Answer: As a general rule, trim out the dead portions if they are truly dead. Dead wood can be removed at any time. To check for live wood, begin at the tip of the branch and work your way down it. Live wood is somewhat flexible and has green inside the bark. Dead wood will be off color gray or brown, and it is dry and brittle and snaps in your hand.
You can also try to open up the plant to light and air by selectively removing entire branches, reaching deep inside the bush to cut. The best time to prune is really in the winter. Here are some additional pointers: (YOu may need to cut and paste the complete url into your browser to make it work correctly.)
Thinning with illustrations
There are also pest/disease issues that can cause dead branches. The first article above includes links to some information about that. I hope this helps you renew your shrubs!
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