Alnus glutinosa 'Imperialis'

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alder 'Imperialis'

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alder 'Imperialis' RHS 2002
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Trees
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A slow-growing medium-sized tree of conical outline and elegant habit, the leaves deeply pinnately lobed. Male catkins purplish, fruits small, cone-like

Position

Full sun

Soil Types

Chalk, Clay, Loam

Max Height

Higher than 12 metres

Max Spread

4-8 metres

Size

Time to Maturity
20–50 years
Max Spread
4-8 metres
Max Height
Higher than 12 metres

Growing Conditions

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

Position

Full sun
Aspect
West–facing or South–facing or North–facing or East–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
Betulaceae
Native to GB/Ireland
No
Foliage
Deciduous
Habit
Columnar upright
Genus
Alnus are vigorous deciduous trees and large shrubs with rounded leaves and often conspicuous catkins in winter
Name Status
Accepted

How to Grow

Cultivation

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

Propagation

Propagate by seed or hardwood cuttings

Suggested planting locations and garden types

  • Coastal
  • Wildflower meadow
  • Wildlife gardens
  • Low Maintenance

Pruning

Pruning group 1

Pests

May be susceptible to alder sucker and leaf-mining sawflies

Diseases

May be susceptible to Phytophthora and honey fungus