Alder

The alder is a tree or a shrub.

These plants like to grow near rivers. They also grow in wet lands.

Some alders grow very tall. Others stay small like a bush. Their leaves have bumpy edges. The wind helps carry their tiny seeds.

The tree helps the dirt. Small living things live in the roots. They take air and turn it into food for the soil. This makes the ground healthy for other plants.

People use alder in many ways. The wood can be used to make guitars. It is also used to make furniture. Some people use the bark for dye.

It is a very helpful tree for the Earth.

Alders are trees or shrubs in the birch family.

Most alders lose their leaves each year. Their leaves have bumpy edges. These plants often grow near rivers and wetlands.

Alders have special flowers called catkins. Some catkins are long and male. Others are short and female. The wind helps move pollen between them. The female catkins are woody. They look like small cones. When they are ready, they let out seeds. These seeds are very light. The wind carries them to new places.

These trees are very helpful to the Earth. They have a special bond with tiny living things. These are called bacteria. They live in small bumps on the roots. The bacteria take nitrogen from the air. They turn it into food for the soil. This makes the ground healthy for other plants. This helps new forests grow.

People use alder in many ways. The wood is used to make electric guitars. It is also used to make furniture. Some people use the bark to make red or yellow dye.

Alders are special trees and shrubs in the birch family.

They belong to a group called the genus Alnus. This group has about 35 different species. You can find them in the north temperate zone. Some even grow in Central America and the Andes mountains. Most alders lose their leaves each year. Their leaves are simple and have bumpy, serrated edges. They often grow near rivers, streams, and wetlands.

These trees use flowers called catkins to make seeds. The male catkins are long and thin. The female catkins are much shorter. Most alders are wind-pollinated. This means the wind carries pollen between the flowers. Some bees visit the flowers too. The female catkins are woody and do not fall apart. Instead, they stay closed like small cones. When they are ready, they open to release tiny seeds.

These seeds are very light so the wind can carry them easily.

Alders are very important for the soil. They have a special bond with a tiny living thing called Frankia alni. This is a type of nitrogen-fixing bacterium. These bacteria live in small, light brown bumps on the roots. The bumps can be as large as a human fist. The bacteria take nitrogen from the air and turn it into food. The tree gives the bacteria sugar in return. This process makes the soil much richer for other plants. Because of this, alders are often the first plants to grow in new areas after a fire or flood.

Scientists have found traces of alders for a very long time. The oldest fossil pollen found is from northern Bohemia. This pollen is about 58 million years old. The name alder comes from an Old English word, alor. The scientific name Alnus is the Latin version of that name. Different species have different sizes. The red alder can grow very large on the west coast of North America. The black alder is also very large and grows in Europe. However, the green alder is usually just a small shrub.

People use alder for many useful things. The wood is very popular for making electric guitars. Companies like Fender have used alder since the 1950s. It is also used to make furniture and cabinets. Because the wood is stable in water, people used it for pier pilings in Venice. Even the bark is useful. It can be used to make red or yellow dyes. Some people also use the bark for medicine.

It can help treat skin irritations and insect bites.

Alders are a diverse group of trees and shrubs belonging to the genus *Alnus*. They are members of the Betulaceae family, which is also known as the birch family.

This genus contains approximately 35 different species of monoecious plants. Being monoecious means that a single plant carries both male and female flowers. These plants are distributed widely throughout the north temperate zone. Some species even reach into Central America and the Andes mountains. Most alders are deciduous, meaning they lose their leaves every year. Their leaves are typically simple, alternate, and have serrated edges.

The reproduction of alders involves specialized flower structures called catkins.

On a single plant, you will find long, elongate male catkins and shorter female catkins. These flowers are primarily wind-pollinated, though bees occasionally visit them. A key difference between alders and birches is the structure of the female catkins. In alders, the female catkins are woody and do not fall apart when they mature. Instead, they stay closed and function much like the cones found on conifer trees. When they eventually open, they release tiny, light seeds called samaras.

These seeds are extremely lightweight, allowing the wind to disperse them easily across the landscape.

Scientists categorize the genus *Alnus* into three distinct subgenera. The first is Subgenus *Alnus*, which contains about 15 to 25 species. These trees often produce catkins in the autumn that remain closed throughout the winter. They eventually pollinate in the late winter or early spring. The second group is Subgenus *Clethropsis*, which includes only three species of trees or shrubs. The third is Subgenus *Alnobetula*, which consists of one to four species. Members of this subgenus, such as the green alder, are typically shrubs rather than large trees.

Some species, like *Alnus fauriei*, have not yet been assigned to a specific subgenus.

The history of the alder is quite long and well-documented in the fossil record. The oldest identifiable fossil pollen for *Alnus* was discovered in northern Bohemia. This pollen dates back to the late Paleocene, roughly 58 million years ago. The common name "alder" comes from the Old English word *alor*. This word is derived from the Proto-Germanic root *aliso*. The scientific name *Alnus* is the Latin equivalent of this name. This linguistic connection is seen in the French word *aulne* and the Spanish word *Alamo*.

Alders play a vital role in forest ecology through a process called nitrogen fixation.

They form a symbiotic relationship with a bacterium called *Frankia alni*. This bacterium lives inside light brown root nodules that can grow as large as a human fist. The bacteria take nitrogen from the air and convert it into a form the tree can use. In exchange, the alder provides the bacteria with sugars created through photosynthesis. This relationship allows alders to act as pioneer species. They can colonize disturbed areas like sites left by floods, fires, or landslides. For example, the Sitka alder adds an average of 3 kg of nitrogen to the soil per hectare each year. Red alder stands can supply as much as 50 kg of nitrogen annually to the soil.

Different species of alder show remarkable variations in size and habitat. The red alder (*Alnus rubra*) is a large tree found on the North American west coast. The black alder (*Alnus glutinosa*) is native to most of Europe and can also grow very large. In contrast, the green alder (*Alnus alnobetula*) rarely grows larger than a shrub. Alders are often found near wetlands, rivers, and streams. In some areas, dense groups of these trees are called alder carrs. Because their foliage and thin bark are not very flammable, alder groves can even serve as natural firebreaks in forests.

Humans have utilized alder for many practical purposes for thousands of years. The wood is highly valued in the music industry; Fender Musical Instruments Corporation has used alder for electric guitar bodies since the 1950s. This wood is prized for having a tight and evenly balanced tone. Because alder is very stable when submerged in water, it was used to make the wooden pilings for the foundations of Venice. The bark and wood also contain tannins, which are used in the traditional process of tanning leather. Additionally, the bark contains salicin, which is metabolized into salicylic acid in the body. Some Indigenous cultures have used red alder bark to treat skin irritations and insect bites.