Trimming a River Birch - Ask Extension
Is there a maximum width of a limb that can be safely trimmed? I've heard that 10" is maximum but also heard that if once trimmed, paint can be appl...
Knowledgebase
Trimming a River Birch #771345
Asked September 13, 2021, 12:07 PM EDT
Is there a maximum width of a limb that can be safely trimmed? I've heard that 10" is maximum but also heard that if once trimmed, paint can be applied to cut area to limit disease etc.
Dakota County Minnesota
Expert Response
Hello Mark, happy to help.
We in the tree advisory position have a couple of rules of thumb when it comes to pruning trees.
First, we evaluate the tree canopy of leaves and take no more than 25% of the live canopy per year which means dead branches don't count. Second, when taking a branch, especially one attached to the main trunk, it should be no more than one third the diameter of the trunk. If it is larger, we trim some of the outer branches on that limb and wait for the trunk to get large enough so that the intended limb becomes one third the diameter. That could take a few years so we trim the ends of the branch each year until that happens. Trimming the ends of the branch sends a chemical message to the tree to put growing energy elsewhere in the tree and not along that branch. That's why it takes some time.
As for painting the cut. We do not recommend that. Trees have the natural ability to heal over the cut if it's correctly done. Here is a link to pruning trees where you'll find how the cut is made against but into the branch collar. If you paint the cut, the tree may be hindered from healing and that could introduce the possibility of disease or fungal infections.
If you find that this is getting too much for a DIY or this looks to be such a large tree that it could pose a danger without the right equipment, here is a link to information about how to find and hire a certified arborist.
Good-luck!
We in the tree advisory position have a couple of rules of thumb when it comes to pruning trees.
First, we evaluate the tree canopy of leaves and take no more than 25% of the live canopy per year which means dead branches don't count. Second, when taking a branch, especially one attached to the main trunk, it should be no more than one third the diameter of the trunk. If it is larger, we trim some of the outer branches on that limb and wait for the trunk to get large enough so that the intended limb becomes one third the diameter. That could take a few years so we trim the ends of the branch each year until that happens. Trimming the ends of the branch sends a chemical message to the tree to put growing energy elsewhere in the tree and not along that branch. That's why it takes some time.
As for painting the cut. We do not recommend that. Trees have the natural ability to heal over the cut if it's correctly done. Here is a link to pruning trees where you'll find how the cut is made against but into the branch collar. If you paint the cut, the tree may be hindered from healing and that could introduce the possibility of disease or fungal infections.
If you find that this is getting too much for a DIY or this looks to be such a large tree that it could pose a danger without the right equipment, here is a link to information about how to find and hire a certified arborist.
Good-luck!
