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Alnus glutinosa 'Imperialis' AGM

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© RHS 2002

Characteristics

Plant type

Tree

Habit

Columnar/Upright

Resilience

Hardiness

H6 (hardy - very cold winter)

Colour

Flower

Pale Purple in Winter

Foliage

Green in Autumn, Spring and Summer

Fruit

Brown in Summer

Size

Ultimate height

Higher than 12 metres

Ultimate spread

4-8 metres

Time to ultimate height

20-50 years


Preferred common name

alder 'Imperialis'

Family

Betulaceae


Alnus are vigorous deciduous trees and large shrubs with rounded leaves and often conspicuous catkins in winter

'Imperialis' is a slow-growing medium-sized tree of conical outline and elegant habit, the leaves deeply pinnately lobed. Male catkins purplish, fruits small, cone-like

How to grow

Sunlight

  • Full sun

Aspect

  • North-facing, East-facing, South-facing or West-facing
  • Sheltered or Exposed

Cultivation

This genus is noted for its ability to thrive in poor, wet conditions and is widely used in land reclamation

Soil

  • Moist but well-drained or Poorly-drained
  • Acid, Alkaline or Neutral
  • Loam, Chalk or Clay

Propagation

Propagate by seed or hardwood cuttings

Suggested planting locations and garden types

Low Maintenance


How to care

Pruning

Pruning group 1

Pests

Can get alder sucker and leaf-mining sawflies

Diseases

Susceptible to Phytophthora