I have a Eucalyptus Gunii which was planted 7 years ago. It has now grown
to a height of about 20 feet. Unfortunately, most of this growth is near to
the top of the tree, leaving the middle bare.

I would like to restore it to about 7 feet in the hope of making it "bush
out".

Any advice about the pros and cons of topping the tree and when is the
optimum time to do so would be very welcome.

Thanks in advance,

John