- Education and Science
The Elegant Alder Tree
Notes from a Lancashire Countryman.
The common alder tree Alnus glutinosa belongs to the genus Alnus. It is thought that the name derives via the Anglo Saxon alor or aler. In Europe it is often known as the black alder while in the U.K. it is simply the common alder. North American species include the Mountain alder Alnus tenuifolia, White alder,A.rhombifolia and the Red alder A.rubra.
In Scandinavian mythology the alder is said to be the tree from which woman was created. Conversely in Ireland the mythology conveys to us that the tree created the first man. The alder tree came under attack from a fungal infection that destroyed many trees across Europe. It was first discovered in the south of England during 1993. The fungi was thought to have been imported by way of introduced species. The fungi belongs to the family Phytophthora which in days long ago caused the potato famine in Ireland. However, the reports of this disease seems to have lessened of late.
Alders have often been used as wind breaks. They are also employed by foresters to protect young more valuable timber saplings until they become established. Thus they are a good nurse crop.
Basic Biology of the Alder Tree
The root of the alder tree contains nodules that are able to transfer nitrogen from the air into the ground which then becomes nutrient rich. The roots may some times be clearly seen in alder carrs during the dry summer months when the water levels drop exposing the roots to be easily observed. The roots tens to have a reddish orange colour making them almost unmistakeable. At first glance one can be forgiven for thinking that the roots are diseased however, the bacteria is beneficial to the tree.
Nitrogen helps the growth of stems , leaves, flowers and the seeds. Without nitrogen growth of plants become stunted and the foliage may well turn a sickly yellow colour long before autumn occurs. There are other plants capable of transferring nitrogen from the air into the ground these include very common plants such as nettles and clover..
The bark is smooth grey at first becoming darker and more scaly with age. The twigs are hairless and of a grey brown colour.
Components of the Alder Tree
The trees thrive on wet ground for example by ponds and lakes and in boggy ground in general. They can achieve the height of 20-30metres but are generally smaller than this. They are thought to mature at 60 years of age and their lifespan is around 150 years. The young twigs and leaf buds and the young leaves when they first unfurl have a sticky resinous substance which protects them from insect damage. This fact gives rise to the trees species name of glutinosa.
The short stalked rounded leaves 6-12cm long are toothed.
The leaves become a dark glossy green colour as the summer progresses. because they are a tree of wet soils the leaves stay green well into the autumn and remain green when other trees are adorned in their autumn colours.
The flowers of the alder are wind pollinated catkins. Male and female grow on the same tree. The male catkins that appear in late winter and early spring are cylindrical but linear about 10cm long and of a reddish yellow colour. So many of these male catkins can be produced at this time that from a distance the tree can appear to be in full leaf. They hang down like tasseled ear rings from every twig. The female catkins are smaller being about 2cm long and are more tightly put together than the male catkins. Reddish at first soon becoming green and during the summer months swell into the familiar barrel shaped cone associated with the tree. Indeed these cones are the main way to identify alders for no other native British tree produces cones , all others that do so are coniferous such as pine and larch.
As the cones mature they become woody in nature and almost black in colour. The seeds contained within the cones are much sought after by siskins and other finches during the winter months when seeds of other trees and plants are hard to locate. The seeds have a cork like outer layer that allow them to float in water, thus being carries away from their arboreal mothers to lodge in some muddy bank to germinate.
The caterpillar of the alder moth is often associated with alder foliage they are easily identified by their striking yellow and black segments. The alder kitten moth may also be encountered, they too, are distinctive in their own way being squat and angular with two whip like tails.
THE WOOD---of alder is readily worked even when green. As the wood is worked it turns to a light orangy colour which found it favour with carpenters and furniture makers. The green wood was employed in the making of whistles and the beautiful sounding pan pipes in days gone by. It was also employed in the country cottage industry providing wood for spinning wheels. Because of its affinity and great resistance to water the wood was utilised in the building of bridge supports and canal lock gates.
It is not however, used in the construction of houses. Because of its high protein level it attracts the larva of a beetle. The larva are commonly referred to as woodworm. Indeed in olden days twigs and pieces of alder wood were placed in the drawers and chests of furniture made of more valuable timber such as oak to attract the wood worms to its protein , thus, leaving the oak alone. The wood was replaced at regular intervals. Alder is also used in the tanning of leather.
Medicinal uses. alder is considered to have tonic and astringent properties. A decoction of the bark is useful to bathe swellings and inflammations., especially as a gargle for sore throats. In has been stated that heated leaves in a muslin bag is efficient at relieving the symptoms of rheumatism. Culpeper, the 17th century herbalist, recommended that the fresh leaves be placed under the feet of those galled by travelling. They were said to refresh and moisten the feet of people who had been walking all day.