Why Trees Lose Their Leaves

Leaf loss in trees occurs naturally and as a result of disease or stress.

All deciduous tree leaves change color and fall from trees in autumn, as the tree responds to cooler temperatures and less sun, according to the State University of New York. Health problems can also cause trees to lose leaves.

Fall

Trees use light as energy to produce food from carbon dioxide and water. As fall begins, leaves stop this process, turning yellow, orange and red as the green chemical known as chlorophyll breaks down. Leaf stems also develop a special layer of cells that cut the leaf off from the tree, allowing the leaf to fall or blow down.

Moisture

Trees require adequate moisture to grow and make food through the process known as photosynthesis. In times of drought, leaves wilt, turn color prematurely and fall off the tree, according to North Carolina State University. Leaf loss may also occur if trees receive excess water.

Temperature

Some trees lose their leaves as a result of low or freezing temperatures. Citrus trees often drop their leaves after a freeze, but they grow once again when warmer weather arrives in early spring, according to Texas A&M University.

Stress

Stress caused by many possible factors results in leaf loss in trees. Possible culprits include weed killers, shock from winter pruning or other poor maintenance, diseases such as wilt or some pest infestations.

References

• State University of New York: Why Leaves Change Color
• North Carolina State University: Trees: Damage
• Texas A&M: Home Fruit Production -- Citrus
• Texas A&M: Trees

Resources

• Illinois Forestry: Why Tree Leaves Turn Color in Autumn