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Shrubs

Hydrangea macrophylla Black Steel Blue ('Klazu'PBR) (Black Steel Series) (H)

hydrangea [Black Steel Blue]

A deciduous shrub to 1.2m high with broadly oval, toothed mid green leaves and striking near-black stems. Dome-shaped clusters of pale blue flowers are produced from lime green buds in summer. Colours may vary depending on the pH of the soil; blue flower colour is best maintained in acidic soils

Synonyms
Hydrangea macrophylla 'Klazu'PBR
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Size
Ultimate height
1–1.5 metres
Time to ultimate height
2–5 years
Ultimate spread
0.1–0.5 metres
Growing conditions
Clay
Loam
Moisture
Moist but well–drained
pH
Acid, Neutral
Colour & scent
StemFlowerFoliageFruit
Spring Green
Summer Blue Purple Green
Autumn Green
Winter
Position
  • Full sun
  • Partial shade
Aspect

East–facing or South–facing or West–facing

Exposure
Exposed or Sheltered
Hardiness
H5
Botanical details
Family
Hydrangeaceae
Native to GB / Ireland
No
Foliage
Deciduous
Habit
Bushy
Potentially harmful
Skin allergen. Wear gloves and other protective equipment when handling. Pets (dogs, cats): Harmful if eaten. For further information and contact numbers regarding pets, see the HTA guide to potentially harmful plants
Genus

Hydrangea can be deciduous or evergreen shrubs, or self-clinging climbers, with flowers in clusters usually comprising both small fertile and more showy sterile flowers; often good autumn colour

Name status

Trade

Horticultural Group
Hortensia hydrangeas (also known as mopheads) are compact bushy deciduous shrubs with broadly ovate leaves and rounded flower clusters composed almost entirely of showy sterile flowers

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How to grow

Cultivation

Grow in any moist but well-drained soil in partial shade or grow in sun if soil remains reliably moist. Improve chalky soils with organic matter to support good growth. See shrubby hydrangea cultivation for further advice

Propagation

Propagate by softwood cuttings in early summer, or hardwood cuttings in winter. As this plant is protected by Plant Breeders' Rights, any propagation should be for personal rather than commercial use

Suggested planting locations and garden types
  • City and courtyard gardens
  • Cottage and informal garden
  • Coastal
  • Flower borders and beds
  • Wall side borders
Pruning

See pruning group 4 for further advice and video guide

Pests

May be susceptible to aphids, scale insects, vine weevil and capsid bug

Diseases

May be susceptible to a leaf spot, powdery mildews, grey moulds (Botrytis) and honey fungus (rarely)

Get involved

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