Fall is here! It’s time to start putting the garden to bed before the frosty winter season begins. Here’s what I’ve learned over the years about how to winterize perennials.
There are five steps to winterize perennials:
- Step 1: Remove Slimy Dead Foliage and Fallen Leaves
- Step 2: Identify Plants for Winter Interest, Birds, and Beneficial Insects
- Step 3: Remove Foliage of Perennials That Provide Shelter to Garden Pests
- Step 4: Mulch Over Tender Perennials To Stabilize Soil Temperature
- Step 5: Store Exotic Perennials in a Sheltered Location
Read on to learn more about how to winterize perennials.
The basics of winterizing perennials
Winterizing perennials is a wonderful way to put the garden to rest in the fall after a busy growing season. It’s the perfect time to compost fall foliage, consider plants for winter interest, remove shelter for garden pests, and protect tender plants from the harsh conditions of wintertime. While each plant has different needs, there are a few main themes for winterizing perennials.
Many perennials (garden plants that come back every spring) are herbaceous, meaning that only the portion of the plant below ground lives through winter. Some will keep a few woody stems over winter, and others will keep a few young leaves at their base. Unlike shrubs, however, the majority of the plant above the ground grows back anew each spring. Winterizing perennial beds in the fall is an important factor in their overall health. A little maintenance in the autumn will help your perennials thrive during the next growing season.
So how do you prepare a perennial plant for winter? The answer depends on whether you’re leaving your garden to emulate nature or whether you’d prefer a tidier look.
A garden can of course be left to its own devices in the fall. Our meadows and forests winterize themselves without too much help from us! If, however, we want our garden to look well-kept, to discourage certain garden pests, and to grow plants that aren’t completely comfortable in our local environment, there will be some perennial winterizing work to be done. Your beds will be tidy and ready to get going in the spring.
The opposite of leaving your perennials alone in the fall is winterizing each plant separately and deliberately. Fortunately, not all plants need such dedicated attention in the fall. The hardiest perennial plants don’t need any extra attention and can be left to their own devices.
Some perennials, especially new plants and tender perennials, will benefit from some winterizing. They’ll be more likely to survive the cold winter season and come back again next spring. As gardens can have lots of different plants in them, one garden may have some perennials that are left for winter, some that are cut back, and some that are moved to a sheltered location.
The fall cleanup process begins with removing dead/dying/diseased foliage, which should be done throughout the year. September is a particularly appropriate time to take a look at your plants, clean up any struggling foliage, and make a plan for how to winterize perennials in the garden.
Late fall is the best time to winterize perennial plants. A hard frost can be the signal to prep the beds for winter. If below-freezing temperatures are forecasted overnight, or you wake up to frost on the ground, it’s likely a good idea to winterize your perennials within the next few weeks. If you miss this window, your perennials can still be winterized as long as they’re not buried in snow yet. If they are already covered in snow, take solace that the snow does insulate the perennials somewhat from the harshness of winter freeze/thaw cycles.
Let’s get going on learning how to winterize perennial plants!
Step 1: Remove dead foliage and fallen leaves
The first step to winterizing perennials is to remove slimy/diseased/otherwise gross dead foliage and fallen leaves. Cleaning up and removing dead/dying/diseased foliage should happen throughout the year, but there is always extra work in this category in the fall. This is especially true if you live in a location with lots of deciduous trees that lose their leaves in autumn. Get your pruners, rake, and wheelbarrow ready!
Always remove dead, dying, and diseased foliage from perennial plants as soon as it is noticed. Truly diseased foliage can be tossed in the fire pit, but most perennial plant debris can be composted to recycle it into lovely, rich plant food. Removing struggling branches and foliage is a year-round task. Don’t leave it all until fall (or worse…spring!).
Keeping the base of plants free from foliage debris is KEY. Cooler fall temperatures invite moisture, which can create a wet environment at the base of perennials if there is plant debris restricting airflow.
Gently rake up and remove fall leaves and other foliage from the base of each plant as it accumulates to let the autumn wind blow through the stems and keep the air fresh. This includes annuals that are at the end of their lifecycle and any weeds that have crept in, as well as the leaves left over after spring bulbs like tulips are done blooming. Foliage that has fallen directly into the middle of the plant may have to be pulled out by hand.
If left on the ground, large dead leaves create a moist decaying mat that makes a lovely blanket for pest insects to shelter for the winter or lay their eggs. Removing the leaves before they become a big wet blanket for bugs will make your garden less attractive to pests.
Moisture, in general, isn’t a bad thing…it’s just not great to create a long-lasting moist environment around the above-ground portion of the stems. Perennials should be watered throughout the fall until the ground freezes. The water requirements will likely be much lower than in the heat of summer, but the soil should not be left to dry out for an extended period in the fall.
So what to do with all of these fall leaves collected from the perennial beds? Fortunately, shredded fall leaves make a wonderful mulch for perennials (see step 4 below). Keep small or shredded leaves to use as a protective mulch to insulate perennial plants from temperature swings. Don’t actually mulch until after frosty temperatures arrive, but it’s very handy to get your shredded leaf mulch ready for when the time is right.
One last task before frost hits is to divide any perennial plants that require it. Early fall is a great time to divide perennials as they have a bit of a chance to root into the soil before going dormant. A few weeks of mild temperatures will allow the divisions to root in before winter.
Step 2: Identify perennials for winter interest, birds, and beneficial insects
Everything in the garden is balanced. While we generally remove most dead foliage to discourage pests, many gardeners enjoy leaving some perennials standing in the fall both for aesthetic reasons and for the beneficial creatures of the local ecosystem.
Step #2 of winterizing perennials is to identify which foliage will be left standing over the winter. Tall ornamental grasses and graceful seed heads provide striking winter interest, even amidst a snowy garden. Birds and other beneficial creatures will also appreciate the seeds left for them to enjoy during the bleak winter season.
So, should I cut back my perennials for winter? It depends on what kind of perennials you have in your garden and whether or not you value winter interest and providing habitat for beneficial. While removing dead/dying/diseased plant matter is important throughout the year, purposefully leaving select elements makes sense in many gardens. While the dead leaves of a perennial may be cleaned up in the fall, consider leaving the seed head standing for the wintertime.
Deciding not to prune down perennials is the least amount of work in the fall. There’s more work to be done in the spring of course, but there always seems to be more enthusiasm for yard work in the spring. The foliage also detaches from the plant more easily in the spring (and takes up less volume since it’s starting to decay already). There are sometimes benefits to putting things off!
Here are some perennials to consider leaving for winter interest and beneficial creature habitat:
- Bee Balm
- Black-Eyed Susan
- Cardinal Flower
- Coral Bells
- False Indigo
- Hens & Chicks
- Ornamental Grasses
- Russian Sage
- Sea Holly
These perennial plants either have striking tall forms, seeds for the birds, or foliage that can survive chilly winter temperatures. Including a few of these plants in your perennial beds will help them look great even in the wintertime.
“Never overtidy the garden. Don’t cut down all the perennials; leave seeds for the birds, and standing stems to catch the snow or make winter shadows.”Thrifty Gardening: From the Ground Up, by Marjorie Harris
“Some perennials, such as grasses, Chinese lantern (Physalis), cornflower (Centaurea), globe thistle (Echinops), golden rod (Solidago), honesty (Lunaria), Iris foetidissima, Michaelmas daisy (Aster), sedum, sunflower (Helianthus) and yarrow (Achillea), produce ornamental seedbeds or fruit. All or some of these can be kept in place to enhance the garden during autumn and winter.”Pruning & Training (Royal Horticultural Society), by Geoff Hodge
Step 3: Remove foliage of perennials that provide shelter to garden pests
Not all perennial plants are best left alone in the fall. Some are really best trimmed down before winter to minimize habitat for garden pests. Removing the foliage of certain perennials is step #3 of the perennial winterizing process.
Remove leaves and stems that are really struggling as soon as they become apparent, but it’s best to leave the majority of leaves on the plant until they die back naturally from frost or freezing temperatures. The leaves are how plants create their energy, and the plant should be allowed to store energy for winter for as long as possible. For foliage extinguished by freezing temperatures, waiting until the foliage dies naturally before trimming it off helps the plant be as prepared as possible to survive the winter and put on healthy growth in the spring. Resist the urge to cut down perennials before freezing temperatures.
Perennials naturally begin to die back to the ground after a hard frost or below-freezing temperatures. This is the perfect time to cut back stems. Perennials that are cut down in the fall are often plants that provide greater benefits to garden pests than beneficial creatures during the winter or plants that don’t provide much winter interest to the garden. I like to cut stems back about 6 inches from the ground surface.
Here are some perennials that are often cut back in the fall:
- Columbine (leave the young leaves around the base of the plant)
- Hardy Hibiscus
- Hollyhock (leave the young leaves around the base of the plant)
- Shasta Daisy
Cleaning up the foliage from these plants will leave a tidy garden for the winter and have you ready to get going in the spring. All the foliage (except diseased bits) can be composted along with shredded autumn leaves.
When to cut back perennials for winter
Perennials should be cut back for winter in late fall. Wait until the foliage has started to die back before attempting a hard pruning. Generally, this window of opportunity will come after a hard frost or hard freeze but before the garden is blanketed in snow.
In many temperate zones, October and November are ideal months for cutting back perennials before the winter. Perennial plants should be cut back after a freeze. By timing the fall pruning well, the plant will just be going into dormancy, and it won’t miss its dead foliage.
How to cut back perennials in the fall
Once frosty temperatures have hit, cut perennial stems back to about 6 inches from the ground surface. Any young leaves close to the base of the plant can be left to protect the plant over winter. The remaining 6” stems sticking out of the ground will be mulched in the next step of this process.
This method leaves a tidy garden in the fall while still leaving a bit of an indication of where plants are for the spring. There will be no wet, decaying foliage to pick up in the spring, but you’ll be able to see where to expect new growth to sprout up. If you don’t like to see stems sticking up, it’s fine to cut them off quite low to
“Cut back leaves and stems to 1 to 2 inches above the ground in the fall, generally after the first frost (and before a heavier snowfall causes them to collapse).”The Martha Manual: How to Do (Almost) Anything, by Martha Stewart
As with regular pruning, keep your tools clean and sanitized. Compost foliage unless it shows signs of disease.
Step 4: Mulch over tender perennials to keep the soil temperature stable
Step number four is to mulch over tender perennials to protect their roots and crowns from harsh winter conditions. Perennial plants can be harmed by repeated freeze/thaw cycles and by extreme cold or winds.
A bit of a cozy blanket on top of the roots is helpful to insulate the plant from the harshness of winter. While mulch does provide the warmth of a cozy blanket, the main benefit of mulch is to insulate the soil from rapid temperature swings. The mulch keeps the ground from repeated freezing and thawing, which is harmful to plant roots. Basically, mulch keeps the soil temperature steady by shielding it from the winter sun.
So, not only does a layer of mulch act as an insulating blanket for wintertime, it also helps keep the soil and the roots at a consistent temperature. Mulched roots are less likely to heat up in the sunshine of the day, just to freeze solid as the sun goes down. This swing in temperatures can be very hard on them. The mulch helps keep temperature changes slow and steady.
The stable soil temperature lessens the chances of frost heaving. Frost heaving is a mechanism in which freezing water “jacks up” the soil around a plant. This action can dislodge a plant from the surrounding soil and even expose the root crown directly to the air (and wind).
Frost heave is most likely to occur when soil repeatedly freezes and thaws. An unprotected plant could go through several freeze/thaw cycles in a single day if temperatures were hovering just below freezing and the location of the plant was such that it was in and out of the shade throughout the day. This is especially true if the freeze/thaw was occurring without snow cover. This would not be a great situation for the perennial!
While regular mulching is common in most gardens, this particular “winter-protection” type of mulching is specific to climates that experience freezing temperatures. This mulch is applied solely to protect the roots and crown of the plant from winter conditions. It is applied in addition to or in combination with the general landscape mulch used to suppress weeds and retain soil moisture.
The extra mulch also holds in moisture over the winter, setting the plant up for success in the spring. The insulating properties of the mulch patch extend into spring when a warm spell could pull a plant out of dormancy too soon. In this manner, the mulch makes the soil warm up very slowly, minimizing the chance of early sprouting (and late winter die-back).
Note that mulching is rarely required in areas where winter temperatures remain above 40-50 degrees Fahrenheit. Even in very cold zones, many perennials don’t need extra winter protection above the soil line. Some plants have evolved to withstand freeze/thaw cycles and extreme temperatures. In general, hardier perennials don’t need mulch. They are able to survive winter without a cozy blanket (so long as they get some moisture in the fall).
Snow cover can also be a great insulator, but its presence can’t always be depended upon. Because of the uncertainty involved (and the cost + effort to replace plants), mulching over perennials is a common practice for winter protection. Some gardeners just mulch over all their perennials, but most
When to mulch perennials in the fall
The best time to mulch perennials in the fall is after the first freeze or hard frost. This will be when you wake up in the morning to find the dahlias dead, and the annuals crisped over. This timing coincides nicely with the previous step of removing foliage after the cold has killed it. Wait until freezing temperatures arrive, trim down foliage, and then apply a layer of mulch on top of the roots. Any nutrients in the mulch won’t encourage the plant to grow because the plant should be dormant. Winterizing perennials is best done before the ground freezes solid.
Mulching perennials in the days after the first freeze stabilizes the temperature of the soil. The soil will stay near-freezing and gently freeze solid as winter progresses. Mulching right after freezing temperatures first arrive will help the roots of the plants avoid the freeze/thaw cycles that are particularly common in autumn. The layer of mulch will keep the soil temperature steady rather than allowing the sun to heat it right up during the day just to have the exposed soil freeze hard in the evening.
What to mulch perennials with for winter protection
The best mulches are loose, organic, insulating materials. It’s also nice if whatever you use isn’t too much work to clean up in the spring. Choose something that will be easy to work with in both the fall and the spring.
My favorite mulch is homemade compost. Shredded deciduous leaves are a close second. Both can be raked into garden soil in the spring instead of requiring wheelbarrow transportation to the compost heap. The nutrients from the compost and shredded leaves slowly become available to the plants in the soil (hopefully just in time for spring!).
That being said, there are lots of organic materials that make great insulating mulches. These loose materials allow a bit of air movement instead of matting down and smothering the plant. They’re also not likely to introduce many new problems, such as weed seeds or disease.
Here are some ideas for materials to use as winter mulch:
- Homemade Compost
- Shredded Deciduous Leaves
- Evergreen Boughs
- Pine Needles
- Wood Chips
- Evergreen Bark Mulch
- Straw or Hay (Clean, No Seeds)
- Cornstalk Pieces
I avoid using materials that can turn into a “mat” as they decay. Large deciduous leaves (maple, oak, magnolia) fall into this category. So does sawdust. Look for materials that are unlikely to create a smothering mat. We’re looking for a fluffy blanket, not smothering plastic wrap.
How to mulch perennials for winter
Once the foliage has been removed (or purposefully left standing), place a layer of mulch over the root crown, extending the diameter of the mulch patch a few inches beyond the plant. In our area (Zone 5), I added a solid 4” of mulch. By adding 4” of mulch, the roots are protected, but I can still see the top two inches of the stalks pe
The mulch patch and the stems poking out from it make it obvious that there is a dormant perennial in that location. If we lived in a colder zone, I might consider leaving 8” of the
Leave the mulch on top of the roots until spring. Wait until the danger of frost has passed, and temperature fluctuations around freezing are unlikely. Once temperatures are consistently above freezing, don’t delay in raking away the mulch from the base of the perennial. The mulch will trap warmer moisture and potentially create an environment for decay.
Most gardeners just place a few inches of mulch material directly on the plant’s root crown. For a little extra care, consider building a little structure over the plant to expand the amount of insulation. Create a frame with chicken wire, a tomato cage, or a flower pot. Stuff the frame with shredded leaves, straw, or another insulating material. This DEFINITELY should be done after the soil has frozen, or your little mulch house may attract rodents looking to hibernate.
Step 5: Store exotic perennials in a sheltered location
Some perennials just won’t survive winter outdoors in climates that freeze (or even have the odd frost). The last step in learning how to winterize perennials is to move these perennials to a sheltered location. Tender, exotic perennials aren’t meant to be grown year-round in cold climates. They won’t survive and will have to be replaced in the spring (which gets expensive!).
The foliage of exotic perennials will begin to die after the first frost. A hard freeze will leave them downright dead. The goal is then to get the roots out of the soil before the cold weather kills the root portions of the plants too.
Perennial plants that are often moved to sheltered locations for cold winters are:
- Canna Lily
These exotic perennials must be stored in cool, dry locations until springtime (after all danger of frost has passed). Even if a plant is moved from the garden to a sheltered location, there is no guarantee it will survive the winter.