Question
i have a 20 year old Chinese pistache tree in my backyard.  there are three bottom branches that are large and thick.  often we have to duck when this tree is blooming because these branches have low forming branches themselves that extend in many different directions.  i would like to know if it is okay to cut these bottom three large branches off to enable us to walk comfortably around this tree again.  of course we would follow the steps for trimming but want to know if limbs this size at this time in their life are okay to cut off.  thanks for your help.

Answer
Yes you can prune the lower limbs off without any problem to the tree. Prune the dead branch off about 1/4 inch from the trunk. This will leave a branch collar and the wound will heal over by itself. If the wound is more than 6 inches across after the cut I would paint the area with a wound dressing. This will keep water from getting into the wound. On wound less than 6 inches across I would leave natural and not paint.

On large trees it is best to make the first cut about a foot from the trunk on the under side then cut the branch off from the top leaving a stub about a foot long. Then you can prune off the stub and the heavy limb will not split the bark on the trunk.
Here is a web link to how to prune trees with a drawing of the large limb pruning method.
http://www.ces.ncsu.edu/depts/hort/consumer/factsheets/trees-new/text/pruning.ht.