Tree Troubleshooting: What's Wrong With My Tree?

A symptom-by-symptom guide to figuring out what's going on before you call an arborist

How to Use This Guide

Trees can't tell you what's wrong. They show you. The trick is knowing which symptoms are emergencies, which are cosmetic, and which ones you can safely ignore.

This guide is organized by what you see. Find the symptom, read the likely cause, and decide whether you need professional help or can handle it yourself. When in doubt, call an ISA-certified arborist. A diagnostic visit typically costs $150-400 and can save you from either panicking over nothing or ignoring something serious.

Trunk Problems

Flat-sided trunk at the base (one side is compressed, not round): Likely cause: encircling or girdling root. A root is growing around the trunk, compressing it and restricting water flow. Excavate around the base with a hand trowel to find the offending root. If caught early (root is smaller than 1/3 the trunk diameter), an arborist can cut it. If the root is large relative to the trunk, the damage may be irreversible.

Bark damage near the ground (scrapes, gouges, missing bark): Likely cause: lawn mower or string trimmer damage. This is one of the most common preventable injuries to suburban trees. The fix is a mulch ring around the tree that keeps mowing equipment away from the trunk. Existing wounds should be left alone. Do not apply wound paint. The tree will compartmentalize the damage on its own.

Liquid oozing from the trunk: Likely cause: slime flux or wetwood. This is a bacterial infection that causes fermented, foul-smelling liquid to seep from wounds or cracks. It looks alarming but is usually not a health threat to the tree. Don't drill holes to "drain" it (an outdated practice). The tree is managing it.

Mushrooms or shelf fungus growing from the trunk: This is the one that should worry you. Visible fungal fruiting bodies on the trunk indicate extensive internal decay. The mushroom is the reproductive structure. The organism itself is deep inside the wood, breaking down structural tissue. Get a professional assessment with a resistograph. The tree may look fine from outside but be structurally compromised.

Branch Problems

Dead branches in the crown (no leaves, bark falling off): Common and expected in mature trees. Up to 10% deadwood in the crown is normal. Remove dead branches over walkways, driveways, or structures. A dead branch 6 inches in diameter can weigh hundreds of pounds. Schedule crown cleaning every 3-5 years.

Bright yellow leaves on one or two branches while the rest of the tree is green: Likely cause on elms: Dutch elm disease. Call an arborist immediately. On oaks: possible oak wilt. On other species: could be a localized vascular blockage from a branch injury or girdling.

Webs in branches or covering branch tips: Fall webworm or Eastern tent caterpillar. These look alarming but rarely threaten tree health. The tree will recover its leaves. You can prune out web-covered branches if you want, or just wait. Natural predators usually control the population the following year. Spraying insecticide kills the predators too, often making the problem worse the next season.

Many branch tips snipped off and on the ground: Squirrel damage. Annoying but not a health concern. Squirrels prune small branch tips, especially in spring and fall. No treatment needed.

Black clumps on cherry tree branches: Black knot disease. The black, hard, swollen growths on branches are a fungal infection. Prune infected branches 6-8 inches below the visible knot during dry weather. Sterilize your tools between cuts. If left untreated, it spreads throughout the tree.

Leaf Problems

Leaves sticky with black coating: The sticky substance is honeydew (excretion from aphids, scale insects, or other sap-feeding insects). The black coating is sooty mold, a fungus that grows on the honeydew. It looks terrible but doesn't directly harm the tree. Hosing leaves down with water knocks off both the insects and the mold. Chemical treatment is rarely necessary because ladybugs and other predators usually control the aphid population naturally.

Leaves wilting or drooping: Check soil moisture first. Push a screwdriver into the soil 6 inches from the trunk. If it slides in easily, the soil is moist and wilting may indicate root damage, disease, or transplant shock. If the soil is dry and hard, the tree needs water.

Leaf edges turning brown and crispy (leaf scorch): Usually drought stress. The tree can't supply enough water to the leaf edges, so they die first. Deep watering is the fix. In some cases, leaf scorch can indicate bacterial leaf scorch (a serious disease in oaks and elms) if it appears in the same pattern year after year and progressively worsens. Have an arborist check if the pattern is consistent.

Small leaves, sparse canopy, reduced growth: Multiple possible causes: root damage from construction, soil compaction, drought, nutrient deficiency, or root rot. This is a tree in decline. The canopy is thinning because the root system can no longer support full growth. Diagnosis requires a professional assessment of both the crown and the root zone.

Holes in leaves: Usually insect feeding (leaf beetles, caterpillars, sawflies). Minor leaf feeding is cosmetic and doesn't threaten tree health. A healthy tree can lose up to 25% of its leaf area and fully recover. Don't spray insecticide unless an arborist confirms a serious infestation.

Yellow or whitish leaves with green veins (interveinal chlorosis): Iron deficiency, most common in alkaline soils. The tree can't absorb iron from high-pH soil. Common in species like red maple, pin oak, and sweet gum planted in areas with naturally alkaline or limestone-derived soil. Chelated iron treatments provide temporary relief. Long-term, the tree may be the wrong species for your soil type.

Root Zone Problems

Soil heaving or cracking on one side of the tree: Potential root plate failure. The tree may be starting to uproot. This is an emergency if the tree is near a structure. Keep people away and call an arborist immediately.

Roots lifting sidewalks or driveways: Structural roots are growing laterally (as they should) and pushing up pavement. Options: root pruning on one side (risky for tree stability), ramping the sidewalk over the roots, or replacing the pavement with a permeable material. Do not cut roots on both sides of the tree or cut roots larger than 2 inches in diameter without an arborist's assessment.

Mushrooms growing in a ring around the base: Armillaria root rot (honey fungus). This is a serious root disease that can kill trees. The mushrooms appear in fall around the base, often in a ring pattern. There's no chemical treatment. An arborist can assess whether the remaining root system is sufficient to support the tree. If the tree is in an area where failure could cause damage, removal is often the safest option.

When to Worry vs When to Wait

Call an arborist today (emergency): Sudden lean that wasn't there before. Soil cracking at the base. Large branches hanging but still attached ("hangers"). Any tree or branch touching or near a power line. Visible trunk cracks that opened during a storm.

Call an arborist this week: Mushrooms on the trunk or at the base. Progressive crown dieback over multiple seasons. Codominant stems with visible included bark on a tree near a structure. A tree that was damaged during recent construction.

Schedule within a month: Dead branches over walkways or driveways. Trees not pruned in 5+ years. New pest or disease symptoms you can't identify.

Don't worry about it: Minor leaf feeding (holes in leaves). Fall webworm or tent caterpillars. Slime flux. Lichen or moss on bark (it's not parasitic). Leaf drop in fall (obviously). A few dead twigs at branch tips (normal dieback). Squirrel pruning.