Tree Tips – why the leaves fall

Why the Leaves Fall

The turning of leaf color and eventual falling of leaves are a part of the trees’ strategy and preparation for winter.  Some trees, such as evergreens, have developed methods of winter survival. Deciduous, or broadleaf, trees have leaves that are thin and wide and are very vulnerable to cold and snow of winter, so removal of their leaves are important aspect of winter preparation.

As sunlight decreases, the tree begins to cut back on its parts more vulnerable to freezing, which are mainly its leaves.  Leaves are the food factory or kitchen of the tree, producing carbohydrates or food for the tree.  In doing this, trees need carbon, water, and oxygen to photosynthesize sugar for food.

However, as the temperature drops, the water in the leaf veins begins to freeze, cutting down photosynthesis in the leaf. To keep producing food the tree to use more energy. This food producing energy will be needed for plant growth in the spring. Additionally, some water transpires or escapes from leaf openings during photosynthesis causing more energy to be used to transport water from the roots to the leaves.  Consequently, water retention and nutrient loss are major concerns for the tree in winter. The tree begins storing these nutrients and water as it goes dormant for the winter.

A leafless tree in springtime also allows for easier windborne dispersal of pollen for seed propagation of tree species.

Another side benefit of leaf fall is the leaf litter on the ground or forest floor. This detritus provides vital organic matter and soil building structure and water retaining capacity in the soil.  This is why mowing over leaves on the lawn is encouraged, but don’t just leave fallen leaves sitting on the ground.

Raking leaves can be an unpleasant fall job, but Mother Nature has a reason for them being on the ground.

If you have a question about trees, feel free to contact the Vermilion Tree Commission by contacting Anne Maiden at the Mayor’s Office at or at 440-204-2402.  The Vermilion Tree Commission meets the second Wednesday of the month at the Ritter Public Library at 9:30 a.m.  The next meeting will be on November 8, 2017.


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