Hollow in oak tree - Ask Extension
Our 80 plus year old oak tree splits into two main shoots about 8 feet up. At the split there is a hollow. Tree trimmer mentioned it has water in it. ...
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Hollow in oak tree #925458
Asked March 05, 2026, 9:31 AM EST
Our 80 plus year old oak tree splits into two main shoots about 8 feet up. At the split there is a hollow. Tree trimmer mentioned it has water in it. With freeze/thaw and expansion, do we need to do anything about this? They mentioned we could drill a 5/8 inch hole to keep it drained, but curious if that is the correct option?
Crow Wing County Minnesota
Expert Response
Do not allow a drainage hole to be drilled. It will create an opening for pathogens to infect the tree. The following articles discuss this and the potential danger of trees with dual leaders. The two shoots or "leaders" may break apart and separate in a wind storm.
Check with a ISA Certified arborist as to the best prevention methods for keeping the tree.
https://www.treesaregood.org/findanarborist
https://extension.psu.edu/programs/master-gardener/counties/montgomery/the-learning-gardens/pruning-trees-a-case-study
https://hort.ifas.ufl.edu/woody/cavity.shtml
https://ask.extension.org/kb/faq.php?id=781702
https://hnr.k-state.edu/extension/horticulture-resource-center/common-pest-problems/documents/Tree%20Cavities.pdf
Check with a ISA Certified arborist as to the best prevention methods for keeping the tree.
https://www.treesaregood.org/findanarborist
https://extension.psu.edu/programs/master-gardener/counties/montgomery/the-learning-gardens/pruning-trees-a-case-study
https://hort.ifas.ufl.edu/woody/cavity.shtml
https://ask.extension.org/kb/faq.php?id=781702
https://hnr.k-state.edu/extension/horticulture-resource-center/common-pest-problems/documents/Tree%20Cavities.pdf
