LOL@ the idea that another tree could begin to get established in the greedy
root zone of a norway maple. I think the owner will have to bite the bullet
and take down the maple first, as painful as it will be to do without shade
for a few years. Red maples are fairly fast growing and don't have the bad
habits of either the Norway maple or silver maple, which grows VERY fast.
"Kay Lancaster" wrote in message
...
Looks like sunscald to me; common in thin barked trees exposed to sun
on the south or se sides. Sets the tree up for various and sundry
fungal diseases.

Acer platanoides, which is what I think you've got, is going to be a
big tree at maturity 40-50'x40-50' -- apparently much too big for where
you've got it, since someone has already pruned it drastically.

Personally, I'd start looking for specimens that fit the space available,
choose one and plant it to replace your norway maple, taking the maple
down
as soon as your other tree becomes more established. It's easier and
cheaper
sooner than later, and by choosing a species that fits the site size,
exposure
and soil type, you'll have a good chance of having a healthy, long-lived
tree
that adds value to your property.

http://www.extension.umn.edu/projects/yardandg
arden/diagnostics/mapleother-s.html

http://www.plantamnesty.org/pruning_tips_content.htm

Kay