Decay on a hybrid chestnut tree - Ask Extension
Good morning.
Can you identify this area of dead bark or decay that I see at the base of one of my hybrid chestnut trees. The tree is about 10 years ...
Knowledgebase
Decay on a hybrid chestnut tree #941700
Asked August 06, 2026, 11:01 AM EDT
Good morning.
Can you identify this area of dead bark or decay that I see at the base of one of my hybrid chestnut trees. The tree is about 10 years old. If you can identify it, can you tell me what to do about it?
Frederick County Maryland
Expert Response
This does not appear to be wood decay (it doesn't have the right features for common decay fungi), although it is hard to identify as to which fungus it may be. For now, just monitor the tree for any new symptoms or a notable change in the fungal growth, and feel free to share more photos in that event.
Of greater concern in the meantime is the presence of what looks like landscape fabric near the trunk base. Is this just a scrap of material, or is landscape fabric laid around the tree? In either case (and especially if it's not just a small fragment), it should be removed as soon as possible, since the longer it stays in place, the greater a risk it poses to tree health. Usually, grass doesn't grow well on top of landscape fabric, so we're not sure what we're looking at in terms of how extensive it might be. If the material has become tangled in the tree's roots, it might be impossible to remove, but should still be taken out as thoroughly as is feasible.
When trees are surrounded by lawn, the base of the trunk should be separated from the grass by a zone of mulch (or perennial plantings that don't need mowing). Having grass grow right up to the trunk base risks damage to the bark from mowers and string trimmers, the injuries of which can be fatal for a tree if they get colonized by an infection, wood-boring insect, or decay. Additionally, turfgrass eventually declines as it's shaded-out by the tree (so the area would need mulching or replanting at some point anyway), although before that point, the grass roots are competing with the tree's roots for moisture and nutrients. We recommend that the lawn be removed in a circle at least 2 or 3 feet out from the trunk in all directions, which can then be covered with 2 to 3 inches of mulch. If you prefer to keep the turf for now, make sure no herbicide used for weeds is applied near the tree, and that the bark is not touched by lawn equipment.
Miri
Of greater concern in the meantime is the presence of what looks like landscape fabric near the trunk base. Is this just a scrap of material, or is landscape fabric laid around the tree? In either case (and especially if it's not just a small fragment), it should be removed as soon as possible, since the longer it stays in place, the greater a risk it poses to tree health. Usually, grass doesn't grow well on top of landscape fabric, so we're not sure what we're looking at in terms of how extensive it might be. If the material has become tangled in the tree's roots, it might be impossible to remove, but should still be taken out as thoroughly as is feasible.
When trees are surrounded by lawn, the base of the trunk should be separated from the grass by a zone of mulch (or perennial plantings that don't need mowing). Having grass grow right up to the trunk base risks damage to the bark from mowers and string trimmers, the injuries of which can be fatal for a tree if they get colonized by an infection, wood-boring insect, or decay. Additionally, turfgrass eventually declines as it's shaded-out by the tree (so the area would need mulching or replanting at some point anyway), although before that point, the grass roots are competing with the tree's roots for moisture and nutrients. We recommend that the lawn be removed in a circle at least 2 or 3 feet out from the trunk in all directions, which can then be covered with 2 to 3 inches of mulch. If you prefer to keep the turf for now, make sure no herbicide used for weeds is applied near the tree, and that the bark is not touched by lawn equipment.
Miri
Thank you for the information and the instructions regarding fabric and mulch. Should I grub out the grass before placing mulch or just bury it under the mulch? Mulch type? Hardwood bark? Wood chips?
Michael
Using a shovel to strip the sod off is usually the easiest way, but any manual means that doesn't injure the tree's trunk base or any surface roots should be fine. While you could bury it to smother it, that volume of mulch would be too much to put over the tree's root flare and roots. The type of mulch is up to you, as long as it's biodegradable; wood chips, shredded bark, pine bark nuggets, or pine needles are all fine.
Miri
Miri
Thank you.
Michael
You're welcome.
