Now that we have had a few frosts and freezes, your landscape is probably mostly brown for the winter. Around this time of year I start go get a lot of questions about which plants should be cut back and which ones should be left. Fortunately for you, it's hard to go wrong on this. No plant will be hurt by not cutting it back, and most plants won't be bothered by being cut back. The decision-making mostly boils down to how much work you want to do now vs. in the spring, and what sort of look you like through the winter. To help you decide what goes and what stays, I'll break plants down into some helpful categories. As a general rule, most shrubs don't want to be cut down to the ground in the winter, so I won't talk about most of them. Instead we'll focus on perennials and shrubs that are exceptions to that guideline. Our groups will be floppers (perennials that don't hold up), upstanders (perennials that do hold up), stunners (perennials that keep their color), and shrubs with special instructions (I couldn't really come up with a good one-word label for them). Since I am a native plant nerd, I will stick with my habit of marking native species with an asterisk.
These are the plants that turn to mush when they freeze, collapse immediately in light snow, or just generally don't offer anything in the way of visual interest. There is no harm in leaving them until spring, but for a tidy appearance and an easier spring cleanup cut them back as they fade for the year (or even before then if you want to get your work in before it's freezing cold). Some of these have a clump of low-growing leaves at the ground that stay green later than the rest of the stalk or even all the way through the winter. I generally leave this basal foliage because it protects the crown of the plant through the winter, and because it's a pain to cut back a bunch of leaves that are only 2" tall to begin with.
- Bee Balm* (Monarda sp.)
- Bleeding Heart (Dicentra sp.)
- Bluestar* - leave it up until you get the amazing fall color! (Amsonia sp.)
- Columbine* (Aquilegia sp.)
- Tickseed* (Coreopsis sp.)
- Daylily (Hemerocallis sp.)
- Garden Peonies - do not cut back tree or Itoh peonies (Paeonia sp.)
- Garden Phlox* (Phlox paniculata)
- Hollyhock (Alcea sp.)
- Hosta (Hosta sp.)
- Lily-of-the-Valley (Convallaria majalis)
- Salvia (Salvia sp.)
- Shasta Daisy (Leucanthemum sp.)
- Solomon's Seal - another one with great fall color (Polygonatum sp.)
- Turtlehead* (Chelone sp.)
I love the look of dried seedheads and grasses left to sway and rattle in winter breezes. I know it's not for everyone, but if you are interested in keeping around some plants for their seeds and stems, this list is full of plants that add some subtle winter interest. Many of them are also native plant species that provide winter food and shelter for local wildlife.
- Aster* (Symphyotrichum sp.)
- Astilbe (Astilbe sp.)
- Black-eyed Susan* (Rudbeckia fulgida)
- Catmint (Nepeta x faassenii
- Echinacea* (Echinacea sp.)
- False Indigo* (Baptisia sp.)
- Fountain Grass (Pennisetum sp.)
- Goldenrod* (Solidago sp.)
- Japanese Forest Grass (Hakonechloa macra)
- Karl Foerster Grass (Calamagrostis x acutiflora 'Karl Foerster')
- Little Bluestem* (Schizachyrium scoparium)
- Maiden Grass (Miscanthus sinensis)
- Northern Sea Oats* (Chasmanthium latifolium)
- Beardtongue* (Penstemon sp.)
- Prairie Dropseed* (Sporobolus heterolepis)
- Prairie Dock* (Silphium terebinthinaceum)
- Russian Sage (Perovskia atriplicifolia)
- Sedum, tall varieties (Hyloptelephium sp.)
- Switchgrass* (Panicum virgatum)
When it comes to actual color in the winter landscape, there's more than spruce trees and boxwoods. All the plants on this list keep color through most of the winter, if not all. Most of them are green or silvery, but a few bring some brighter colors in. Coral Bells are especially great for this, because their leaves range from silver to purple to lime green to fire engine red.
- Ajuga (Ajuga reptans)
- Bishop's Hat (Epimedium sp.)
- Blue Fescue (Festuca glauca)
- Coral Bells* (Heuchera sp.)
- Christmas Fern* (Polystichum acrostichoides)
- Creeping Phlox (Phlox subulatum)
- Dianthus (Dianthus sp.)
- Hens-and-Chicks (Sempervivum sp.)
- Ice Dance Sedge (Carex morrowii 'Ice Dance')
- Lamb's Ear (Stachys byzantina)
- Lavender (Lavandula angustifolia)
- Lenten Rose (Helleborus sp.)
- Liriope (Liriope sp.)
- Pachysandra (Pachysandra sp.)
- Rosemary (Rosmarinus officinalis)
- Sedum, most low-growing varieties (Sedum species)
- Thyme (Thymus sp.)
- Yucca (Yucca sp.)
Shrubs with Special Instructions
Most shrubs can just be left alone for the winter. But some tend to die back and can be preemptively cut back, and others have different considerations. Shrubs that are marginally hardy in our area are the ones that tend to die to the ground anyway, and even if the branches make it through the winter you can often encourage better growth habits by cutting them to the ground in fall or early spring anyway. Plants that fall into this category for central Indiana include beautyberry, crape myrtle, and butterfly bush. That leaves hydrangeas and roses to talk about.
Hydrangeas aren't tricky, as long as you know what kind you have. All of them can be left as they are all winter without any harm to the plant. But two kinds are actually woody shrubs and should not be cut back. You can deadhead them if you want, but no cutting back. Those two kinds are oakleaf hydrangea and hardy or panicle hydrangea. Oakleaf hydrangeas are the easiest ones to pick out because, as their name implies, the massive leaves are shaped kind of like oak leaves instead of pointed ovals. Hardy or panicle hydrangeas are easiest to identify by their cone-shaped flower clusters. Both species have elongated flower clusters instead of dome-shaped ones. The other two types are mophead hydrangea (the kind that you can turn pink or blue) and smooth hydrangea (white flowers in big domes - 'Annabelle' and 'Incrediball' are popular ones). Both of these have domed or flat flower clusters, and both are made up of dozens of mostly un-branched stems growing directly out of the ground. These two kinds tend to die back to the ground over the winter, so if you don't like how the stems and old flowers look you can cut them back. It's best to wait until they have dropped all their leaves to prune them back, or they may waste energy trying to rush new growth that will be damaged when it freezes.
Roses strike fear into the hearts of many budding gardeners. We seem to get this idea that roses require a tremendous amount of work and attention, and that any simple mistake could kill them in an instant. It is true that some older heirloom varieties are very picky and are susceptible to all kinds of fungal diseases. However most of the roses that are easy to buy at the garden center today are pretty hardy and carefree (although, as we talked about a few weeks ago, rose rosette disease is on the rise). On all roses, pruning is much easier than you think. It's hard to go wrong as long as you frequently sterilize your tools to avoid spreading disease, and make your pruning cuts just above an outward facing bud. Timing is where there is the most room for error. If you do want to cut back roses in the fall, wait until it is consistently cold enough that the rose is going dormant. If you prune while you still have warm, sunny days, you can cause the rose to put out sensitive new growth which will then be damaged by frost.
Hopefully we've answered some of your questions and demystified the process of deciding what to cut back and what to leave. Ultimately, it's up to your preferences, and as long as you aren't cutting back shrubs while they're still green you won't hurt anything. Personally, I leave up as much as I can because I love how everything looks with frost and snow on it. But I know my approach probably drives some people up the wall. If you kind of want to leave your stuff up for the winter but don't want to feel lazy, consider joining me in taking the Lazy Gardener Pledge and justify your desire to curl up and hibernate by making your landscape a haven for wildlife in the winter. Want to curl up and hibernate, but can't stand the thought of a messy garden all winter long? Call us! Our leaf removal and fall cleanup season is in full swing, and we can add you to our schedule.