height

2.5-4 metres

Max Spread

1.5-2.5 metres

Size

Time to Maturity
20–50 years
Max Spread
1.5-2.5 metres
Max Height
2.5-4 metres

Growing Conditions

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

Position

Full sun Partial shade
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)
H6

Colour & Scent

Season Stem Flower Foliage Fruit
Spring
Summer
Autumn
Winter

Botanical Details

Family
Aquifoliaceae
Native to GB/Ireland
No
Foliage
Evergreen
Habit
Columnar upright, Bushy
Potentially harmful
Fruit are ornamental - not to be eaten. Wear gloves and other protective equipment when handling. Pets: Fruit are ornamental - not to be eaten - see the HTA guide to potentially harmful plants for further information and useful contact numbers
Genus
Ilex can be deciduous or evergreen shrubs and trees with often spiny leaves, small white flowers (male and female usually on separate plants) and, on female plants, showy berries in autumn
Name Status
Accepted

How to Grow

Cultivation

Grow in moist but well-drained soil in full sun or part shade

Propagation

Propagate by semi-ripe cuttings in late summer or early autumn or propagate by hardwood cuttings in January with bottom heat

Suggested planting locations and garden types

  • Coastal
  • Cottage and informal garden
  • Wildlife gardens
  • Architectural
  • Low Maintenance
  • Hedging and screens

Pruning

Pruning group 1; trim hedges in early spring

Pests

May be susceptible to scale insects, holly leaf miner and young shoots may be susceptible to aphids

Diseases

May be susceptible to holly leaf blight, Phytophthora root rot and sometimes honey fungus