Answer: Trimming really depends upon the plant in question. The safest thing to do is to wait until the plants die down on their own and then remove the dead foliage. If the weather remains above freezing (I don't think you normally get frosty weather in Manhattan Beach), wait until December or January and cut everything down to ground level. As the weather turns more springlike, new stems and foliage will appear on your perennials.
Enjoy your garden!
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