Alnus glutinosa

Botanical Name : Alnus glutinosa
Family: Betulaceae
Genus: Alnus
Subgenus: Alnus
Species: A. glutinosa
Kingdom: Plantae
Order: Fagales

Synonyms: A. rotundifolia. Betula glutinosa.

Common Names: Alder, European alder , Common Alder, Black Alder

Habitat :Alnus glutinosa is native to most of Europe, including Britain, to Siberia, W. Asia and N. Africa. It grows on wet ground in woods, near lakes and along the sides of streams, often formng pure woods n succession to marsh or fen.
Description:
Alnus glutinosa is a medium size, short-lived deciduous Tree .It is a tree that thrives in moist soils, and grows under favourable circumstances to a height of 20 to 30 metres (66 to 98 ft) and exceptionally up to 37 metres (121 ft). Young trees have an upright habit of growth with a main axial stem but older trees develop an arched crown with crooked branches. The base of the trunk produces adventitious roots which grow down to the soil and may appear to be propping the trunk up. The bark of young trees is smooth, glossy and greenish-brown while in older trees it is dark grey and fissured. The branches are smooth and somewhat sticky, being scattered with resinous warts. The buds are purplish-brown and have short stalks. Both male and female catkins form in the autumn and remain dormant during the winter.

The leaves of the common alder are short-stalked, rounded, up to 10 cm (4 in) long with a slightly wedge-shaped base and a wavy, serrated margin. They have a glossy dark green upper surface and paler green underside with rusty-brown hairs in the angles of the veins. As with some other trees growing near water, the common alder keeps its leaves longer than do trees in drier situations, and the leaves remain green late into the autumn. As the Latin name glutinosa implies, the buds and young leaves are sticky with a resinous gum.

The species is monoecious and the flowers are wind-pollinated; the slender cylindrical male catkins are pendulous, reddish in colour and 5 to 10 cm (2 to 4 in) long; the female flowers are upright, broad and green, with short stalks. During the autumn they become dark brown to black in colour, hard, somewhat woody, and superficially similar to small conifer cones. They last through the winter and the small winged seeds are mostly scattered the following spring. The seeds are flattened reddish-brown nuts edged with webbing filled with pockets of air. This enables them to float for about a month which allows the seed to disperse widely.

Unlike some other species of tree, common alders do not produce shade leaves. The respiration rate of shaded foliage is the same as well-lit leaves but the rate of assimilation is lower. This means that as a tree in woodland grows taller, the lower branches die and soon decay, leaving a small crown and unbranched trunk.

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It has short-stalked rounded leaves and separate male and female flower in the form of catkins. The small, rounded fruits are cone-like and the seeds are dispersed by wind and water.

It is in leaf 11-Mar It is in flower from Mar to April, and the seeds ripen from Sep to November. The flowers are monoecious (individual flowers are either male or female, but both sexes can be found on the same plant) and are pollinated by Wind.It can fix Nitrogen. The common alder provides food and shelter to wildlife, with a number of insects, lichens and fungi being completely dependent on the tree. It is a pioneer species, colonising vacant land and forming mixed forests as other trees appear in its wake. Eventually common alder dies out of woodlands because the seedlings need more light than is available on the forest floor.

Suitable for: medium (loamy) and heavy (clay) soils and can grow in heavy clay and nutritionally poor soils. Suitable pH: acid, neutral and basic (alkaline) soils. It can grow in semi-shade (light woodland) or no shade. It prefers moist or wet soil. The plant can tolerate maritime exposure
Cultivation:
Landscape Uses:Firewood, Pest tolerant, Pollard, Screen. Prefers a heavy soil and a damp situation, tolerating prolonged submergence of its roots and periods with standing water to 30cm deep. Plants can also grow quickly in much drier sites, though they will usually not live for so long in such a position. Alders grow well in heavy clay soils, they also tolerate lime and very infertile sites. Tolerates a wide range of soils but prefers a pH above 6. Very tolerant of maritime exposure. Alder is estimated to tolerate an annual precipitation of 40 to 200cm, an annual average temperature of 8 to 14°C and a pH of 6 to 8. The leaves often remain green on the tree until November, or even later on young seedlings. The seeds contain a margin of air-filled tissue and are capable of floating in water for 30 days before becoming waterlogged. This enables distribution of the seed by water. The alder has a very rapid early growth, specimens 5 years old from seed were 4 metres tall even though growing in a very windy site in Cornwall. This species has a symbiotic relationship with certain soil micro-organisms, these form nodules on the roots of the plants and fix atmospheric nitrogen. Some of this nitrogen is utilized by the growing plant but some can also be used by other plants growing nearby. Nitrogen-fixation by trees up to 8 years old has been put at 125 kg/ha/yr., for 20 years at 56 – 130 kg/ha/yr.. Trees often produce adventitious roots from near the base of the stem and these give additional support in unstable soils. Trees are very tolerant of cutting and were at one time much coppiced for their wood which had a variety of uses. Alders are an important food plant for the caterpillars of many butterfly and moth species and also for small birds in winter.There are 90 insect species associated with this tree. There are some named varieties, selected for their ornamental value. Special Features:Not North American native, Naturalizing, Wetlands plant, Inconspicuous flowers or blooms.

Propagation:
Seed – best sown in a cold frame as soon as it is ripe and only just covered. Spring sown seed should also germinate successfully so long as it is not covered. The seed should germinate in the spring as the weather warms up. When large enough to handle, prick the seedlings out into individual pots. If growth is sufficient, it is possible to plant them out into their permanent positions in the summer, otherwise keep them in pots outdoors and plant them out in the spring. There are about 700,000 – 750,000 seeds per kilo, but on average only about 20 – 25,000 plantable seedlings are produced. Seeds can remain viable for at least 12 months after floating in water. Seeds germinate as well under continuous darkness as with normal day lengths. Air-dried seeds stored at 1 – 2°C retained their viability for two years. Seeds can however be sown immediately as soon as ripe. If you have sufficient quantity of seed, it can be sown thinly in an outdoor seed bed in the spring. The seedlings can either be panted out into their permanent positions in the autumn/winter, or they can be allowed to grow on in the seed bed for a further season before planting them. Cuttings of mature wood, taken as soon as the leaves fall in autumn, outdoors in sandy soil.
Medicinal Uses:
The bark is alterative, astringent, cathartic, febrifuge and tonic. The fresh bark will cause vomiting, so use dried bark for all but emetic purposes. A decoction of the dried bark is used to bathe swellings and inflammations, especially of the mouth and throat. The powdered bark and the leaves have been used as an internal astringent and tonic, whilst the bark has also been used as an internal and external haemostatic against haemorrhage. The dried bark of young twigs are used, or the inner bark of branches 2 – 3 years old. It is harvested in the spring and dried for later use. Boiling the inner bark in vinegar produces a useful wash to treat lice and a range of skin problems such as scabies and scabs. The liquid can also be used as a toothwash. The leaves are astringent, galactogogue and vermifuge. They are used to help reduce breast engorgement in nursing mothers. A decoction of the leaves is used in folk remedies for treating cancer of the breast, duodenum, oesophagus, face, pylorus, pancreas, rectum, throat, tongue, and uterus. The leaves are harvested in the summer and used fresh.

Research:
In a research study, extracts from the seeds of the common alder have been found to be active against all the eight pathogenic bacteria against which they were tested, which included Escherichia coli and methicillin-resistant Staphylococcus aureus (MRSA). The only extract to have significant antioxidant activity was that extracted in methanol. All extracts were of low toxicity to brine shrimps. These results suggest that the seeds could be further investigated for use in the development of possible anti-MRSA drugs

Other Uses:
Charcoal; Dye; Hedge; Hedge; Ink; Insecticide; Parasiticide; Pioneer; Shelterbelt; Soil reclamation; Tannin; Teeth; Wood.

Tolerant of clipping and maritime exposure, the alder can be grown in a windbreak or a hedge. The trees are very quick to establish and will grow at a rate of 1 metre or more per year when young. This is an excellent pioneer species for re-establishing woodlands on disused farmland, difficult sites etc. Its fast rate of growth means that it quickly provides sheltered conditions to allow more permanent woodland trees to become established. In addition, bacteria on the roots fix atmospheric nitrogen – whilst this enables the tree to grow well in quite poor soils it also makes some of this nitrogen available to other plants growing nearby. Alder trees also have a heavy leaf canopy and when the leaves fall in the autumn they help to build up the humus content of the soil. Alder seedlings do not compete well in shady woodland conditions and so this species gradually dies out as the other trees become established. Because they tolerate very poor soils and also produce nitrogen nodules on their roots, alders are suitable for use in land reclamation schemes. The plants can be used as a source of biomass. According to the phytomass files, annual productivity is estimated at 6 to 9 tonnes per hectare. The tree has yielded 11.8 tonnes per hectare per annum on pulverized fuel ash and annual productivity has been estimated at 8.66 tonnes per hectare, with 5.87 tonnes in wood, bark, and branches, 2.79 tonnes in foliage. Alder has been recommended for consideration for firewood plantations in Tropical highlands where unseasonable cold might destroy the red alder. The powdered bark has been used as an ingredient of toothpastes. Sticks of the bark have been chewed as tooth cleaners. An ink and a tawny-red dye are obtained from the bark. A green dye is obtained from the catkins. A pinkish-fawn dye is obtained from the fresh green wood. A yellow dye is obtained from the bark and young shoots. A cinnamon dye is obtained from the shoots if they are harvested in March. If they are dried and powdered then the colour will be a tawny shade. The bark and the fruits contain up to 20% tannin, but they also contain so much dyestuff (imparting a dark red shade) that this limits their usefulness. The leaves are also a good source of tannin. The leaves are clammy and, if spread in a room, are said to catch fleas and flies on their glutinous surface. Wood – very durable in water, elastic, soft, fairly light, easily worked, easily split. It is often used for situations where it has to remain underwater and is also used for furniture, pencils, bowls, woodcuts, clogs etc. It is much valued by cabinet makers. The wood also makes a good charcoal.

Known Hazards: Pollen from the common alder, along with that from birch and hazel, is one of the main sources of tree pollen allergy. As the pollen is often present in the atmosphere at the same time as that of birch, hazel, hornbeam and oak, and they have similar physicochemical properties, it is difficult to separate out their individual effects. In central Europe, these tree pollens are the second most common cause of allergic conditions after grass pollen.

Disclaimer : The information presented herein is intended for educational purposes only. Individual results may vary, and before using any supplement, it is always advisable to consult with your own health care provider.
Resources:
https://en.wikipedia.org/wiki/Alnus_glutinosa
http://www.pfaf.org/user/Plant.aspx?LatinName=Alnus+glutinosa

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