Winter cleanup of garden?

Perennials such as coreopsis and certain types of Rosemary can be trimmed back in Fall, but leave Lavender and roses alone until late winter. Thyme will care for itself, as will phlox, Johnson's geranium, etc.

Butterfly bushes may be trimmed in Fall or late winter/early Spring. Hydrangeas are trimmed according to their bloom time, so follow directions, carefully.

Dahlias, cannas, gladioli etc. must have bulbs lifted and overwintered in peat moss, and stored in a garage.

Clean up all leaf litter to reduce bug and slug infestations.

Depending upon your location, 4" of hardwood bark mulch should be more than sufficient. Pine needles are longer lasting and better for acid loving plants.

Some people place heavy black plastic on the ground surrounding perennials (but never near the base) to cook any weed seeds that may overwinter.