When and why do leaves fall from trees in autumn?

Every event and phenomenon occurring in nature has meaning and benefit. Even the falling of leaves remains significant for ecology and natural processes. When they fall into the soil, they become food for new plant and animal life. Fallen leaves also provide excellent frost protection for tree roots.

When and why do leaves fall from trees?

It's generally accepted that leaves fall from tree branches en masse only in the fall. Sometimes leaves fall throughout the year when climate change occurs:

• temperature changes;
• reduction in day length;
• dry weather.

Throughout the year, leaves fall due to disease and pest damage. The nearby chemical industry also causes trees to lose their crowns.

Leaf fall occurs in all plants without exception, even indoor ones. Even evergreen conifers periodically shed their needles.

Duration of daylight hours

Daylight hours gradually shorten in autumn. As daylight dwindles, leaf blades produce less chlorophyll. This pigment is responsible for the green color of leaves. It absorbs light and converts it into nutrients.

Due to the reduction in chlorophyll, photosynthesis slows, and the production of sucrose (an element used by plants for food) decreases. To avoid dying from lack of nutrition, trees gradually begin to shed their leaves.

Damage

Over the summer, leaves deteriorate and fall in the fall. They can be damaged by insects, diseases, or simply wear out. By the end of summer, the tree is ready to renew itself. In the fall, cold weather sets in, and the foliage is once again stressed. They suffer from cold winds, rain, and temperature fluctuations. All these factors cause the leaves to change color and fall.

Over the summer, many harmful substances accumulate in the green mass. Excess salts and metabolites accumulate there. To cleanse itself and remove unnecessary substances, the tree sheds its leaves for the winter.

Cold climate

In autumn, all vegetation begins to prepare for the cold winter period. To survive the winter, they require moisture and nutrients. To conserve these nutrients, plants shed their leaves. This process of leaf shedding is a natural, cyclical phenomenon that does not harm the trees.

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Accumulation of nutrients

During the winter cold, trees require nutrients for nutrition. During the summer and fall, plants accumulate the necessary nutrients.

First, chlorophyll is broken down into nutrient-rich energy substances. This is why leaves lose their green color, as the green pigment that absorbed daylight during the summer is lost from the leaf blades. The leaves first turn yellow or red, and the trees will later shed them.

Separating leaves from a tree

In summer, leaves are firmly attached to the branches on which they emerge. But gradually, a corky layer forms between the branch and the base of the petiole. It is at this point that the leaflets separate. For this reason, it is much easier to remove leaves from the branches in the fall than in the summer.

Once the cork layer has fully formed, the foliage loses its connection to the parent tree. Any mechanical stress (wind, rain, or other natural factors) causes the leaves to fall. Therefore, not all leaves have time to turn yellow. The remaining leaves gradually fall off under their own weight.

What happens after the leaves fall?

After trees shed their leaves, they enter a state of suspended animation. It's like a deep sleep. Plant growth ceases, and crops simply rest until spring. All the energy and nutrients accumulated over the summer are gradually and sparingly used.

Leaves that remain on the ground after the leaves fall protect the root systems of the parent plants. They act as a kind of blanket, preventing frost damage. Gradually, the leaves turn into nutritious humus, which nourishes the plants awakening from winter dormancy in the spring.

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Dry weather

Leaves obtain moisture through their roots. However, during hot days, moisture evaporates from the leaf blades. During dry periods, the tree sheds some of its leaves to survive and conserve essential moisture.

The benefits of fallen leaves

People tend to think of fallen leaves as natural debris that should be cleared away in the fall. But no natural phenomenon happens without a reason, so the autumn carpet has significant benefits that shouldn't be overlooked.

1. Fallen leaves are a natural fertilizer. They decompose quickly, enriching the soil with nutrients. People have learned to use leaves to nourish their garden plots. There is a special technology for processing fallen leaves to create nutritious compost.
2. Twigs and cuttings decompose much more slowly than leaf blades. They improve the soil structure, making it looser.
   
3. Beneficial bacteria and microorganisms living in the soil feed on leaf litter. In the spring, plants feed on the waste products of these plants.
4. The fallen layer becomes a natural, warm shelter for plants throughout the winter. The root system is reliably protected, and the soil beneath this blanket doesn't freeze and remains loose and moist.
5. When leaves are shed, pollination of flowering plants becomes more efficient. When branches are bare, there are no obstacles for the dispersed pollen. It spreads over a larger area and reaches more trees.

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But if trees grow in an ecologically polluted area, with a lot of traffic or a chemical plant, leaves in such areas absorb and accumulate hazardous gases and heavy metals over the summer. These gases later become hazardous themselves, leaching into the soil and water. In such areas, fallen leaves should be collected and burned.

Trees that don't lose leaves

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Not all trees shed their leaves for the winter. These are called evergreens. Conifers remain green all the time. Their needles fall once every two to three years, but this isn't noticeable to humans; it happens gradually. A tree never loses its entire branching surface.

Evergreen trees retain their leaves throughout the year because they are not affected by cold. A special wax coating protects them from frost. The cells contain a special antifreeze substance that prevents the plant from freezing. Deciduous trees, on the other hand, are very sensitive to cold snaps. Therefore, when the weather gets cold, these trees shed their leaves for the winter.

The shedding of leaves by trees in autumn is a natural part of the biological cycle. Fallen leaves ensure their continued existence the following year. This process helps trees adapt to weather conditions, conserve moisture, and survive cold winters.