Alnus cordata subsp. neapolitana

RHS Plant Profile

Neapolitan alder

Synonyms

Alnus cordata misapplied

Trees

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A fast-growing, deciduous tree to around 15m in height in the right conditions, with heart-shaped dark green leaves, glossy on the top, and horizontal growth on the side of the branches. Leaves remain green and on the tree well into autumn. Yellow catkins appear on both male and female trees in the spring, followed by clusters of pineapple-shaped greenish-brown fruits. Small, winged seeds are dispersed in winter. Makes a suitable windbreak and screen for large, open areas

Position

Full sun

Soil Types

Chalk, Clay, Loam

Size

Time to Maturity: 20–50 years

Growing Conditions

Chalk Clay Loam

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

Position

Full sun

Aspect: East–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): H6

Colour & Scent

Season	Stem	Flower	Foliage	Fruit
Spring
Summer
Autumn
Winter

Botanical Details

Family: Betulaceae
Native to GB/Ireland: No
Foliage: Deciduous
Habit: Spreading branched
Genus: Alnus are vigorous deciduous trees and large shrubs with rounded leaves and often conspicuous catkins in winter
Name Status: Correct
Plant Range: S Italy

How to Grow

Cultivation

Thrives in fertile, moist but well-drained soil, but tolerates a range of conditions including poor drainage. Can make a fast-growing screen on wet sites

Propagation

Propagate by seed or by hardwood cuttings

Suggested planting locations and garden types

Architectural
Low Maintenance
Hedging and screens

Pruning

Pruning group 1

Pests

May be susceptible to alder sucker, alder leaf beetle and leaf-mining sawflies

Diseases

May be susceptible to phytophthora root rots and honey fungus