Clay and gumbo soils, warm night temperatures, and long growing seasons conspire to decompose any amount of organic matter a gardener works into the beds. Every garden bed in the Deep South that ever gets a topdressing of organic mulch should get it in fall. Perennials and shrubs particularly benefit from one inch of composted humus, leaf mold, or old gin trash applied now. Use a hand cultivator (that's the three-tined tool everybody has, but you don't know what to do with) to work in what’s left of the summer’s leaf mulch and aerate just a bit around plants before putting them to bed for the winter with a tidy mulch blanket. Take care not to cover perennial crowns completely so their clumps don’t stay wet all winter. For good looks and added insulation, add a layer of fresh pinestraw. Summer’s layer of pinestraw has gone limp yet stringy, and that stuff doesn’t work in well. Rake it out and chop before composting.