Norway Maples losing bark on trunks and some branches and having some dead branches
I have two 15 year old Norway Maples. Both are losing bark & have branches dying from the top & south side. This has occurred for about 3 years or so.
One tree still has about 1 foot of growth on most branches but the bark has come off about half of the lower to mid trunk (equally on both sides, East & West) and on about 1/3 of the branches. About 10% of the branches mostly on the top middle & south have dried up & died (the recent snowstorm & freeze may have been a factor. On the other tree, half of the bark on the lower to mid trunk (all on the South side). The top 1/3 of the tree has or is losing branches and bark. It has about 6 inches of growth on most good branches.
What are the likely causes? A tree expert 2 years ago suspected root girdling and winter sun scald with the freeze of 3 years ago also a major factor. I am wrapping the trunks each winter now. We did have metal around both trunks from about 8 to 4 years ago to keep the squirrels off the branches but removed them. I do feed them spring and fall with ross root feeder pellets. The nursery said to trim off dead branches.
Douglas County Colorado trees and shrubs
It looks as if you do have some problems here with your Norway Maples. From what you have said, it appears that you are doing the right things. Peeling bark is environmental. Tree splits in bark can live for many years if damage area is narrow. Yours appears to be extensive. If your leaves are yellowing, wilting and dying branches, this could be a fungal disease called Hypoxylon Canker - no cure for this!
Decline in trees is evidenced by slow growth and branch die back. You said the trees are still growing, so I wouldn't give up just yet. Here is the name of an arborist in the Highlands Ranch area: Paul Goin with Tree Pros, Inc. at 303-791-3740. Good Luck and keep watching those maples.