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Most homeowners expect to see brown tree leaves during the fall and winter. But nothing will stop you in your tracks like the sight of brown foliage on one of your beloved trees during the summer.
And while you’d never consider brown leaves a “good” thing in the summer, it doesn’t necessarily signal the imminent decline of your tree, either. The key is to identify the cause of the brown foliage and take the steps necessary to correct the problem, when possible.
We’ll share a few of the most common causes of brown summer leaves below, so you can get your tree the help it needs.
15 Common Causes of Brown Summer Foliage in Southeast Michigan
There are dozens of reasons your tree may be producing brown leaves during the summer, but the following 15 are among the most common and noteworthy.
1. Moisture Deficit
Extended dry periods are one of the most common reasons trees develop brown leaves during Southeast Michigan summers. Even established or “drought-tolerant” trees can struggle from prolonged droughts, especially when high temperatures, compacted soils, and turf competition exacerbate the problem.
2. Heat Stress
Even when rainfall is plentiful, high summer temperatures can make it difficult for a tree to extract enough moisture from the soil to offset that which is lost to transpiration. This problem tends to be most common in urban landscapes that are surrounded by pavement, reflected heat, and poor soils.
3. Wind Desiccation
Hot, dry winds can trigger the same kind of water stress that high temperatures do, as they’ll rapidly pull moisture from leaves faster than roots can replace it. This kind of browning is often most noticeable on exposed sides of the canopy or in recently transplanted trees with limited root systems.
4. Soil Compaction
Compacted soils restrict oxygen availability and limit root growth, making it difficult for trees to absorb water during summer heat. In Southeast Michigan, heavy clay soils combined with foot traffic, mowing equipment, or construction activity commonly contribute to chronic leaf scorch and canopy thinning.
5. Grade Changes
Adding or removing soil around trees can significantly damage roots and disrupt normal water and oxygen movement. Trees may not decline immediately, but browning leaves, sparse canopies, and branch dieback often begin appearing within a few seasons after grading work or construction.
6. Salt Injury
Road salt and deicing products can accumulate in the soil and interfere with a tree’s ability to absorb water properly. This kind of browning often occurs along leaf edges and tips, and it is particularly common on trees growing near roads, sidewalks, and parking lots.
7. Anthracnose
Anthracnose is a fungal disease that commonly affects sycamores, oaks, maples, and ashes during cool, wet springs. Infected leaves may develop irregular brown blotches, curling, or premature drop, and stressed trees can continue showing symptoms well into summer.
8. Verticillium Wilt
This soil-borne fungal disease attacks the vascular system of susceptible trees, including maples, smoke trees, catalpas, and others. Symptoms often include sudden browning, wilting, or dieback on individual branches, especially during periods of summer heat and drought stress.
9. Oak Wilt
A disease that will strike fear into the heart of any homeowner, oak wilt is a highly destructive vascular disease that can cause leaves to brown rapidly from the edges inward during the growing season. Red oak species are especially vulnerable and may decline or die within a single season once infected.
Tree-Care Pro-Tip: Except when necessary for safety reasons, never prune oak trees between April and October, as pruning wounds can attract the beetles that spread oak wilt.
10. Emerald Ash Borer
Emerald ash borer (EAB) larvae feed beneath the bark of ash trees, disrupting the tree’s ability to move water and nutrients. As the infestation progresses, the tree’s leaves may thin, wilt, or brown prematurely, often beginning in the upper canopy and progressing downward.
11. Spider Mites
Spider mites are tiny sap-feeding pests that become especially active during hot, dry weather. Infested leaves often develop a dull, “stippled” appearance before turning completely bronze or brown. Spider mites are most problematic for spruces and arborvitae, as well as many landscape plants.
12. Girdling Roots
Roots that circle or press against the trunk can gradually restrict water and nutrient movement throughout the tree. Over time, affected trees may develop undersized leaves, canopy thinning, and chronic summer browning despite otherwise adequate growing conditions.
13. Dutch Elm Disease
Dutch elm disease (DED) spreads through elm bark beetles and root grafts and kills by preventing water from flowing properly through infected trees. The leaves on infected trees typically turn yellow, curl, and then brown rapidly. These symptoms often begin on individual branches.
14. Two-Lined Chestnut Borer
Two-lined chestnut borer is a native pest that commonly attacks stressed or drought-weakened oak trees. It causes leaf browning and canopy thinning, which often begins in the upper crown. Severe infestations can lead to progressive branch dieback and general decline.
15. Bacterial Leaf Scorch
Bacterial leaf scorch is a disease that interferes with water movement inside the tree, causing leaf margins to brown while inner tissue remains partially green. Symptoms frequently worsen during hot weather and are commonly seen on oaks, maples, sycamores, and elms.
Brown Tree Leaves in the Summer: A Quick-Reference Table
Many of the causes of brown tree leaves during the summer cause relatively similar symptoms. That’s part of the reason it’s always wise to contact a professional arborist, who has the skills and experience to determine what is causing your tree’s problem.
However, the following table lists some of the best ID characteristics for the causes discussed above, as well as the relative danger the issue represents.
| Cause | Primary Diagnostic Criterion | Relative Risk |
| Moisture Deficit | Browning begins at the tips and margins across the entire tree simultaneously. | Moderate |
| Heat Stress | Scorching primarily on the south or west sides of the canopy. | Low |
| Wind Desiccation | Damage localized to the windward side; leaves appear scorched. | Low |
| Soil Compaction | Reduced tree vigor and sparse foliage. | Moderate |
| Grade Changes | Absence of a “root flare” at the base; tree looks like a pole in the ground. | High |
| Salt Injury | A sharp, distinct “halo” of brown along the very outer edge of the leaf. | Moderate |
| Anthracnose | Brown blotches that follow the leaf veins rather than starting at the edges. | Low |
| Verticillium Wilt | Dark, olive-green or brown staining in the sapwood under the bark. | High |
| Oak Wilt | Rapid “top-down” browning of the canopy (often in just a few weeks). | High |
| Dutch Elm Disease | Individual yellow or brown branches within a green canopy. | High |
| Bacterial Leaf Scorch | A yellow or reddish “band” separating dead margins from green centers. | Moderate |
| Emerald Ash Borer | D-shaped exit holes in bark and S-shaped larval galleries underneath. | High |
| Spider Mites | See if tiny crawling specks appear when branch is shaken over white paper. | Low |
| Girdling Roots | Flat side on the trunk at soil line; trunk appears “choked” with no flare. | High |
| 2-Lined Chestnut Borer | The gradual and progressive dieback of the crown from the top down. | High |
General Support for Your Trees
While specific treatments are needed to address some of the issues discussed above, simply providing good supportive tree care is all that is necessary — or in some cases, possible. So, while you’ll still want to contact a professional arborist anytime you see your tree leaves browning, the following steps will almost always prove beneficial.
- Provide supplemental water during dry periods. Supplying your trees with additional water helps offset the problems caused by droughts, winds, and high temperatures.
- Keep the rootzone covered with a layer of organic mulch. A 2- to 4-inch-thick layer of mulch will help protect your tree’s roots, improve soil structure, and retain moisture.
- Have your trees pruned regularly. By having a professional arborist prune your trees every two to five years, you can sometimes stop fungal and pest problems before they cause extensive damage.
- Conduct soil tests periodically and apply amendments as needed. While haphazard fertilizer application is usually just a waste of money, targeted treatments can address deficiencies.
- Protect your trees from physical and chemical harm. Wounds serve as an entry point for bacteria, fungi, and some insects, so do everything possible to protect your trees from these threats.
Treemendous Tree Care: Providing the Support You and Your Trees Need!
While you should never panic at the sight of brown leaves during the summer, it is important that you obtain professional assistance quickly. Some of the issues must be treated promptly to give your trees a good chance for a full recovery, while others may spread to the other trees on your property.
No matter the case, the professional arborists at Treemendous Tree Care are ready to help. We provide professional arborist services in Warren, Utica, Fraser, Roseville, and the rest of Southeast Michigan.
Contact us now to schedule a free onsite evaluation and learn the steps you’ll need to take to save your trees or limit the damage.
Sources & References
- Michigan State University Extension – “Two-lined Chestnut Borer”
This resource details the life cycle and management of a buprestid beetle that primarily attacks stressed oak trees, often leading to canopy dieback or tree mortality.
http://www.canr.msu.edu/resources/twolined_chestnut_borer - U.S. Forest Service – “Anthracnose of Eastern Hardwoods”
This federal technical bulletin describes the various fungal pathogens that cause leaf spots, blotches, and anthracnose cankers across a broad range of deciduous hardwood species.
https://www.fs.usda.gov/foresthealth/docs/fidls/FIDL-133-AnthracnoseHardwoods.pdf - State of Michigan – “Emerald Ash Borer (Agrilus planipennis)”
This official state invasive species profile outlines the identification, quarantine regulations, and environmental impact of the wood-boring beetle responsible for the widespread destruction of ash trees.
https://www.michigan.gov/invasives/id-report/prohibitedrestricted/emerald-ash-borer - Arboriculture & Urban Forestry – “The Effect of Tree Species and Size on Residential Property Value”
This peer-reviewed journal article presents quantitative research on how specific tree characteristics, including genus and physical maturity, correlate with market price premiums in residential real estate.
https://auf.isa-arbor.com/content/1/11/201
