Populus tremula

The aspen is a tall tree.

Its leaves are nearly round. The stems of the leaves are flat. This helps them shake in a light breeze.

In the spring, the tree grows flowers. These flowers make tiny seeds. The seeds have soft white fluff. This fluff helps the seeds fly in the wind. They can fall to the ground like snow. The tree can live for 200 years. It can grow in very cold places.

The aspen is a tall tree. It grows in many cool places. It lives in Europe and Asia. Some grow even north of the Arctic Circle.

Adult leaves are almost round. They have flat stems called petioles. These flat stems make leaves shake in the wind. This is why the tree is called the quaking aspen. Young leaves look different. They are heart-shaped and can be quite large.

In early spring, the tree grows flowers. These are called catkins. Male and female flowers grow on different trees. The female flowers make small capsules. These capsules hold many tiny seeds. The seeds are wrapped in soft fluff. This fluff helps the wind carry the seeds away.

Aspen trees are very hardy. They can live for 200 years. They grow fast for about 20 years. The wood is light and soft. People use it for paper and matches. It also helps make wood for power.

The aspen is a very special kind of poplar tree. It grows in many cool parts of the Old World. You might hear people call it the quaking aspen or the Eurasian aspen. This tree is a deciduous tree, which means it loses its leaves every year. It can grow quite tall and wide. The trunk of an adult tree can even reach a huge diameter.

There is a neat way these trees move in the wind. The adult leaves are nearly round and have a very flat stem. This stem is called a petiole. Because the petiole is flat, the leaves tremble in even a slight breeze. This movement is how the tree got its famous names.

In the early spring, the tree starts its life cycle. It grows flowers called catkins before the new leaves appear. These trees are dioecious, which means male and female flowers grow on different trees. The male catkins are green and brown. The female catkins grow small capsules in the early summer. Each capsule holds many tiny seeds inside soft, white fluff. When the capsules split, the wind carries the seeds away like snow.

Aspen trees have a very long history in the earth. Scientists have found fossils of these trees in the Kızılcahamam district of Turkey. These fossils are from the early Pliocene age. Today, these trees live in many places from Iceland to Japan. They can even grow north of the Arctic Circle in places like Norway.

These trees are very hardy and can live for 200 years. They grow very fast for the first 20 years of their lives. The aspen also spreads by sending out root sprouts called suckers. These sprouts can grow up to 40 meters away from the parent tree. This creates large groups of trees that are all part of one system. People use the light, soft wood for many things. It is used to make matches, plywood, and even writing paper.

Populus tremula is a significant species of deciduous poplar tree. It is commonly known by many names, including the Eurasian aspen, the European aspen, or the quaking aspen. These trees are native to the cool temperate regions of the Old World. They are considered substantial trees that grow both tall and broad. An adult tree can possess a trunk with a very large diameter.

The appearance of the tree changes as it matures. Young trees have smooth, pale greenish-grey bark with dark grey, diamond-shaped lenticels. As the tree gets older, the bark becomes dark grey and develops deep fissures. The leaves also show different shapes depending on the tree's age. Adult leaves are nearly round and slightly wider than they are long. They have a coarsely toothed margin. A key feature is the laterally flattened petiole, which is the leaf stem. This flat shape allows the leaves to tremble or "quake" in even a slight breeze.

Seedlings and root sprouts, also called suckers, have different leaf characteristics. These juvenile leaves are often much larger, reaching up to 10 centimeters. They are shaped like hearts or triangles and have less flattened petioles. The tree reproduces using wind-pollinated catkins that appear in early spring. Populus tremula is a dioecious species. This means that male and female catkins grow on entirely separate trees. The male catkins are patterned green and brown and shed pollen. The female catkins are green and mature in early summer. They produce 10 to 20 capsules, or seed pods, which can contain 50 to 80 seeds each. Each capsule holds numerous tiny seeds embedded in downy fluff. When the capsules split, the wind carries the seeds away using this fluff for dispersal.

Aspen trees have a deep history in the fossil record. Scientists have identified Populus tremula fossils in the Kızılcahamam district of Turkey. These fossils date back to the early Pliocene age. Today, the species has a vast distribution across Europe and Asia. It grows from Iceland and the British Isles in the west to Kamchatka in the east. It reaches as far north as the Arctic Circle in Scandinavia and northern Russia. In the south, it is found in central Spain, Turkey, North Korea, and northern Japan. It even occurs at one site in northwest Africa in Algeria.

The biology of the aspen allows it to thrive in many environments. It is a water and light demanding species. This means it grows vigorously in open areas after a fire or clear cutting. The tree is very hardy and can tolerate long, cold winters and short summers. It can reach an age of 200 years. For the first 20 years, the tree experiences fast growth. After this, crown competition increases and the growth speed decreases. Growth typically culminates at about 30 years of age. The tree also spreads through an extensive system of lateral roots. These roots produce suckers that can grow up to 40 meters from the parent tree. This process forms large clonal colonies.

Aspen trees are important to many different ecosystems. The species serves as a vital host for the hornet moth during its larval stage. Many other insect and fungi species benefit from the tree as well. It also provides a necessary habitat for various mammals and birds that require young forests. Because the leaves taste unpleasant, the trees are resistant to browsing by fallow deer. The wood itself is light and soft with very little shrinkage. This makes it useful for many industrial products. It is used for lumber, matches, plywood, and particle boards. It is also highly valued in the pulp and paper industry for making writing paper. Because it grows rapidly, it is also used for renewable energy production.

Humans have also interacted with the aspen through cultivation and breeding. The tree is found in many large gardens and parks. One specific cultivar is named 'Erecta,' which is a fastigiate variety with bright yellow autumn colors. This cultivar has received the Royal Horticultural Society's Award of Garden Merit. In North America, it is sometimes called the "Swedish columnar." Scientists have also worked to create hybrids. For example, the grey poplar, Populus × canescens, is a hybrid of the aspen and the white poplar. Forestry research institutes in places like Denmark have bred hybrids to increase timber production and improve disease resistance.