Tree Leaves Turning Yellow and Falling Off in Summer

Tree Leaves Turning Yellow and Falling Off in Summer

Trees and other plants are considered healthy if they have glossy, green leaves and firm stems and branches. While the changing of leaves is something to look forward to during the fall season, sometimes trees can lose their leaves during summer. Discoloration of tree leaves, such as when leaves turn yellow, is another cause for concern. 

Why Are My Tree’s Leaves Turning Yellow and Falling Off in Summer?

Watering issues 

Tree leaves tend to turn yellow because of either overwatering or underwatering. Once trees are dehydrated, the leaves turn yellow as they struggle to conserve water. You can ascertain the moisture level by sticking a screwdriver into the soil. If you have a hard time pushing it in, this could indicate that the tree is thirsty and requires deep watering. 

If the screwdriver test indicates that there is moisture in the roots, you should try watering less. Overwatering can harm the tree as it saturates the roots and soil, resulting in yellowing leaves. 

Too much or too little water could also result in premature shedding of leaves. If the summer season brought drought-like conditions, trees could lose their leaves to counter the stress of low water conditions. 

Similarly, too much water due to too much rain could also lead to yellowing leaves that fall off in summer. Too much water suffocates the roots, causing stress and loss of foliage.  Make sure you are not soaking the soil too much when you water your trees.

Insects or illness 

Insects or summer pest infestations could be the culprit of yellowing leaves and premature leaf drop. Pests like aphids affect tree species in certain regions and can do great damage to young and newly planted trees. Leaves may wilt and drop off as these pests suck the sap from the trees. 

Inspect the trees and branches, and check for holes in the tree trunk. Any signs of molds or blotches could indicate a fungal disease and you may have to consult an arborist to determine the disease. You may also opt for a tree risk assessment to identify diseases as well as the recommended treatment. 

Nutrient deficiency 

Trees require nutrients that are essential for their health and growth. Essential micronutrients include zinc, copper, iron, manganese, silicon, boron and molybdenum. There are also macronutrients, such as nitrogen, calcium, magnesium, sulfur and potassium, which are required in larger amounts and comprise a larger part of plant tissues.  A deficiency of these nutrients could result in yellow spots or leaves turning yellow, brown or black.

Too many leaves to support due to a crowded canopy

Trees tend to shed leaves early and fall off in summer to prevent their branches from being damaged by the weight of extra leaves. This happens when trees grow too fast and produce an abundance of leaves. With crowded tree canopies, trees may also be losing leaves to conserve water. This is usually the case in hot and dry climates where water is scarce and not enough to sustain the leaves. 

If your cultivated trees are not suffering from too much foliage loss, you could try adjusting your watering schedule. Supplying them with more water could halt the leaf loss, but you still need to keep an eye on the situation to avoid any issues. 

Other Reasons for Tree Leaves Turning Yellow and Falling Off in Summer

Too much shade 

Sunlight deficit could damage your trees as leaves are unable to photosynthesize. Sun-loving trees struggle when planted in the shade, while those that prefer shade will have burnt-looking yellow leaves when grown in full sun. Always select the right tree variety or species for the right place. 

Allow your sun-loving trees more sun by removing or pruning nearby trees. If some trees are getting too much sun, be sure to provide some shade such as a shade cloth or a structure to filter the sunlight. You can also transplant young trees to a more suitable area or remove the tree entirely so that you can still save it.

Herbicide damage 

Herbicide drift could damage or kill leaves and may result in yellowing. Apply herbicides only in calm conditions if you are using them in your garden or lawn. Do not spray herbicides near vulnerable trees or shrubs. 

High temperatures 

Tree leaves may turn yellow and eventually drop off because of heat stress brought about by high temperatures. You may have to seek the help of tree professionals to identify heat stress in trees.

When leaves turn yellow in summer, you should mulch and fertilize, as well as performing careful pruning and correct irrigation for your trees. Being able to identify the reasons for the discoloration will also help you treat them correctly so they are more able to recuperate.


Tree leaves turning yellow and falling off in summer could be a cause for alarm, as they normally mature and fall off during the autumn or fall. Common reasons for this occurrence include overwatering or underwatering, and nutrient deficiencies. However, it could also be due to disease, pest infestation, or an over-crowded tree canopy.

Image: / Meindert van der Haven