There are several things that could cause a tree’s leaves to turn yellow or fall off in the summer. Sometimes, it’s perfectly normal and nothing to worry about. But most of the time, insects or diseases, environmental factors, or things you’ve done (or not done!) to your tree can cause its leaves to turn yellow in the summer. All of these things can cause the tree to die back and fail to grow.
We explain why leaves turn yellow, what signs to look for, what’s probably wrong, and what to do about it so you can decide if your tree’s yellow leaves in the summer are a big deal.
When healthy green summer leaves start turning yellow or dropping early, it’s understandable to be concerned. Leaf color changes and leaf drop are often associated with fall, so it’s alarming to see these happening in the summer months.
While some minor yellowing is normal, extensive yellowing or defoliation in summer is almost always a sign that the tree is struggling with an environmental stress, pest or disease. This article covers the common causes of summer leaf yellowing, the risks it poses for trees, and what steps you can take.
Normal Leaf Yellowing in Summer
Before jumping to conclusions, it helps to understand what amount of yellowing is normal in summer.
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Deciduous trees should have full green foliage in summer. Some marginal leaf scorching may happen during heat waves.
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Evergreen trees naturally shed older leaves in summer after new growth hardens off. Some yellowing of older needles is expected.
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Yellowing mainly affects older interior leaves as the tree prioritizes new outer growth.
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Minor yellowing affects scattered branches vs. the whole crown.
Signs of Abnormal Leaf Yellowing
Watch for these signs that suggest your tree needs help:
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New leaves turn yellow instead of mature green
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Leaves yellow first at branch tips and edges
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Yellowing and browning affects a large percentage of leaves
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Excessive leaf drop with yellowed leaves falling
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Clustered dead branches with yellowed leaves
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Entire crown or individual branches look yellowed
When you observe these signs, it’s time to start diagnosing causes and remedies.
Common Causes of Summer Leaf Yellowing
There are several potential causes related to site, care, weather, pests and disease that can turn tree leaves yellow in summer.
Improper Watering
Both over- and under-watering cause leaves to turn yellow and drop. Trees need a constant supply of moisture without soaked soils. Insufficient water will cause drought stress, while excessive water limits root oxygen.
Poor Drainage
Soggy soil due to poor drainage has symptoms similar to overwatering, preventing roots from absorbing oxygen and nutrients.
High Temperatures
Scorching air temperatures can “cook” leaves, causing yellowing, browning and leaf drop. This is especially true for trees not adapted to hot climates.
Pest Infestations
Insects like aphids, scale, leaf miners and caterpillars cause damage that interrupts leaf processes. Affected leaves turn yellow then brown and drop.
Diseases
Fungal and bacterial diseases disrupt vascular tissues or leaf surfaces, leading to spotting, wilting and yellowing. Anthracnose, leaf spot and powdery mildew are examples.
Nutrient Deficiencies
Lack of nitrogen, iron, manganese and other essential elements causes chlorosis – yellowing from inadequate chlorophyll.
Compacted Soil
When soil becomes too dense, it prevents fine root penetration and functioning, which can lead to yellowing.
Herbicide Damage
Herbicide drift and exposure harms leaves, causing discoloration and drop. Avoid applying near trees.
Is Summer Leaf Yellowing Harmful?
Yellowing leaves are both a symptom and a survival mechanism for stressed trees. Within limits, it’s an adaptive process. But significant loss of leaves year after year depletes energy reserves for growth and disease resistance. It can take a cumulative toll on long-term health. Severe, extensive yellowing that affects an entire tree indicates an urgent situation.
What to Do About Summer Leaf Yellowing
If your tree shows troubling signs, take these steps:
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Identify any causes you can treat immediately, e.g. watering issues, drainage, mulch.
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Remove yellowed leaves and properly dispose of them if diseases are suspected.
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Rule out nutrient issues with a soil test and amend accordingly.
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Monitor for pests and treat early before populations multiply.
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Provide supplemental, deep watering during hot, dry periods.
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Cover susceptible trees to filter hot sunlight.
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Consider transplanting if a tree is in a unsuitable location.
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For severe cases, consult a professional arborist for diagnosis and care.
Taking quick, proactive measures to manage yellowing leaves can help ensure your trees remain vigorous during summer stress periods. With early correction, they can rebound resiliently.
Preventing Summer Leaf Yellowing
As always, prevention is the best cure. Here are proactive maintenance practices:
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Water – provide 1-2″ of water per week for trees, more during hot, dry periods.
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Fertilize – apply balanced, slow-release formula in early spring.
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Prune – remove dead branches, shape to encourage air flow.
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Monitor – check for pests and treat early before damaging populations build.
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Select trees suited for your climate and location.
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Provide shade if susceptible trees are in hot locations.
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Mulch around trees to conserve moisture and suppress weeds.
With preventive care, you can minimize leaf yellowing and keep trees thriving through summer stress. But if extensive yellowing does occur, be vigilant about identifying causes and taking corrective care.
When to Call an Arborist
If you suspect your tree is struggling with yellow leaves but can’t pinpoint a cause, have an arborist evaluate. A detailed inspection along with possible soil, tissue or pest sampling will provide answers. An expert can advise on treatment options, potentially correcting declining health before lasting harm occurs. Their diagnosis brings peace of mind if yellowing is minor or offers critical solutions for an ailing tree.
Summer leaf yellowing gives clues that a tree is enduring stress whether from growing conditions, pests, disease or its own anatomy. Some amount of yellowing is expected, but extensive color changes or leaf drop indicate a tree isn’t getting what it needs to thrive. With quick response to identify triggers and provide solutions, treasured trees can recover and continue enhancing our landscapes for years to come.
Normal Summer Yellowing of Tree Leaves
Every leaf has a lifespan—even on an evergreen tree. While deciduous trees drop their annual leaves each fall, evergreen trees have a different schedule. Deciduous trees lose their leaves every year, but broadleaf or coniferous evergreen leaves usually last three years.
Yellowing leaves in evergreen trees
Evergreens can drop leaves or needles throughout the year, depending on their species and their growing pattern. Once an evergreen tree has grown enough new leaves in the spring or summer, it can safely get rid of the old ones without hurting its energy stores or ability to make more energy through photosynthesis.
Evergreens like pine and arborvitae trees lose their needle-like leaves in late summer or early fall. Yews, on the other hand, get rid of their three-year-old leaves in late spring and summer.
Broadleaf evergreens like magnolia and holly lose their old leaves in the summer, after the new leaves have grown well.
Even if you see some yellowing leaves on an evergreen tree in the summer, everything is probably still going as planned.
Main Reason Leaves On Established Trees Turn YELLOW.
FAQ
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