Trees
Trees are unique living things
Image: Hamsterkiste
1 Trees are unique
A deciduous forest in spring
Image: Hamsterkiste
Trees can grow taller, heavier and older than any other living things on Earth. They grow very slowly and never move from where they are.
They cope with all kinds of weather and every season. They can stand alone or form a dense green forest with others. They grow on every continent, in the mountains as well as by the sea and on islands. They produce wood, which we use to build houses, furniture and toys, and to heat our homes.
With the help of sunlight, water, carbon dioxide and nutrients from the soil, trees sustain themselves. They provide a home for countless animals, large and small. And when they die, they create the basis for new life. They become humus, in which other plants can grow.
Find out:
- Why are trees unique?
2 Trees have roots
Trees are firmly anchored in the ground by their roots
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Trees are anchored in the ground by their roots. Some trees’ roots reach deep underground, while others spread their root systems closer to the surface. Although this provides less protection against strong winds, it allows them to thrive in rocky ground or nutrient-poor soil. Trees need a lot of water. Fine hairs on the outermost root tips absorb water distributed through the soil, along with essential nutrients. A tree’s roots extend underground about as far as its branches extend above ground. This area is known as the drip line. A lot of water drips down within this area, helping to nourish the tree.
Roots do more than support the tree itself. They also prevent the soil they grow through from being washed away or blown away by the wind.
Find out:
2. What are roots for?
3 Deciduous trees
Leaves of the American Oak
Image: Hamsterkiste
Trees need plenty of sunlight to grow and thrive. Deciduous trees capture this light with their leaves. Examples of deciduous trees include oak, beech, birch, hazel, lime, maple, and black locust. Water also evaporates through the leaves. Evaporation creates suction, drawing water upward against gravity through tiny channels in the bark. This is how the tree supplies itself with water. Tree leaves are mostly flat. Some have smooth, unlobed edges, while others have smooth edges with only a few notches. Still others are deeply lobed or made up of several parts. Some leaf shapes help rainwater drip off more easily or direct it toward the tree’s roots.
Find out:
3. Which types of trees are conifers?
4 Coniferous Trees
The trees’ needles also collect sunlight and regulate evaporation. Here are the branches of a larch.
Image: Hamsterkiste
Not all trees bear leaves. Some have long, thin, stiff needles. In our region, pines, firs, spruces, and larches are examples of trees with needles, which is why we call them conifers. Their needles also capture sunlight and regulate evaporation. Needles have tiny openings called stomata. Water evaporates through the stomata, but they can also close in extreme cold or heat. Leaves and needles take up a gas from the air called carbon dioxide. They produce another gas, oxygen, which is then released. Some conifers keep their needles all year round. They continually lose some needles while new ones grow at the same time. Only the larch sheds all its needles in autumn and grows new ones in spring.
Find out:
I4. Which trees are conifers?
5. Which conifer loses its needles in autumn?
5 Bark and bark
Beech trees usually have smooth bark
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The oak’s bark is fissured
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Trees have skin too. We distinguish between bark and outer bark. The inner bark is made up of particularly tough cells. It protects the tree from external damage, pests and frost. In some trees, the bark stays smooth, for example on the European beech.
Others develop a bark covered with deep cracks. The wood of conifers also contains sticky resin. It helps the tree seal injuries to its bark. Some trees can completely regrow their bark. One example is the cork oak in Spain and Portugal. Its bark grows especially thick. When these trees are 25 years old, they are stripped for the first time. The cork layer is removed and used to make wine bottle corks. A new layer of cork keeps growing on the tree.
Find out:
6. What is the “skin” of a tree called?
7. What can corks for wine bottles be made from?
6 Flowers and fruit
A chestnut’s blossoms
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Acorns are the fruit of oak trees
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Trees reproduce, too. Some produce flowers, in which pollen develops. These are tiny grains, also known as flower dust. Pollen reaches other flowers with the help of the wind, insects or other animals. This is called pollination. Pollinated flowers produce fruit, such as apples, chestnuts, nuts, acorns or beechnuts. New trees can grow from the seeds and fruits. For example, bees and other insects pick up pollen from one apple blossom and carry it to another. By contrast, the black alder produces elongated catkins in March or April, which also bear pollen. Small cones have formed nearby, and the wind carries the pollen to them. Fruits can then develop from them, too.
In other tree species, pollen grows on one tree, while flowers with pistils grow on another. These include, for example, willow, yew and poplar.
Find out:
8. What develops in the flowers of trees?
9. Who helps pollinate the trees?
10. What fruits grow on trees? Give some examples.
7 Trees grow old, thick and enormous
The summer lime tree of Schenklengsfeld is considered the oldest tree in Germany
Image: By Rainer Lippert - Own work, Public domain, https://commons.wikimedia.org/w/index.php?curid=2189589
Trees can live for a long time. Apple trees and birches live for about 100 years. Norway maples and hornbeams can reach 150 years. European beeches and black poplars can live for around 300 years. Scots pines and larches sometimes reach 600 years. The oldest native trees are lime trees and oaks. They can live for up to 1,000 years, and sometimes even longer. The oldest tree in Germany is said to be the summer lime in Schenklengsfeld, Hesse. It is estimated to be 1,200 years old. The oldest trees in the world grow in California. The bristlecone pine “Methuselah,” for example, is over 4,800 years old. Trees can also grow very tall if given enough time. Our oaks reach heights of around 30 to 40 meters. That is not very tall, however, compared with other trees. A giant eucalyptus measured in Australia once stood more than 132 meters tall. The tallest tree on Earth is currently a coast redwood in California. It is called “Hyperion” and stands 115.85 meters tall. A Montezuma cypress grows in Mexico, with a trunk circumference of 58 meters. The “General Sherman Tree” is also in California. It is only 84 meters tall and about 2,500 years old, but its trunk circumference is 31 meters.
Find out:
11. How long do native tree species live?
12. How tall can trees grow?