What’s Causing My Leaves To Fall In Late Summer/Early Fall?

Early Leaf Drop

If you’ve been seeing your tree’s leaves change color and fall from your tree already this season you’re not alone. Many homeowners have called in worried about early fall foliage and early leaf drop. Our Arborist have also noticed this occurring on many trees in the area, especially Oaks. They warn that early fall color and early leaf drop is a cry for help. 

In our area, you typically will start seeing the leaves turn at the beginning of October, hitting their peak right before the onset of November. Leaves changing color and dropping early in the year (September) is most likely a sign that your tree is sick/stressed. When trees are stressed, suffering from insect infestation, or infected with a disease, they may stop producing chlorophyll and start conserving energy. This speeds up the tree’s seasonal process making the leaves turn fall colors and drop earlier than usual.

Early Leaf Drop/Fall Color Caused By Heat Stress:

One of the most likely reasons your tree is experiencing early fall color and early leaf drop is because of heat stress. Despite having some days of cooler weather in August & September, the recent high temperatures in the 90s have caused heat stress on a lot of trees.

Heat stress occurs when trees lose water faster than they can replace it. Trees get their water from their roots which gets transported into the leaves of the tree. From there the water evaporates into the air from the underside of the leaves, a process called transpiration. When the weather is especially hot and dry, water is transpired very quickly causing the tree to become dehydrated. 

Although we’re just seeing the signs now, most heat stress damage has already occured back in the hottest days of summer. Even though the damage has already occurred you can lessen the stress on your tree going forward and improve your tree’s overall health by following our tips below. 

Early leaf drop - heat stress- transpiration

Water: Although the hottest days have passed it’s important to still water your tree. Watering your tree will make sure it stays hydrated so that it can recover from the heat stress it’s already experienced and keep it from experiencing any more if there are hot days ahead.

Feed With Bio-Stimulants: Bio-Stimulants contain a natural blend of sugars, bacteria, humic acid, sea kelp extract, and fungi. This mix feeds the soil and naturally fertilizes the tree, giving it what it needs to recover from heat stress. By introducing bio-stimulants to the critical root zone it will re-establish good soil composition and act as a multi-vitamin for your tree.  Fertilizing your trees with bio-stimulants strengthens the tree’s immune system, helps it recover from damage, and is one of the best preventative measures to keep your tree from getting sick.

Mulch: Mulching helps insulate the soil and protect the roots from extreme heat or cold. It also helps retain moisture keeping the tree hydrated and cool. Applying mulch can help stop further heat stress and will help your tree get the moisture & nutrients it needs to recover from heat stress in the past. Just make sure you don’t make one of the 5 Most Common Mulching Mistakes.

Soil Aeration:  Soil that is compacted can cause water to run off instead of being absorbed into the soil where it can reach the roots. If you’re watering your trees/shrubs but still seeing signs of heat stress, this may be the issue. You can combat this by having the soil in your tree’s critical root zone aerated. Our Arborists will use high-velocity air tools and techniques to properly aerate the tree’s critical root zone (CRZ) loosening the soil. This creates macro and micropore space, making room for water and nutrients to reach the roots.

Protect From Borers: At this time of year, borers are looking for stressed trees to enter and spend their winter in. If your tree is experiencing early leaf drop or has leaves changing colors already it’s an easy target for borers. Prevent borers from entering your susceptible, stressed tree by investing in a preventative borer treatment plan. 

Early Leaf Drop/Fall Color Caused By Disease:

Although most trees with these symptoms are suffering from heat stress, it’s possible that your tree has contracted a more serious illness causing it’s early leaf drop/fall color. Below are the most common diseases that could be causing your tree’s symptoms.  Keep in mind it can be very hard for homeowners to distinguish between trees affected by heat stress and those that are suffering from a disease or insect infestation. It’s best to contact an Arborist to take a look at the tree in order to get a proper diagnosis and health plan.   

Anthracnose:

Often found on ash, maple, oak, sycamore, and dogwood trees, Anthracnose is a fungus that can cause leaves to turn brown or yellow and fall from the tree prematurely. Anthracnose is more common in areas where there have been a wet spring and summer. Leaves infected with Anthracnose will typically have brown blotchy spots instead of being all one color. If your tree has been well hydrated all summer but is still suffering from early leaf drop and brown/yellow leaves, Anthracnose could be the issue. 

Anthracnose on Ash Tree Leaves

Bacterial Leaf Scorch: 

Common on Oaks, Elms, Sycamore, Sweet Gum, Bacterial leaf scorch clogs the tissues that transport water from the tree’s roots to the canopy. This dehydration causes the tree to appear to be under drought/heat stress even when it has access to enough water. If left untreated this disease will cause dieback, secondary invaders, branch death, and ultimately death. It can be hard to distinguish between Bacterial Leaf Scorch and heat stress but there are a few clues you can look for. With Bacterial Leaf Scorch browning at the edge of the leaf is typically irregular and the symptoms begin on the oldest leaves/branches while young leaves remain green. With heat/drought stress you will first see symptoms on the youngest leaves (leaves at the tips of branches) and the edge of each leaf will be evenly brown. 

Bacterial Leaf Scorch - Early Leaf Drop
Bacterial Leaf Scorch On Red Maple

If you’re having issues with heat stress or any of the diseases we mentioned above, we can help! Give us a call at 703-573-3029 to schedule a consultation with one of our Arborists, or book online using our online booking system. Our Arborist will be able to diagnose the issue causing your early fall color or early leaf drop and provide you with the best plan to keep your tree healthy. 

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Samantha Huff

Samantha Huff is the marketing coordinator at RTEC Treecare. She enjoys learning about the technical aspects of trees and the insects and diseases that prey on them. She hopes that these articles can help homeowners gain control of their tree and shrub maintenance by being aware of the signs and symptoms of unhealthy trees.
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