Alnus rubra

RHS Plant Profile
red alder

Save a plant

Where do you want to save Alnus rubra?

Plants I own
Wishlist
Go to My Plants
red alder RHS
red alder RHS
red alder RHS

Other common names

Californian red alder, Oregon alder, tag alder

Synonyms

Alnus oregana

Trees
Buy this from Plant Nurseries
6 Suppliers

A medium-sized tree, to around 19m, fast-growing with a graceful habit, producing a narrow pyramidal head with rather pendulous branches. Leaves large, lobed, dark green above, greyish beneath. Long male catkins to 15cm. Fruits barrel-shaped, to 1.5cm long

Position

Full sun

Soil Types

Chalk, Clay, Loam, Sand

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 Sand
Moisture
Moist but well–drained
pH
Acid or Alkaline or Neutral

Position

Full sun
Aspect
West–facing or South–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
Correct
Plant Range
Alaska to California

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 in a seedbed as soon as ripe. Root hardwood cuttings in winter and softwood cuttings in summer. Bud grafting can be performed in late summer

Suggested planting locations and garden types

  • Architectural
  • Wildlife gardens
  • Low Maintenance
  • Hedging and screens

Pruning

Requires minimal pruning

Pests

Generally pest-free

Diseases

May be susceptible to Phytophthora and honey fungus