Winter-Proofing Your Garden: Top Cold-Tolerant Container Plants

Who says gardening has to stop when the frost arrives and seasons change? Container gardening with crucial winter-proofing steps is a great way to keep those hands busy and the landscape beautiful. 

With the proper containers and protection, growers across the globe can keep their perennials, evergreen shrubs, and hardy ferns safe all year. Hardy perennials, shrubs, and flowers should remain outdoors during their dormancy, though it may be tempting to bring them indoors. 

Understanding Winter Container Gardening

Winter container gardening is growing cold-hardy perennials, shrubs, ferns, and even flowers during winter. This method requires shifting to a different watering and fertilization schedule and using appropriate containers that can withstand the outdoor elements. Winter container gardening keeps hands busy, perennials healthy, and your porch and landscape looking beautiful when the landscape is primarily shades of brown and white. 

The growing methods and what you select for your winter garden depend on your climate. For instance, in Zones 3 and 4, growers should choose containers that are more suitable to withstand rugged, long-term frosts and temperatures below freezing. In contrast, growers in Zones 6+ shouldn’t worry as much about container damage. Also, fluctuations that may occur in late fall and spring should be considered. Many areas have “second summer” and “false spring” periods of warmer weather, followed by plummeting temperatures, which can damage vulnerable new growth. 

Crucial things to know before starting a winter garden: 

• The limitations of your growing zone
• The first anticipated frost of fall and last frost date of the spring
• Your soil composition, which affects how it holds water and nutrients 
• Fertilization needs in the fall after a soil test analysis 
• Mulching needs

Related: The USDA’s New Plant Hardiness Zone Map - Explained

Best Cold-Tolerant Container Plants

Some plants are more cold and frost-hardy than others. Select them based on their ability to tolerate conditions in your region. Here, we’ll discuss perennials, evergreens, hardy ferns, and flowering plants for winter gardens. 

Perennials for Winter Pots

Heuchera is a perennial with a gorgeous array of color options. Growers in Zones 6b+ can overwinter them in containers. Check out our friend over at Visit Our Garden planting his Heuchera before winter sets in. 

Growers in colder regions should move potted heuchera into an unheated garage, a greenhouse, or under low-tunnels covered with greenhouse plastic or frost blanket to protect them from a hard freeze. The area should be cold enough to allow the plant to enter dormancy and may be dark or offer some sunlight. If you don’t have a protected outdoor area, try digging a hole and placing the potted plant into it, surrounding it with native soil, leaving the lip of the container or grow bag to remain above the soil surface, or tipping the pot into a dug trench and heavily mulching it for the winter, then removing it in the spring. 

Pro tip: Only attempt overwintering potted perennials in an unprotected outdoor setting if the plant is two zones hardier than your zone for best results. 

Hellebores (Helleborus argutifolius), or Lenten roses, are part of the buttercup family and bloom from February to April in most regions. Their blooms come in antique green shades to deep jewel-tone purples. Their foliage remains evergreen and is winter hardy in Zones 6+. Take extra care where winters are harsh, focusing on proper drainage and protecting the crown with compost and straw. When pruning berry bushes in late winter or early spring, also cut back old and damaged Hellebore growth to refresh them. 

Pro tip: Create a “huddle” of potted plants in a corner on the ground away from the wind path and cover it with mulch. Pots on the ground versus on a patio are safer from frost. 

Lavender (Lavandula angustifolia and latifolia) is a commonly grown herbaceous flowering plant native to the Mediterranean regions. Their uses include herbal medicine, sweet syrups and drinks, essential oils for salves and lotions, and dried flower crafts like crowns, flower panels, and scented sachets. With over 45 species, select one for your growing zone and climate for successful overwintering. Most won’t require much care and can tolerate various growing conditions, including poor soil. 

When harvesting is complete and your lavender plants have stopped flowering, cut back all the stems by early fall in preparation for winter. Pruning too close to a hard frost leaves your plant vulnerable to frost damage, so as a healthy habit, prune soon after you harvest your bounty. Using clean, sharp shears, cut back the stems two to three inches above the woody part of the plant so the plant is about ⅓ the size after pruning. 

If your lavender grew substantially throughout the season, step it up into a larger pot. The additional potting soil will add cold protection. Move the pot into a greenhouse or a perennial pot cluster and cover the crown with heavy mulch in cold regions. I’ve forgotten to mulch my lavender grosso plants in the past with no adverse effects, so even in my cold New England region, it survived outside with only a blanket of snow as insulation. 

Related: Best Time to Plant Lavender: Seasonal Pros and Cons for Flower Farmers

Evergreen Shrubs

Boxwood (Buxus sempervirens) is the low-maintenance shrub of my dreams. You can shape and trim it to the desired height, adding glossy, deep green winter interest and resistance to deer and rabbits. Plant them in mass to create a lovely privacy fence, elevate your lawn by planting solo boxwoods, or mix them into cottage and contemporary gardens. Test your soil to ensure the pH is between 6.5 to 7.2 and it drains well. 

In cold regions, plant them in an area protected from strong winds. Prune new growth off in late fall before a hard frost occurs to protect your boxwood from damage. Alternatively, wrap them in burlap sacks or winter tree wraps. It’s essential to clear heavy snow loads because while they can survive cold weather and light snow is an insulator, heavy snow and ice can cause breakage and permanent damage. 

Holly (Ilex opaca) is the perfect shrub to add to your yard for a festive vibe that doubles as winter food and a safe shelter for native birds. Identify holly bushes with their year-round shiny green, leathery, prickled edges and bright red berries. Pots of holly, especially young ones, are at risk of drying out in the winter, so shelter them from harsh wind and sunlight in growing zones colder than zone 5. A thick layer of mulch in my New Hampshire garden will help keep moisture in and protect my perennials and shrubs from desiccation. Water through the first frost to keep roots insulated. 

Pro tip: Use boxwood and holly clippings to make a holiday wreath or save them for December decor. 

Related: How to Forage Free Winter Decor

Junipers (Juniperus communis) are beginner-friendly evergreen shrubs. They need no special care before winter as long as the variety you choose is hardy in your growing zone and its pot is suitable for winter conditions. Snowfall should suffice for their watering needs and serve as an insulator. Mulch around the base after watering to retain moisture before the first hard frost. 

Juniper shrubs keep their needles year-round and only need to be pruned annually in late winter. Depending on how you design your containers, different varieties can be considered fillers, thrillers, or spillers. Use tall, showy varieties as the focal point of your winter container design. 

Hardy Ferns

When paired with proper decor, Christmas Fern (Polystichum acrostichoides) can add quite the festive vibe to your outdoor space or patio for the winter with its two-foot-long leathery fronds. It remains a deep, lush green through the December holidays and looks gorgeous, popping out through the snow grown alongside small berry bushes, woodland sedges, violets, columbine, or wild geranium. Christmas ferns are adaptable to most growing regions, conditions, and soil types and aren’t an invasive spreader. 

Autumn Fern (Dryopteris erythrosora) is a low-growing dwarf fern that transitions from autumnal copper and red shades to deep green, thriving in Zones 4 to 9, even after severe frosts. This fern will spread and appreciate a heavy compost top dress before winter. 

Pro tip: Add sprigs of faux berries or foraged pinecones for a seasonal twist.

Winter-Blooming Flowers

I used to think of pansies (Viola tricolor var. hortensis) as a summer flower because of their bright, cheerful “faces,” but then I learned just how hardy they were after allowing some to drop seeds and seeing them pop through spring snow! They don’t need much extra protection before winter arrives. However, if your region experiences harsh winters, a layer of mulch will help the soil retain moisture and keep the temperature consistent, reducing damage. Pansies are a great winter sowing candidate. 

Cyclamen (Cyclamen persicum) is native to southern Europe, western Asia, and parts of the Mediterranean. Breeders have given it the ability to perform well in pots, and its blooms range from white to pink to purple and red. The flowers are unique in shape and frilly patterns, resembling a butterfly in flight, and they bloom for about three months. However, this flowering plant is mainly grown as a houseplant in cold regions, so only warm zone growers should consider adding this to their outdoor winter landscape. 

Winter Jasmine (Jasminum nudiflorum) is a popular winter bloomer for tolerating poor soils and various soil types. It’s unique in that its bright yellow flowers bloom in January or February before the leaves appear. Growers should know they need regular pruning, or they’ll look unruly quickly. It can grow to four feet and produces many canes quickly. Like some berry bushes, flowers appear on old wood, so only remove wood older than two years old and those that are out of place when pruning. Winter Jasmine thrives in mass plantings, on slopes, trellised, or along stone walls.

Pro tip: Add some harvestable cold-hardy vegetables like cabbage and kale for a unique, practical spin. 

Related: Increase Your Urban Farm's Output with Container Gardening

How to Care for Winter Plants in Pots

Winter growers should adjust their watering and fertilizing schedules to align with plants’ needs and protect them from the elements as needed according to their growing zone and the species they’re growing. 

Watering Tips

Water your outdoor potted plants about once a month in areas that don’t experience much rain or snowfall. In colder regions where the soil may freeze, cease watering them in the winter. A crucial step in winter gardening is ensuring the containers have ample drainage. Soggy soil and drowning roots limit the plant’s uptake of nutrients, leading to stress, waterlogging, and potential death. Add compost to improve drainage and ensure the holes on the bottom of the container are large enough and unblocked. 

Related: How to Prevent Freezing Pipes: A Guide to Winterizing Your Garden's Drip Irrigation System

Fertilizing Guidelines

Most plants naturally enter dormancy in winter, so they need little or no fertilizer. A general rule is to stop fertilizing once new growth has stopped. You don’t want to encourage new growth that is vulnerable to winter damage. Water when the soil has dried, and only begin fertilization when spring growth starts again, following specific guidelines of your particular species and variety.

Protection From Elements

While snow will serve as a blanket of insulation and protect your plants, mulching in preparation for winter will help retain moisture, keep a consistent soil temperature, and minimize the amount of spring weed seed germination. 

Position potted plants, trees, and shrubs that need extra protection behind a natural or manufactured windbreak if you don’t have an indoor space available for the winter. Windbreaks include hedgerows of densely planted trees and shrubs, a fence, wall, or screen that redirects, minimizes, or blocks wind and snow. When appropriately positioned, windbreaks effectively block garden plots and farmland from erosion, wildlife damage, strong winds, rain, and snow while sequestering carbon and adding visual interest. For more information on windbreaks, this PDF from National Agroforestry Center has helpful information and links. 

Related: Backyard Gardening

Container Selection for Winter Plants

Selecting a suitable container for the job, in terms of material, size, and shape, is crucial to the plant's success through the winter. 

Choose the Right Material 

Select a material that will hold up to the elements. The best materials include plastic marked as frost-tolerant, fiberglass, and wood. Treated terracotta and clay pots are acceptable, but avoid using untreated ones, as they’ll crack under extreme temperatures and frost conditions.

Crucial features of the suitable material for your container include: 

• Durability: Will it hold up in the elements in your region? 
• Movability: Can you transport it from place to place? Are their handles? Can you manage the weight when it’s full? 
• Drainage: Are there holes in the bottom to allow excess moisture to drain? Will your pot crack in winter temperatures in your area? 
• Overall compatibility: Will the material control the temperature? Will it hold onto excess water? 

Consider positioning a breathable, movable fabric grow bag inside a more attractive pot or lining a larger pot with sand for additional insulation. Just make sure the bottom has drainage holes. If you choose terracotta, only select high-quality versions, which can last 10+ years, unlike their cheap counterparts. To test the quality, cover the bottom hold, tap the side with a fork or metal serving spoon, and listen to the sound it makes. Dull thuds indicate cheap terracotta. High-pitched ringing sounds mean it’s high-quality.

Growers may cover any pot with additional protection by wrapping them in burlap, frost blankets, or setting under cold frames.

Size and Shape Considerations 

Your plant will go dormant for the winter, but remember, their growth will take off in the spring when the snow melts, temperatures increase, and fertilization begins, so step up your plants in the fall in anticipation of this growth. Doing so will ensure the roots don’t become bound up, which leads to stress. 

Ensure that your shrubs and trees aren’t top-heavy, increasing the risk of being blown over in a wind storm. Since you may not water while plants are dormant, their soil becomes lighter, increasing this risk. Step them up into larger, deeper pots to avoid this. Selecting the right shape and size will alleviate the fear of your plants getting blown around, falling over, or becoming damaged. Adding a windbreak to block strong winds will help also reduce the risk. 

Common Challenges and Solutions

Now that you know how to prepare your plants for winter, here are some common issues that may arise and solutions for each. 

Frost Damage

Prevention from frost methods include: 

• Water plants until the first frost to keep roots healthy and reduce the risk of stress. 
• Select the proper container for your area. Don’t allow the container to crack. 
• Protect them as needed by moving containers to a greenhouse, behind a windbreak, into a cold frame, or wrapping them in a burlap blanket. 
• Mulch around the base of the plant to insulate the soil and help prevent the temperature beneath from dramatically fluctuating. 

If you suspect frost damage, bring it to a protected space to assess the damage. If this isn’t an option, reinforce protection by adding more straw around the base or an extra blanket layer. Then, wait until spring to assess the situation further. 

If the roots and stems are healthy, the plant should recover fine with some TLC. Prune as usual in late winter, removing damaged branches and limbs. Slowly begin to water to revitalize the plant, and fertilize when you see new growth. Fertilizing sooner may add more stress. 

Overwatering 

Common signs of overwatering include soggy soil, weak, limp roots, a sudden decline in overall health, halted growth, wilting, and yellow leaves. Overwatering results in more than just wet soil. It can lead to fungal diseases, pest issues, stunted growth, failure to uptake nutrients and thrive, and possible death.

To ensure you’re not overwatering, complete the two-finger moisture test weekly or bi-weekly by sticking your fingers into the soil to the depth of your first knuckle or just past. Water lightly if no soil is on your fingers and the plant shows signs of decline. However, if there is moisture below the surface two inches down, the plant has plenty of moisture even if the surface appears dry. 

Root Rot

Root rot can be difficult to detect, and it’s often too late to save the plant once it has occurred. You may suspect root rot if leaves are wilting, browning on the edges, stunted, yellow, or red. Growers can pull the plant from its pot and inspect the roots and surrounding areas. If they are mushy, smelly, or slimy, act swiftly. Remove infected roots using clean, sharp scissors or shears. Wash the roots to remove infected soil. Discard the old soil and, if using the same pot, wash and disinfect it before adding fresh soil. Re-pot the plant and prune back about ⅓ of the plant. Doing so allows the plant to focus on its root system rather than above-ground growth. 

Root rot prevention includes ensuring proper container drainage, avoiding overwatering, and dumping excess water so the roots aren’t sitting in standing water.  

Limited Sunlight

The tilt of the Earth’s axis causes hemispheres to experience less sunlight in winter than in summer, shortening the days. The sun sits lower in the sky, and shadows appear longer. To ensure your plants still receive enough sunlight to survive, position them in the most south-facing area of your property to ensure they receive six to eight hours of sunlight daily. 

To pinpoint the best area, monitor shadows in the fall to ensure no obstructions. Move them around as needed as the daylight changes. If your area does not receive enough sunlight, select shade-loving plants. 

FAQs

What are the best winter plants for pots?

Perennials like lavender, evergreen shrubs like boxwood, hardy Christmas ferns, and cold-tolerant flowers like pansies are all great options for winter container gardening. 

How often should I water my winter container plants?

In cold regions, watering should cease for winter, and you should rely on natural precipitation and snow melt to water your plants. Only water plants in winter if you live in a warmer climate and your plants cannot receive rainfall. Check the moisture level of the soil infrequently, monthly, or so. 

What containers are best for winter gardening?

Weather-safe and high-quality terracotta pots, fabric grow bags, and durable, frost-tolerant plastic are the best containers for winter gardening.

How can I protect my plants from frost?

Burlap sacks that cover plants entirely and securely, frost blankets, bed sheets, old blankets, and straw protect plants from frost. 

Can I grow flowers during the winter?

Yes, coral bells, lavender, hellebores, pansies, cyclamen, wintergreen, heuchera, primroses, and camellia are just a few winter-hardy flowers to consider for winter growing. 

Winter sow flower seeds that need vernalization to germinate correctly, as they would receive in nature. Simply sprinkle seeds over the surface or rake them into prepared garden beds in late fall or winter, as directed. The exact timing will differ by species. Winter sowing in milk jugs offers a more controlled environment. Flowers that readily self-seed are good winter sowing options. Common examples include larkspur, coneflower, foxglove, columbine, and milkweed. 

Written by Jenna Rich of Partners’ Gardens LLC.