When Do Leaves Start To Fall?

When does autumn start? It’s common to find many people who don’t know the answer to this question. However, it’s essential to indicate different ways to answer it. The meteorological autumn starts on September 1 in the Northern Hemisphere and ends on November 30. In contrast, the astronomical autumn begins on September 22 or 23 and finishes on December 21 or 22.

Meteorological seasons are based on the annual temperature cycles and the 12-month calendar. The four seasons are frozen (winter), cold (spring), hot (summer), and rainy (autumn or fall). Meteorologists typically use this definition of the seasons. On the other hand, the astronomical report is based on the Earth’s position to the sun.

For this reason, meteorological autumn starts on September 1 in the Northern Hemisphere. The leaves begin to change color and fall from the trees during this season. In contrast, the astronomical autumn starts on September 22 or 23 and finishes on December 21 or 22.

When Do Leaves Fall?

Every year leaves change color and fall from the trees. This process is called "leaf drop" or "leaf fall." The leaves start to change color in late September or early October. They reach their peak color in mid-October and continue to fall until December. The timing of leaf drop depends on the type of tree. Deciduous trees are trees that lose their leaves every year. Coniferous trees are evergreen trees that keep their leaves all year.

Most deciduous trees in the Northern Hemisphere lose their leaves in September or October. The process of leaf drop takes about six to eight weeks. Coniferous trees, on the other hand, keep their leaves all year. You will mostly find them in colder climates, such as mountains.

What Causes Leaves to Change Color and Fall?

The length of day and night changes in the autumn, which triggers the leaf drop process. The leaves of deciduous trees contain a pigment called chlorophyll. Chlorophyll helps trees make food from sunlight. The days are longer in the spring and summer, and there is more sunlight. This helps the trees produce more chlorophyll.

In autumn, the days become shorter, and there is less sunlight. As a result, trees produce less chlorophyll. The other pigments in the leaves, such as carotene and xanthophyll, become more visible. These pigments are yellow, orange, and red. That’s why the leaves of deciduous trees change color in autumn.

However, leaves fall because of a different process. The leaves are attached to the tree by a stem called the petiole. The petiole contains tiny tubes that transport water and nutrients from the roots to the leaves. In autumn, the tree produces a hormone called abscisic acid. This hormone signals the petiole to close the tiny tubes.

As a result, the leaves stop receiving water and nutrients from the tree. Without water and nutrients, the leaves cannot survive. The leaf cells begin to die, and the leaf starts to dry out. Eventually, the petiole detaches from the tree, and the leaf falls to the ground.


Understanding the science behind the leaf drop can help you appreciate the beauty of autumn. Even though the leaves are falling, the trees are preparing for winter. They are getting ready to start the cycle again in spring. Contact Long Island LeafGuard Gutter Company for more information on keeping your gutters clean this autumn.