Tree problems · Disease
Heart rot and wood decay: signs and what to do
Heart rot and wood decay is a tree disease, often seen on silver maple, red maple, northern red oak. Look for: conks, brackets or mushrooms growing on the trunk or large limbs.
General information, not a diagnosis. A certified arborist or your county extension office can confirm.
- Disease
- Silver maple
- Red maple
- Northern red oak
- White oak
- Sweetgum
- Tulip poplar
Signs to look for
Tick what you see. More ticks make it more likely, but only an on-site look can confirm.
0 of 6 signs ticked. Ticks stay in this browser only.
Season
Decay goes on all year inside the tree. Fruiting bodies such as conks and mushrooms often show in late summer and fall, and they can last for years.
How it spreads
Decay fungi enter through wounds, such as broken branches, bad pruning cuts, storm damage, mower and construction injuries, or dead roots. Spores spread by air to fresh wounds.
Where it is found
Wood-decay fungi occur in every state, and different fungi attack different trees. Check your state official map; ranges change.
Official sources
What to do
- 1
Do not guess. A conk shows decay is present, but not how much wood is left. Have an arborist assess the tree.
- 2
Keep people and cars away from a tree with large cavities, big conks or leaning while you wait for an assessment.
- 3
Do not fill cavities with concrete or foam. This is out of date and does not add strength.
- 4
Remove dead limbs and prune with clean cuts just outside the branch collar so wounds close over well.
- 5
If the tree is near a target such as a house, car or sidewalk and has major decay, removal or reduction may be the safest choice.
Safety first: do not climb, do not cut near power lines and do not use a chainsaw on storm-loaded wood. Call the utility for downed lines and 911 if anyone is in danger.
Prevention
Avoid wounding trunks and roots. Use proper pruning cuts, never top trees, protect roots during construction, and keep trees healthy with water and mulch. Fewer large wounds means fewer places for decay to start.
When to call a pro
Call a certified arborist if you see conks, hollows, cracks or a lean, especially on a large tree near buildings or people. A risk assessment can include tools to check how much sound wood is left.
Not sure who to call? Read how to hire a tree service or check is my tree dangerous?
Trees it affects
Usually seen on: Silver maple, Red maple, Northern red oak, White oak, Sweetgum, Tulip poplar, Eastern cottonwood, Weeping willow.
- Silver Maple
- Red Maple
- Northern Red Oak
- White Oak
- Sweetgum
- Tulip Poplar
- Eastern cottonwood
- Weeping Willow
See all species in our tree library, or pick a tougher tree with the tree picker.
For tree companies
How to explain heart rot and wood decay to a customer
Explain that decay is a risk question, not a yes or no on removal. Many hollow trees stand for decades; others fail. Show the signs, state what you can and can not see, and offer an assessment or a second opinion. Do not use fear to sell a removal.
Send this page to the customer after your visit so they can read the signs in plain words. See also selling plant health care and the job photo checklist.
Questions
Does a mushroom on my tree mean it must come down?
Not always. It does show decay is present, so it should be checked. How much it matters depends on the tree, the amount of sound wood and what is under it.
Can a hollow tree still be safe?
Sometimes. A tree can stay strong with a hollow if enough sound wood remains around it. A professional assessment helps decide.
Should I fill a hollow with cement?
No. This old practice is not recommended. It does not strengthen the tree and can cause more harm.
How does decay start?
Usually through a wound, such as a torn branch, a bad cut, storm breakage or damage from equipment. The fungi grow into the wood from there.
Can I stop decay once it starts?
No product reverses it. Trees can wall off decay to a degree. Good care and proper pruning help, and risk can be managed by pruning, support or removal.
How do I know if my tree is dangerous?
Look for conks, hollows, cracks, leaning and dead limbs, then get an assessment from a certified arborist. If danger is close, keep away and call 911 in an emergency.
Can Lirevon diagnose heart rot and wood decay on my tree?
No. Lirevon is a remote marketing team for tree service companies and does not do tree work. This page is general information, not a diagnosis. A certified arborist or your county extension office can confirm what is wrong with your tree.
How do I find a good local pro for this?
Search Google Maps for certified arborists or tree services near you, read their reviews and ask for proof of insurance. Get two or three written quotes. Our guide on how to hire a tree service lists the questions to ask.
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