Alnus serrulata

RHS Plant Profile

smooth alder

Other common names

hazel alder

Shrubs

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A multi-stemmed deciduous shrub which can form a thicket. It has leathery green leaves which have no autumn colour and fall green in the autumn, and deep red, upright catkins which give it a red glow in winter. The tiny female flowers develop into clusters of long-lasting wooden cones

Position

Full sun, Partial shade

Soil Types

Chalk, Clay, Loam, Sand

Max Height

4-8 metres

Max Spread

4-8 metres

Size

Time to Maturity: 5–10 years
Max Spread: 4-8 metres
Max Height: 4-8 metres

Growing Conditions

Chalk Clay Loam Sand

Moisture: Moist but well–drained or Poorly–drained
pH: Acid or Alkaline or Neutral

Position

Full sun Partial shade

Aspect: East–facing or North–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): H5
Drought Resistance: Yes

Colour & Scent

Season	Stem	Flower	Foliage	Fruit
Spring
Summer
Autumn
Winter

Botanical Details

Family: Betulaceae
Native to GB/Ireland: No
Foliage: Deciduous
Habit: Bushy, Suckering
Genus: Alnus are vigorous deciduous trees and large shrubs with rounded leaves and often conspicuous catkins in winter
Name Status: Correct

How to Grow

Cultivation

Needs good light, permanently damp soil but very little fertility as they have nitrogen-fixing nodules on their roots. They are used for river bank stabilisation and other land reclamation purposes. This is seen to be much more tolerant of drought than other alder species

Propagation

Grow from seed or hardwood cuttings

Suggested planting locations and garden types

Wildlife gardens
Banks and slopes
Hedging and screens

Pruning

Pruning group 1

Pests

May be susceptible to alder sucker and leaf-mining sawflies

Diseases

May be susceptible to Phytophthora and honey fungus