· by Michael Blair, Nashville's Landscapers
Fall cleanup in Nashville tends to mean one thing: cut it all down, bag it, mulch it, done. A landscape treated that way looks neat in November and pays for it in spring, when the hydrangeas do not bloom, the lavender has rotted at the crown and the beds that were bare all winter have eroded into the lawn. The better approach is to sort the yard into what benefits from cutting now, what needs to wait, and what should stand until spring.
Cut back now
Anything diseased goes first, regardless of the rule for that plant. Peony foliage with botrytis, bee balm and phlox with powdery mildew, iris leaves showing borer damage, roses with black spot: cut, bag and remove from the property rather than composting, or the spores overwinter and return.
Hostas and daylilies collapse into mush after the first hard frost and can be cut then. Spent annuals come out. Perennials that self-seed aggressively, such as garlic chives and some coneflower varieties, are cut before the seed drops if you do not want a hundred more of them.
Leave until late winter
Ornamental grasses, coneflowers, black-eyed Susans, sedum and most of the native prairie perennials stand well through winter. The seed heads feed finches and the stems shelter overwintering insects, and the dead top growth protects the crown from the freeze-thaw cycling that Middle Tennessee winters specialize in. Cut them to a few inches in late February, before new growth starts.
Woody-based perennials and subshrubs are the ones most often killed by a fall haircut. Lavender, Russian sage, butterfly bush, caryopteris and rosemary should not be cut hard in fall; the cut ends take in water, the crown stays wet through our winter rain, and the plant rots. Prune them in spring once you can see where the new growth is coming from.
Shrubs: know which wood it flowers on
This is where fall pruning does the most damage. Shrubs that bloom in spring, including bigleaf and oakleaf hydrangeas, azaleas, forsythia, lilac, viburnum and most spireas, have already set next year’s flower buds on this year’s growth. Cut them in fall and you have cut off the flowers. They are pruned right after they bloom, not now.
Panicle and smooth hydrangeas, roses, crape myrtles and summer-blooming spireas flower on new growth and can be cut in late winter. Even then, crape myrtle should be thinned rather than topped. If you are not sure which hydrangea you have, leave it alone this fall and watch where it blooms next year.
- Spring bloomers: prune after flowering, never in fall
- Summer bloomers on new wood: prune in late winter
- Broadleaf evergreens: shape lightly in spring, not before a freeze
- Deadwood: any time it is obvious
Leaves, mulch and the beds themselves
Leaves that fall into beds can mostly stay, shredded or not, as a winter mulch that breaks down into the soil. Thick mats of large leaves such as sycamore or magnolia should be broken up so they do not smother crowns. Fall is also the better time to top up mulch here, because it holds moisture and moderates the freeze-thaw that heaves shallow-rooted plants out of clay.
Bare beds are the real risk on a sloped Nashville lot. A bed cleared to bare soil in October takes the winter rain directly, and by March the clay is crusted and the mulch has washed onto the walk. Leave the plant cover, keep the mulch in place, and do the heavy cutting in one pass at the end of winter.