It depends on the type of bush. If it is a small, low-growing shrub or tree, you can trim it anytime after flowering and before seed production begins. The best time to do this is when the plant is dormant in winter (i.e., not growing). For pine trees, Christmas is probably your best bet since the cones will drop at that time anyway; for larch needles it’s mid-spring but I would advise against cutting them back anytime soon just to be safe because their weak growth period does not end until late summer/early fall.
So why bother with pruning cedars? Why not wait until they are dead? Because if you wait long enough they don’t die; instead they become so decayed that there isn’t much left of their base structure except for woody roots which turn into mushrooms which produce more resins every year! These mushrooms are already quite underground by late spring–they won’t hurt anyone who steps barefoot through an area where one has grown. It also makes sense ecologically to keep dead plants around as habitat for wildlife rather than having no plants whatsoever because then all sorts of other non-native species may take over your garden or yard including insects and rodents which could become pests later on should the animal population get out of control due to lack of predators being present in gardens/yards causing problems such as biting off chicks etc…but these animals will have nowhere else