I have a large (50-60 foot) birch tree on the southeast corner of my lot. It origionally had three trunks. I cut off the smallest (10" in diameter) last year as it grew out horizontally from the ground and was starting to block the dirveway.
Now I have a 16" trunk and a 24" trunk that start about two feet from the ground. The 16" trunk is growing over the house and blocking the sun. Can I trim it down to about 16 feet, leaving a 6" branch that grows on up to about 30 feet? Or would it be better to cut this trunk off entirely?
We have 80 mph winds on an annual basis, so I have to leave a tree that will stand up to hard blows or cut it down entirely. "Topping" isn't an option unless I want to be doing it every few years.:cool:

Topping is quite common, but a poor practice. What you are doing is much closer to the better practices. Cut the main trunk you are removing at an angle just past where the 6'' limb goes off. The 6'' limb leaving exceeds the minimum of 1/3 of what you cut off.

Making a 90 degree cut between branches leads to a witches broom of suckers which in a few years will be big enough to easily break off. That then leads to the very sort of wind damage you hope to avoid.