Alnus glutinosa

The alder is a big tree.

It likes to grow in wet mud. It can grow near rivers and ponds.

Tiny living things live on its roots. These helpers take food from the air. This helps the tree grow in poor soil.

The tree has small, round leaves. They are dark green on top. The leaves stay green late in the fall.

Its seeds are like tiny nuts. They have little pockets of air. This helps the seeds float on water.

Many animals love this tree. Birds eat the seeds for food. Many bugs live in its branches. It is a very helpful tree.

The common alder is a medium-sized tree.

It can grow up to 30 meters tall. This tree loves wet places. You can find it near rivers, ponds, and swamps. It is a pioneer species. This means it is one of the first trees to grow on empty land.

One special thing about the alder is how it eats. It lives with a tiny bacterium called Frankia alni.

This bacterium lives in small bumps on the roots. The bacterium takes nitrogen from the air. It turns it into food for the tree. In return, the tree gives the bacterium power. This helps the alder grow in poor soil.

The tree has round, dark green leaves. In the autumn, the flowers look like small cones.

These fruits hold seeds with tiny air pockets. These pockets help the seeds float on water. This lets the seeds travel far away. Many animals use the alder for food and shelter. Insects, birds, and even deer rely on it. The tree also helps fish by keeping river water cool.

The common alder is a medium-sized tree that plays a big role in nature.

It is often found in wet places like swamps, river edges, and ponds. This tree is known as a pioneer species. This means it is one of the first plants to move into empty land. As it grows, it helps other trees follow behind it to form mixed forests. However, it does not stay in deep forests forever. The seedlings need a lot of light to grow. Because the forest floor is often dark, the alder eventually dies out as the woods get older.

This tree has a very special way of working with tiny living things.

It lives with a bacterium called Frankia alni. This bacterium lives in small bumps, or nodules, on the tree's roots. The bacterium takes nitrogen from the air and turns it into food for the tree. In return, the tree gives the bacterium stored energy. This partnership helps the alder grow in poor soil where other trees might struggle. This process also makes the soil better for other plants to grow later.

People have studied this tree for a very long time.

A scientist named Carl Linnaeus first described it in 1753. Later, in 1791, Joseph Gaertner gave it the scientific name we use today. The name "glutinosa" comes from the Latin word for sticky. This is because the young leaves and buds have a sticky gum on them. Scientists have also found that extracts from the seeds can work against certain bacteria.

The common alder has many interesting features and numbers.

It can grow up to 30 meters, or about 98 feet, tall. The leaves are dark green on top and have a wavy edge. In the autumn, the flowers look like small, woody cones. These fruits hold seeds with tiny pockets of air inside. These air pockets help the seeds float on water for about a month. This allows the seeds to travel far away from the parent tree.

You might see the alder working in your own world. Its wood is used to make paper, fibreboard, and even items for smoking food. It can also be used to help keep river banks steady. The tree provides a home for over 140 types of insects. It also supports many fungi and lichens. Even fish benefit from the tree. The branches shade the water, which helps keep the temperature of the river cool and steady.

The common alder, scientifically known as Alnus glutinosa, is a medium-sized tree native to Europe, southwest Asia, and northern Africa.

It is a vital part of many ecosystems because it can grow in wet, nutrient-poor environments. It is often categorized as a pioneer species. This means it is one of the first trees to colonize empty or vacant land. As the alder grows, it improves the soil and allows other tree species to follow. Eventually, the alder dies out in mature woodlands because its seedlings require more light than the dark forest floor provides.

One of the most remarkable aspects of the common alder is its symbiotic relationship with a bacterium called Frankia alni.

This bacterium lives inside small bumps, or nodules, on the tree's roots. Through a process called nitrogen fixation, the bacteria take nitrogen from the air and convert it into a form the tree can use for food. In exchange, the tree provides the bacteria with carbon products created during photosynthesis. This partnership allows the alder to thrive in poor-quality soils where many other plants would fail. This process also increases the nitrogen and phosphorus levels in the surrounding soil.

The anatomy of the common alder is quite distinct. It can grow to a height of up to 30 meters, which is approximately 98 feet. Young trees usually grow straight up with a single main stem. As they age, they develop an arched crown with crooked branches. The bark changes as the tree matures, moving from a smooth, greenish-brown surface to a dark grey, fissured texture. The leaves are rounded with wavy, serrated edges. They are dark green on top and paler on the bottom. Because of the resinous gum on its buds, the species name "glutinosa" means "sticky."

The tree is monoecious, meaning it has both male and female flowers on the same plant. These flowers appear as catkins. The male catkins are long, reddish, and hang down. The female flowers are upright, green, and broad. In the autumn, these female flowers turn dark brown or black and become woody. They look similar to small conifer cones. These woody structures protect the seeds through the winter. In the spring, the tree releases small, winged seeds. These seeds have pockets of air that allow them to float on water for about a month.

The history of the common alder's classification involves several famous scientists. Carl Linnaeus first described the tree in 1753. At that time, he grouped it with the grey alder under the name Betula alnus. In 1785, Jean-Baptiste Lamarck identified it as a separate species named Betula glutinosa. It was not until 1791 that Joseph Gaertner accepted the separation of alders from birches. He moved the species into the genus Alnus, which is the name used today. In 2017, researchers discovered that some populations previously called Alnus glutinosa are actually separate species, such as A. lusitanica and A. rohlenae.

The common alder supports a massive amount of biodiversity. It is a host to over 140 species of plant-eating insects. It also supports many mosses and lichens, including the tree lungwort. Many fungi live in symbiosis with the tree, such as the alder roll-rim, which grows only with alders. The tree also provides food for wildlife, as birds eat the seeds in winter. Even fish benefit from the alder. The tree's branches shade rivers and streams, which helps moderate water temperatures. Its roots also provide safety for fish during floods.

Humans have used the common alder for many different purposes. The timber is soft and turns a pale red when cut. While it is not used for heavy construction, it is used for making paper, fibreboard, and joinery. It is also used for smoking foods and in various carvings. In ethnobotany, extracts from the seeds have been studied for their ability to act against pathogenic bacteria. Additionally, the tree is used in environmental management. It can be used to stabilize river banks, control floods, and help purify water in waterlogged soils.