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Common Alder

Alnus glutinosa

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Plant Profile

Flowering Months:
Betulaceae (Birch)
Deciduous tree
Life Cycle:
Maximum Size:
20 metres tall
Fens, fields, marshes, riverbanks, riversides, swamps, waterside, wetland, woodland.

Yellow, no petals
Yellow and pendulous (male catkins). Green and oval (female catkins). Male and female catkins present on same tree, and grouped in clusters of 3-8 on each stalk.
In winter the catkins turn into hard, dark, cone-like fruit which eventually release the seeds.
Deciduous. Round, dark green, leathery, smooth, serrated edges.
No parts of this plant are scented.
Frequency (UK):

Similar Species

Other Information


Alnus glutinosa, also known as the common alder or black alder, is a deciduous tree that is native to Europe and Asia. It belongs to the birch family and is known for its fast growth rate, attractive bark, and conical shape. Alnus glutinosa can reach heights of up to 100 feet (30 meters) and is often used as a shade tree or in naturalized areas. It is tolerant of a wide range of soil types and climates, including wet or flooded areas, and is often used to stabilize riverbanks and improve soil quality. Alnus glutinosa is generally hardy and low maintenance, but it can be prone to pests such as alder borers and aphids. The tree is also known for its medicinal properties and has been used traditionally to treat a variety of ailments. However, more research is needed to fully understand its effects and to determine the safety and effectiveness of using it medicinally.


The Common Alder, also known as Alnus glutinosa, is a deciduous tree that belongs to the birch family. It is native to Europe, Asia, and North Africa and can be found growing in a variety of habitats, including wetland areas, riverbanks, and coastal regions.

One of the unique characteristics of the Common Alder is its ability to grow in waterlogged soils. This is due to its ability to form a symbiotic relationship with a type of nitrogen-fixing bacteria that lives in its root nodules. This bacteria converts atmospheric nitrogen into a form that the tree can use for growth, allowing the Common Alder to thrive in otherwise inhospitable environments.

The Common Alder is a fast-growing tree that can reach heights of up to 30 meters. Its leaves are oval in shape and have a glossy green upper surface and a pale underside. In the spring, the tree produces small, greenish-brown flowers that are arranged in clusters. These are followed by small, woody cones that contain the tree's seeds.

The wood of the Common Alder is relatively soft and lightweight, making it a popular choice for a variety of uses. It is often used for furniture, flooring, and construction, as well as for smoking food and making charcoal.

The Common Alder is also an important tree for wildlife. Its seeds are an important food source for birds, such as the siskin and goldfinch, while its leaves provide food for the caterpillars of several moth species. The tree's bark is also a popular nesting site for birds and small mammals.

In addition to its ecological benefits, the Common Alder also has a rich cultural history. In many cultures, it was seen as a sacred tree, and was often associated with water and fertility. It was believed to have healing properties and was often used in traditional medicine.

In the Celtic culture, the alder tree was associated with the god Bran the Blessed, who was said to have been buried in an alder grove. In Norse mythology, the alder was believed to be the tree of the underworld, and was associated with the goddess Hel.

The Common Alder is also an important tree for the timber industry. Its wood is rot-resistant and was traditionally used for building houses, bridges, and boats. The wood is also used for making paper pulp and as a source of bioenergy.

The Common Alder is also an ornamental tree that can be used for landscaping. It can be planted in wetland areas and along riverbanks to stabilize the soil and provide habitat for wildlife. It is also a popular choice for park and garden settings, due to its fast growth and attractive foliage.

Another important aspect of the Common Alder is its ability to improve soil quality. The tree's root nodules contain nitrogen-fixing bacteria that can convert atmospheric nitrogen into a form that plants can use. This process helps to enrich the soil with nitrogen, making it more fertile and better able to support plant growth. Additionally, the tree's deep roots help to break up compacted soil and improve water infiltration.

The Common Alder is also a popular choice for riparian restoration projects. Its ability to grow in wetland areas and along riverbanks makes it an ideal tree for stabilizing the soil and reducing erosion. The tree's deep roots help to anchor the soil and provide a protective barrier against the erosive forces of water. Additionally, the tree's leaves and branches can provide shade, which helps to cool the water and create a more hospitable environment for aquatic life.

Another benefit of the Common Alder is its ability to provide habitat for a wide range of wildlife. The tree's leaves and seeds are a food source for many birds and mammals, while its bark is a popular nesting site for birds and small mammals. Additionally, the tree's canopy provides shelter and protection for many species of animals.

Another important feature of the Common Alder is its ability to tolerate and even thrive in polluted environments. The tree is able to tolerate high levels of heavy metals and other pollutants, which makes it an ideal choice for phytoremediation projects. Phytoremediation is the use of plants to clean up contaminated soils and groundwater. The Common Alder is able to absorb and store pollutants in its leaves, bark, and wood, which helps to reduce the concentration of contaminants in the soil and groundwater.

In terms of its growth habit, the Common Alder is a relatively short-lived tree, with a lifespan of around 60 to 80 years. It is also known to be a pioneer species, which means that it is one of the first trees to colonize an area after a disturbance. This makes it an important tree for reforestation and restoration projects.

In addition to its ecological benefits, the Common Alder also has a range of medicinal properties. Its bark and leaves have been used to treat a variety of ailments, including respiratory and skin disorders, as well as to relieve pain and inflammation.

In conclusion, the Common Alder is a versatile tree that has a wide range of benefits for the environment, humans and wildlife. It can improve soil quality, reduce erosion, and provide habitat for a wide range of animals. Its ability to tolerate and even thrive in polluted environments makes it a valuable tree for phytoremediation projects. It is also a pioneer species that can help to restore disturbed areas. Its medicinal properties make it a valuable resource for traditional medicine. If you are looking for a tree that can provide a wide range of benefits, the Common Alder is definitely worth considering.


Common Alder filmed on Winter Hill, Lancashire on the 27th August 2022.


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Reproduced by kind permission of the BSBI.

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