What’s your strategy for fall garden clean up?  Are you a Clean-Sweeper, removing every fallen leaf, cutting back every perennial, mulching all the beds and trimming all the evergreens?  Or do you subscribe to the Let it Be theory, simply allowing nature to take its course, leaves falling where they may and plants fending for themselves? 
I’d like to suggest that neither of those approaches may be wise.  While some believe leaving any dead plant standing is a sure way to incur the ire of the entire community, treating your garden so severely might do more harm than good.  And turning a blind eye to that 6-inch pile of wet, matted leaves on your lawn and beds could be asking for trouble.
It’s understandable that unless one knows exactly what different plants need, an all or nothing approach simplifies the task.  But with a little knowledge, you can easily do what’s best for your garden, and the environment, in the long run.
So, let’s learn to leave the Clean Sweeping and Letting It Be behind, and become Nature Nurturers—making decisions based on what’s best for the plants and wildlife.  Here are some general tips and plant specifics to start you on your way.

  • Mulching should be done after the first hard freeze.  This will minimize frost heave caused by alternating freezing and thawing.  You want the ground to be frozen and perennials dormant before you mulch. 
  • There should only be up to a 3-inch layer at any one time.  If you put down a 3-inch layer in spring, you probably only need to add another inch—only replace what has decomposed.
  • Keep mulch 1 inch away from crowns of plants and trunks of trees—otherwise this is an invitation for disease and insects.  Even though you see it piled up against trees everywhere, IT’S WRONG!!  If you can’t see a tree’s “root flare” (like the bell-bottom on pants), it’s mulched too deeply.  This was invented by landscapers to charge more for (unneeded) products and services—don’t let them get you.  Same for putting down a thicker layer of mulch in beds than necessary.  If they don’t know how to mulch properly, show them or fire them.
  • Hybrid tea roses may be mulched 2-3 inches over the crown—this should be removed as new growth emerges in spring 

Leaf Clean-up:

  • Many eco-websites and social media are telling you it’s fine to let the leaves alone.  And yes, of course, that IS natural and healthy in woodland areas where trees already exist.  Your lawn and garden have much different requirements.
  • Leaves should be shredded if they are to be left in situ—you can do this with a lawnmower.  Running the mower over them regularly should do it, but don’t wait until there’s so many you can’t see the ground between them. Wet whole leaves will mat down, especially with snow cover—you may as well cover your lawn with layers of wet newspaper.
  • Shredded leaves are a fine mulch for your perennial beds.
  • Unshredded leaves are great to cover your empty vegetable garden or beds as they will help to keep weeds out.
  • Don’t use leaves (or mulch heavily) where you have plants you want to re-seed—it may prevent germination.
  • Remove any fallen leaves on or under plants that had disease issues and dispose of in the TRASH—do not compost.  Without this removal, spring rain and wind will spread the problem even faster.  Particularly susceptible plants: lilac, hydrangea, dogwood shrubs, crape myrtle, some viburnum, roses. 

Fall Pruning: 

  • In general, NO!  Dead, broken, or diseased stems & branches are the exception—remove as soon as possible as they occur.
  • Late pruning will encourage tender new growth that is likely to be injured by freezing temperatures.  Try to complete pruning of any woody shrubs at least 2 months before average first frost date for your area.
  • Absolutely do not fall-prune early spring bloomers like azaleas—they have already formed their buds and you will be removing them.
  • If you truly must cut something back at this time, leave as much top growth as possible to protect the plant.  You can then do your final pruning and shaping after the plant is dormant in winter, or before the first flush of growth in spring. 

Reasons to Cut Back Perennials:Cut bee balm back in fall if powdery mildew is present

  • Decreases the incidence of disease and pest infestation in susceptible plants (especially ones that are already affected)
  • Reduces garden chores in spring
  • For plants with no winter interest, garden looks tidier 

Reasons NOT to Cut Back Perennials in fall:

  • Dead foliage protects crowns, especially tender plants
  • Removes seeds for birds
  • Removes habitat for beneficial insects
  • Many plants have winter interest, especially with snow cover
  • Leaving a few inches of old stems can help mark the spot for perennials that emerge late in spring (Butterfly weed, Balloon flower, Hardy hibiscus)
  • Landscape services often don’t know the difference between your plants and weeds in the spring.  Remaining foliage can be a clue that it’s a desirable plant—otherwise they would have weeded it in the fall, right?  

Cut Back to 1”:

  • Bee Balm (Monarda):  if powdery mildew is presentgoldfinch perched on thistle seedheads
  • Brunnera:  no winter interest
  • Daylily:  over accumulation of old foliage weakens the plant
  • Hosta:  turns slimy over winter; harbors slugs
  • German Iris:  leave a 2” fan of foliage—prevents borers (never mulch over rhizomes); divide by early fall
  • Peony:  to prevent foliar and flower disease (mulching too heavily will prevent blooming); divide by early fall
  • Tall Garden Phlox:  if powdery mildew is present (no winter interest)
  • Pulmonaria:  if mildewed
  • Veronica:  no winter interest

Leave new fall basal foliage, but you can cut old stems:

  • Asters
  • Meadow Sage (Salvia 'May Night' and similar)
  • Penstemon
  • Pincushion flower (Scabiosa)
  • Shasta Daisy (Leucanthemum)
  • Yarrow (Achillea)

Do not cut back in fall and why:  

  • Agastache:  protects crownMarigold seeds may be harvested in fall
  • Annuals such as cleome, cosmos, marigold, zinnia: if you want them to re-seed (or first harvest the seed heads once mature)
  • Avens (Geum): (semi-)evergreen foliage
  • Baptisia: interesting seed heads
  • Bergenia: evergreen foliage
  • Black-Eyed Susan (Rudbeckia): seeds for birds
  • Bugleweed (Ajuga): evergreen foliage
  • Chrysanthemum: protects crown
  • Coneflower (Echinacea): seeds for birds
  • Coreopsis: seeds for birds
  • Coral Bells (Heuchera): evergreen foliage--tidy in spring
  • Dianthus: evergreen foliageEpimedium is an evergreen groundcover for shade
  • Epimedium: evergreen foliage--tidy in spring
  • Ferns: Autumn, Christmas, Holly, Tassel and other evergreen ferns: tidy in spring
  • Hardy geraniums: (semi-)evergreen foliage--sprawling ones can be cut back after first bloom as needed
  • Hardy hibiscus:  overwintering/nesting site for pollinators
  • Hellebores: evergreen foliage--tidy in spring
  • Herbs: with (semi-)evergreen foliage: thyme, oregano, sage, burnet, tarragon, rosemary--can be cut back by 1/3 to 1/2 in spring
  • Gayfeather (Liatris): seeds for birds
  • Hens and Chicks (Sempervivum): evergreen--remove browned leaves 
  • Lamium: (semi-)evergreen foliage (unless disease is present)
  • Lavender: evergreen foliage--yearly spring pruning  will keep it from getting woody: never cut back into old wood!
  • Montauk daisy: protects crown
  • Ornamental Grasses: winter interest, seeds/protection/nesting material for birds, overwintering site for pollinators and beneficial insects
  • Oxeye Sunflower (Heliopsis): seeds for birds
  • Moss Phlox: evergreen foliage--tidy after bloom in spring
  • Oriental Poppies: plants have come out of summer dormancy--fall foliage is new; divide by early fall
  • Red hot poker (Kniphofia): protects crown
  • Sea Holly (Eryngium): interesting seed heads
  • Sedum: upright varieties have good winter interest; many low-growing types are evergreen

Click here for more fall garden cleanup tips!