Indigenous Trees – Black Alder

Silence River, originally uploaded to flickr by Matthias17

From British Trees

Where found

Very tolerant of water logged conditions whilst dormant. Typical streamside tree and as a specific habitat – Alder Carr – in Lake District and Norfolk Broads. All soil types except poor acid peats. Fixes nitrogen via root nodules and will grow on relatively infertile soils and hence used for site reclamation. Natural throughout British Isles and most of Europe.

image of an Alder leaf. WTPL/Peter Paice

Phenology timeline

Flowers Leaves Fruit Ripen Fall
Feb-Mar Apr Oct-Dec Dec Nov

Propagation and growth
Grown from seed. The seed does not undergo dormancy by germination rate increased if given a period of moist chilling at 0.5C for up to 10 weeks. The seeds float and are carried by streams naturally germinating in mud. Seeds are red brown flakes – 250,000 seeds per Kg. Often rapid growth in first year but best kept in nursery and planted out in second year. Can be beneficially grown with oak on damp sites and ash.

From the Royal Forestry Society website –

Most alders are pioneer species. They invade and thrive in gaps and clearings in forests, often on the poorest soils. Many tolerate a high water-table and periodic flooding.

Alder shows all the features of a successful pioneer survival strategy – it produces numerous small seeds, rapidly colonises bare open ground, has fast initial growth and a short life-span. They need good light, open ground and cannot tolerate shade and competition – in natural conditions they are overtaken by larger trees which out-shade them.

Five species of alder are commonly found in the UK – one native and four imported.

In British forestry, they are of little value as timber trees but can be used as “nurses” to protect and bring on more valuable trees or as soil improvers on sites with undeveloped soils like reclamation sites. Most alders coppice well.

Alnus glutinosa leaves, male amd female catkins, from Bilder ur Nordens Flora
Alnus glutinosa leaves, male amd female catkins, from Bilder ur Nordens Flora

The black alder – Alnus glutinosa – is native throughout the British Isles and much of Continental Europe. It is found widely but particularly on wetter soils, often at high elevations on infertile terrains although it does not thrive on acid-peat or dry-sandy substrates. It can form small woods or “carrs” on boggy land.

The grey alder – Alnus incana – is found across central Europe. Introduced to Britain in 1780, it resembles the native Black Alder in its lifestyle and site requirements.

Italian alder – Alnus cordata – from southern Italy and Corsica, was brought to Britain in 1820. Like all alders, it is a strong light demander and withstands exposure and pollution well, copes better with drier, calcareous soils than its relatives and is a good landscape tree.

Grey and Italian alders have been planted as windbreaks round orchards.

The red or Oregon alder – Alnus rubra – is native to large tracts of the Pacific Coast of north America, where it is closely associated with Sitka spruce. First introduced into Britain in the late 1800s, it has been tried as a timber tree with mixed results although it is a significant pulp wood in its native home.

The green alder – Alnus viridis – has a shrubby growth form and lives in arctic and alpine regions of Europe. It provides vital stability and fertility when planted to start reclaiming bare derelict land like China Clay spoil in Cornwall.

Over the last few years, many riverside alders in Britain have succumbed to a fungus from the Phytophthora group.

Similar to poplar, alder wood is one of the weakest hardwoods. However it is resistant to decay under water so was sometimes used for sluice gates and also for charcoal in making gunpowder.

Alder and larch planted to start reclaiming a vast opencast coal site in S.Wales
Catkins of the common alder in February

Alders have catkins – the male and female ones open in early spring, before the leaves appear, so the wind can carry pollen from male to female flowers.

Each long, dangling male catkin is a complex structure loaded with about 120 individual flowers and 480 pollen-producing stamens. After the clouds of yellow pollen are shed, the male catkins wither and fall.

The plump, club-shaped female catkins have tufts of hair or stigma to trap the pollen drifting in the air.

False cones on alder
False cones on alder
© J. Jackson

After pollination, female alder catkins ripen into a woody “false-cone”. In autumn, the scales open and release the seeds to be dispersed both wind and water in this riverside plant. The empty “false-cones” hang on the twigs for several years, and make alder easy to recognise.

Now cleared and drained for intensive agriculture, much fenland was originally dominated by alder carrs.

Further reading : Gibbs, J. N. & Lonsdale, D. (1998). Phytophthora disease of alder. Forestry Commission Information Note 6, 5pp.

From wikipedia

Black Alder, European Alder, Irish Fearnog or Common Alder (Alnus glutinosa) is an alder tree native to most of Europe, including all of Britain, Fennoscandia and locally in southwest Asia.

Alnus glutinosa.jpg
Alnus glutinosa foliage and fruit

The Black Alder thrives best in moist soils, and grows under favourable circumstances to a height of 20-30 m, though often less. It is characterized by its 5–10 cm short-stalked rounded leaves 6–12 cm long, becoming wedge-shaped at the base and with a slightly toothed margin. When young they are somewhat glutinous, whence the specific name, becoming later a glossy dark green. As with some other plants growing near water it keeps its leaves longer than do trees in drier situations, the glossy green foliage lasting after other trees have put on the red or brown of autumn, which renders it valuable for landscape effect. As the Latin name glutinosa implies, the buds and young leaves are slightly sticky with a resinous gum.



12  year old European Black Alder

12 year old European Black Alder

The monoecious flowers are wind-pollinated catkins: the slender cylindrical male catkins are pendulous, reddish in colour and 5–10 cm long; the female are smaller, 2 cm in length and dark brown to black in colour, hard, somewhat woody, and superficially similar to some conifer cones. When the small winged seeds have been scattered the ripe, woody, blackish cones remain, often lasting through the winter. The alder is readily propagated by seeds, but throws up root suckers abundantly.


Recently coppiced stumps, showing the orange-red wood
Recently coppiced stumps, showing the orange-red wood

It is important as coppice-wood on marshy ground. The wood is soft, white when first cut and turning to pale red; the knots are beautifully mottled. Under water the wood is very durable, and it is therefore used for piles. The supports of the Rialto at Venice, and many buildings at Amsterdam, are of Alder-wood. It is also the traditional wood burnt to produce smoked fish and other smoked foods, though in some areas other woods are more often used now. Furniture is sometimes made from the wood, and it supplies excellent charcoal for gunpowder. The bark is astringent; it is used for tanning and dyeing.

Female inflorescence
Female inflorescence

Cultural aspects

Frequently, such as in Brythonic and Norse mythology, the Alder is a symbol of resurrection, possibly because the wood turns from white to reddish-purple when cut, similar to human blood. The first humans in Norse mythology were made from Ash and Alder trees. In Ireland, reverence for the Alder tree was so great that cutting one down was a criminal offence. In other places, such as Newfoundland, the Alder’s medicinal effects were prized; it has been used to treat burns, rheumatism and itching.

From Trees Mystical World Wide Web

In the Tyrol belief had it that the Alder tree was often used by sorcerers. One particular legend tells of how a small boy who climbed up a large tree, He looked down and saw a number of sorcerers at the foot of the tree. Whilst watching they cut up a dead woman’s body and proceeded to throw the pieces high into the air, so high in fact that the boy caught one of the pieces. The pieces fell back down and the sorcerers began to count them but one was missing. Realising this they replaced the piece with wood from the Alder tree, and the woman came back to life. Ever since the tree has been associated with the dead, and their resurrection back to life.

R. Rapin’s poem tells of the origin of the Alder (and Willow);

‘De Hortorum Cultura’
‘Of watery race Alders and Willows spread
O’er silver brooks their melancholy shade,
Which heretofore (thus tales have been believed)
Were two poor men, who by their fishing lived;
Till on a day when Pales’ feast was held,
And all the town with pious mirth was filled,
This impious pair alone her rites despised,
Pursued their care, till she their crime chastised:
While from the banks they gazed upon the flood,
The angry goddess fixed them where they stood,
Transformed to sets, and just examples made
To such as slight devotion for their trade.
At length, well watered by the bounteous stream
They gained a root, and spreading trees became;
Yet pale their leaves, as conscious how they fell,
Which croaking frogs with vile reproaches tell.’

Diviners in search of water hidden underground are known to often use forked branches taken from the Alder tree traditionally called ‘Wishing Rods’ (also Apple, Hazel and Beech).


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