WRW #24: The Amazing Alder
The cache, a small camo-taped, pre-form tube is attached to a larger branch in a little thicket of small shoots growing from a multi-trunked coppiced stool of this incredibly useful tree.
It is the third cache in the Addingham High Mill to Farfield section of the WRW cache series, which here is along the Dales Way long distance path.
To reach the cache location: park in the High Mill parking area @ N 53 56.874 W 1 52.595 then head north following the Dales Way path into and through the Olicana cottages, then along the riverside trail to the cache.
What do Robin Hood, Venice, leather, electric guitars and clogs have in common . . . ??
The (common, black or European) alder (Alnus glutinosa) is one of around 30 species of tree in the birch family Betulaceae, and is native to most of Europe, southwest Asia and northern Africa. It is the only species native to the UK. It thrives in wet locations where its association with the bacterium Frankia alni (found in root nodules) enables it to grow in poor quality soils.
It is a medium size, short-lived conical multi-stemmed tree growing to a height of around 20m. 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 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. Its more usual habitat is forest edges, swamps and riverside corridors.
It is important to wildlife all year round and the seeds are a useful winter food for birds. Catkins provide an early source of nectar and pollen for bees, and the seeds are eaten by siskin, redpoll and goldfinch. Deer, sheep, hares and rabbits feed on the tree and it provides shelter for livestock in winter. It shades the water of rivers and streams, moderating the water temperature, and this benefits fish which also find safety among its exposed roots in times of flood. Its roots make perfect nest sites for otters.
It is food for larvae of a various butterflies and moths and is associated with over 140 species of plant-eating insect. It also hosts a variety of mosses and lichens which particularly flourish in the humid moist environment of streamside trees.
Some 47 species of mycorrhizal fungi have been found growing in symbiosis with the common alder, both partners benefiting from an exchange of nutrients.
As an introduced species, it affects the ecology of its new locality. It is a fast-growing tree and can quickly form dense woods where little light reaches the ground, and this may inhibit the growth of native plants. The presence of the nitrogen-fixing bacteria and the annual accumulation of leaf litter from the trees also alters the nutrient status of the soil. It also increases the availability of phosphorus in the ground, and the tree's dense network of roots can cause increased sedimentation in pools and waterways.
It spreads easily by wind-borne seed, may also be dispersed by birds and its woody fruits can float away from the parent tree. When the tree is felled, regrowth occurs from the stump, and logs and fallen branches can take root.
It is used as a pioneer species and to stabilise river banks, assist in flood control, purify water in waterlogged soils and to moderate the temperature and nutrient status of water bodies. It can be grown by itself or in mixed species plantations, and the nitrogen-rich leaves falling to the ground enrich the soil and increase the production of such trees as walnut, Douglas fir and poplar on poor quality soils. Although it can live for up to 160 years, it is best felled for timber at 60-70 years before heart rot sets in.
On marshy ground it is important as coppice-wood, being cut near the base to encourage the production of straight poles. It can withstand clipping as well as marine climatic conditions and may be cultivated as a fast-growing windbreak.
In woodland natural regeneration is not possible as the seeds need sufficient nutrients, water and light to germinate. Such conditions are rarely found on the forest floor and as the forest matures, alder trees in it die out.
It is also cultivated as a specimen tree in parks and gardens.
Due to its ability to withstand rot, the timber has been used in underwater foundations (much of Venice is 
built on alder piles) boats, sluice gates and water pipes. It is used for manufacture into paper and fibreboard, for smoking foods, for joinery (both as solid timber and as veneer, where its grain and colour are appreciated, and it takes dye well). It is valued in turnery and carving, in making furniture, window frames, clogs, toys, blocks, pencils and bowls. The wood also makes excellent charcoal and gunpowder. Its bark and wood (like oak and sweet chestnut) contain tannin and are used to tan leather. A red dye can also be extracted from the outer bark, and a yellow one from the inner.
Electric guitars, especially Fenders, have been built with alder bodies since the 1950s. Alder is appreciated for its claimed tight and even balanced tone, especially when compared to mahogany, and has been adopted by many electric guitar manufacturers.
It used to be the preferred wood for clogs and it was said that a few alder leaves placed in these before a long journey would cool the feet and prevent swelling!
Health: its pollen - as with that from birch and hazel - is one of the main sources of tree pollen allergy. Its bark has traditionally been used as an astringent, a cathartic, a hemostatic, a febrifuge, a tonic and a restorative. A bark decoction has been used to treat swelling, inflammation and rheumatism, as an emetic, and to treat pharyngitis and sore throat.
Ground up bark has been used as a toothpaste ingredient, and the inner bark can be boiled in vinegar to provide a skin wash for treating dermatitis, lice and scabies. The leaves have been used to reduce breast discomfort in nursing mothers and folk remedies advocate the use of the leaves against various forms of cancer. Its leaves are consumed by cows, sheep, goats and horses though pigs refuse to eat them.
Extracts from its seeds are active against all the eight pathogenic bacteria against which they were tested, which included Escherichia coli and methicillin-resistant Staphylococcus aureus (MRSA). This suggest that the seeds could be further investigated for use in the development of possible anti-MRSA drugs.
Mythology & symbolism:wet and swampy, alder woods (carrs) were thought to have a mysterious atmosphere. The green dye from its flowers was used to colour the clothes of outlaws like Robin Hood and also thought to colour the clothes of fairies! When cut the pale wood turns a deep orange like it is bleeding. As such many feared alders and the Irish thought it was unlucky to pass one on a journey. The Druids believed the alder to be symbolic of male/female balance as it has both female & male catkins on the same branch. It was also associated with courage, the evolving spirit, death & resurrection. In Celtic mythology the first human man was made from alder. For more alder mythology, see here.
See here for more information on this wonderful tree. See also short videos: A year in the life of an alder tree, and here (for ID)
Notable UK alders: girthiest 647cm @ Coniston, Cumbria; Tallest: 
32m in Wendens Rd, Audley End, Essex (see photo here)