Swamp-dweller, water-lover. The wood of this tough tree doesn’t rot when waterlogged, instead turning stronger and harder.
ALDER TREE STATISTICS
- Status:native deciduous tree
- Height:large (up to 35m)
- Girth:potentially to 5–6 metres
- Longevitypotential for long life (250+ years)
The common alder grows in riverbanks, in fens, and in damp forests. Its exposed roots offer fish with cover, while its rounder leaves supply food for water insects.
Mature conical trees may reach a height of roughly 28m and survive for approximately 60 years.
The bark is black, fissured, and usually lichen-covered. Twigs have a light brown stem that is speckled and becomes crimson at the top. Young twigs are rough to touch.
The Common Alder (Alnus glutinosa) is native to the UK, Europe, Western Asia, and North Africa. It grows naturally in moist settings like river banks and lake edges, but it is now being planted in many urban areas. It is commonly used in reclamation efforts since it, like other Alders, can provide nitrogen to the soil. The tree is comparable to two other Alders found in cities: the Grey Alder and the Italian Alder. Alder is identified by its notched leaf, male cone-like catkins, and female cone-like catkins that are in between the other two in size.
ENVIRONMENTAL RELATIONS | ALDER TREE
The Alder, the most prevalent tree species in riparian forests, is significant in these woods around streams and lochs. Because it is a deep-rooted plant, it contributes to maintaining the soil on river banks and lessens the impacts of erosion. Fish can find cover and safety from predators in exposed alder root networks in the water. Salmon and brown trout, among other fish, profit from the shade that alder foliage offers. In water, its leaves degrade quickly. Invertebrate larvae including caddisfly, stone, and water beetle larvae may eat them. These in turn support the aquatic food chain. These invertebrates are tasty to larger creatures like fish. Alder roots can be used by otters to locate secure locations for breeding and resting.
Alder and the bacteria Frankia alni have a significant symbiotic interaction. On the tree’s roots, frankia lives and grows in nodules. This bacteria fixes nitrogen by absorbing it from the air and giving it to the tree. Alder then gives the bacteria the carbon it produces through photosynthesis in exchange. This connection enables alder to increase the soil fertility in the areas where it grows. As a pioneer species, it provides nutrients to the successional species that come after.
Various moss and lichen species may be seen growing on the bark and branches of mature alder trees. On alder, tree lungwort and other lichens that love wetness are fairly prevalent. This is owing to the fact that it thrives close to rivers and streams, where spray regularly causes the air to be humid.
47 different mycorrhizal fungus species may grow on alder. Numerous plants and fungus develop mycorrhizal connections. The flow of nutrients, which neither partner can directly access, is beneficial to both parties. Some fungus exclusively associate with alder in this way. The brown roll-rim is one illustration of this. After the alder catkins have fallen to the ground in the spring, the brown cup fungus begins to bear fruit.
A unusual mould called Taphrina amentorum thrives in the blossoms and seeds of immature alder catkins. As the cones grow, galls develop and become harder.
Alder leaves develop galls because of a mite called Eriophyes. On the top surface of the leaves, these galls appear as elevated pustules. The mite feeds on sap that it suckers from the tree’s cell tissue and can range in hue from mild yellow-green to deep crimson.
Over 140 insects that feed on plants have called alder home. One of these is the sawfly of the striped alder. The May highflyer is one of the few moths in Scotland that solely consumes alder. Its larva resides in a hut constructed from two leaves that have been stitched together with silk. In England, a wider variety of moths are linked to alder. One of these is the alder kitten moth, which is absent from Scotland.
Like other tree species in Scotland, alder is consumed by red deer. This hinders the tree’s normal regrowth in many Highlands locations. Domestic sheep have the same impact nationwide. The most significant danger to alder’s existence is the algae-like Phytophthora. This can result in a disease that, if untreated, might lead to the widespread extinction of alder trees.
Because it is the most prevalent tree in river woods, which frequently serve as biological bridges between various forest sections, alder is a significant species in the Caledonian Forest. The health of the land and the rivers depends on its survival and growth.
WHERE CAN I FIND AN ALDER TREE?
The Alder is indigenous to virtually all of continental Europe (excluding the extreme north and south), as well as the United Kingdom and Ireland. It thrives in damp, chilly environments like as marshes, wet woods, and streams, where its roots aid in soil erosion control.
It may also be found in drier settings, such as mixed woodland and forest margins. It grows swiftly from seed and colonises barren ground quickly. Because of its connection with the nitrogen-fixing bacteria Frankia alni, it can thrive in nutrient-depleted soils where few other trees can.
Alnus is a genus with 30 species worldwide. They inhabit the North Temperate Zone, as well as North, Central, and South America. The sole species in the genus that is endemic to the United Kingdom is A. glutinosa.
ALDER TREE WILDLIFE VALUE
The Alder is eaten by the larvae of various moths, including the alder kitten, stone hook-tip, autumnal, and blue-bordered carpet moths. Catkins give early nectar and pollen to bees, while the seeds are consumed by the siskin, redpoll, and goldfinch.
Alder woodland’s damp conditions are suitable for a variety of mosses, lichens, and fungi, as well as the little pearl-bordered fritillary and chequered skipper butterflies and various crane fly species. Otters enjoy building their nests among the roots of alder trees.
MYTHOLOGY AND SYMBOLISM OF ALDER TREE
Because they were moist and marshy, alder forests, or carrs, were supposed to have a mystical vibe.
The green dye from the blooms was used to tint and disguise the clothing of outlaws like Robin Hood, and it was also considered to colour the clothing of fairies.
When sliced, the light wood becomes a rich orange, creating the image of bleeding. As a result, many people hated alder trees, and crossing one on a journey was considered unfortunate by the Irish.
ALDER TREE APPLICATIONS
The Alder wood, which is soft and porous, is only durable while wet, and its usefulness to humans is largely on its resistance to rotting in water. It has historically been used to make boats, sluice gates, and water pipelines. Alder wood is increasingly utilised in the production of timber veneers, pulp, and plywood.
For egg laying, female woodworms are considered to prefer alder to other woods. Traditionally, alder branches were trimmed and placed in cupboards to prevent woodworm from depositing eggs in the cabinet timber.
The Alder coppice wood burns efficiently and creates excellent charcoal and gunpowder. Nitrogen-fixing nodules in the roots of old industrial wastelands and brownfield areas condition the soil and promote soil fertility. Alders are also utilised to help prevent floods.
It was originally believed that placing a few alder leaves in your shoes before a long travel would keep your feet cool and avoid swelling.
Much of Venice is built on alder piles due of their water resilience.
THREATS AND CONSERVATION
Phytophthora has infected certain alders in the United Kingdom. Broadleaf tree species are prone to Phytophthora infections. However, it was assumed to be uncommon on alder until the discovery of a novel hybrid strain that produces root rot and stem lesions.
The disease, also known as alder dieback, is more evident in the summer because the infected alders’ leaves are disproportionately tiny and yellow, and they frequently fall prematurely. Infected tree tops feature dead twigs and branches. They may also have a disproportionately large number of cones, indicating stress. Sometimes trees perish rapidly, and sometimes they decay gradually. Brown, rusty patches on the bark and bleeding from the bark are symptoms. When revealed, the reddish, mottled inner bark contrasts with the whitish tone of healthy bark.