Italian alder

Profile

Family

Betulaceae

Habit

Tree

Height

25 m

Spread

8 m

Growth

very fast

Lifespan

100 years

First yield

after 6 years

Hardiness

zone 6–9

Shade tolerance

partial shade

Soil

Silt, Loam, Clay

Soil moisture

dry – near water

pH

5.6 – 7.6

Synonyms

A. cordifolia.

Uses

Other uses: As an excellent windbreak in coastal regions, the alder grows quite quickly and establishes itself well even on very windy sites. Five-year-old trees grown from seed have reached a height of four metres at an exposed site in Cornwall and show no signs of wind deformation. The alder is excellent as a pioneer tree species for reforesting wasteland, difficult sites etc. Through its rapid growth it quickly creates sheltered conditions in which other, more permanent tree species can later become established. Bacteria on the roots also fix nitrogen from the air. This not only enables the alder to grow well on nutrient-poor soils, but also makes nitrogen available to other plants nearby. Alders also have a dense leafy crown, the leaf fall of which contributes to humus formation in the soil in autumn. Alder seedlings cannot compete well in shade and therefore gradually die out as other tree species become established.

Growing

Thrives on poor and rather dry soils, even on chalk, but prefers proximity to water. Prefers heavy soils and moist sites. Grows well on heavy clay soils. Tolerates very infertile sites. This species lives in symbiosis with certain soil micro-organisms. These form nodules on the roots of the plants and fix atmospheric nitrogen. Some of this nitrogen is used by the growing plant, some is available to neighbouring plants. This highly decorative tree grows very quickly and reaches a height of 12 metres within 20 years at an exposed coastal site in Rosewarne, North Cornwall. It is very tolerant of salt-laden winds and establishes itself quickly at exposed sites. According to "World Economic Plants", the correct author of this species is (Loisel.) Loisel and not Desf., as we have given here. However, since all our other sources cite Desf., we have decided not to change this at the present time (1999).

Propagation

Seed – best sown in a cold frame as soon as ripe, and only lightly covered with soil. Seed sown in spring also germinates well as long as it is not covered. Germination takes place in spring as temperatures rise. Once the seedlings are large enough, prick them out into individual pots. If they have grown sufficiently, they can be planted out into their final position in summer. Otherwise they remain in pots outdoors and are planted out in spring. If you have enough seed, you can sow it thinly in a seedbed outdoors in spring. The seedlings can either be planted out into their final position in autumn/winter, or grown on in the seedbed for another season. Cuttings of mature wood, taken outdoors in autumn after leaf fall and inserted in sandy soil, are also suitable for propagation.

Origin & habitat

Europe - S. Italy, Corsica.

Naturally occurs in mountainous areas with a Mediterranean climate, mainly along riverbanks and moist slopes. Prefers deep, moderately dry to moist soils with neutral to slightly acidic pH. Found in open deciduous forests and forest edges, often at elevations up to about 1000 meters.

Related plants