Winter Container Gardens
Dress up a few containers with cool-season flowers, vegetables and herbs, to keep the color coming as winter arrives.
Spruce up the cool season of the year with winter container gardens. These pretty pots more than earn their keep by injecting a splash of much-needed color into frosty landscapes. Winter container plants stand up to light and even hard freezes, depending on their location and the duration of the cold snap. In milder winter regions (Zones 7 to 10), you can expect to enjoy winter container gardens through the New Year and beyond.
When creating winter container gardens, be mindful of two key things: soil and plant selection. Using the right soil is important because plants that grow through winter don’t actually grow that excessively, except in the warmest zones. In areas where temperatures hover in the 40s during the day and dip into the upper 30s at night, plants remain more in a resting state. Winter container plants form new flowers and cold-hardy greens produce new leaves, but the growth won’t be as intense or fast as in spring, when days are longer, the sun is warmer, and days shake off winter’s chill.
For this reason, it’s important to use a quality soilless mix in your winter container gardens. Because plants aren’t growing vigorously, soil must drain well. Otherwise, you’re assigning roots to soggy, heavy soil—and the root rot that usually occurs in those conditions. Try to avoid soil mixes containing moisture retention granules, especially if your winter is a rainy season, like in the Pacific Northwest. Blending composted organic matter into pots is a great idea to help enhance drainage.
Ideally, you want to design your pots using winter container plants that stand up to light frosts. Half- or semi-hardy plants withstand light frosts (29 to 33° F) without damage; hardy plants can take a hard freeze (25 to 28° F). Semi-hardy annuals include lobelia, petunia, diascia, China aster and French marigold. Hardy winter container plants include calendula, flowering stock, swan river daisy, pansy, pinks, sweet alyssum, painted tongue and viola.
Also consider adding vegetables and herbs to your containers. They yield a harvest while adding color to winter scenery. Leaf lettuces, Asian greens, kale, spinach, arugula and mustard and collard greens make an excellent showing as temperatures tumble. Herbs that thrive in winter container gardens include thyme, parsley, oregano, lavender and feverfew.
Mistake No. 1: Planting Too Late
Making late additions to the landscape can result in devastating losses next spring, especially in areas where the ground freezes. Perennials are the most susceptible to late planting, as alternating freezing and thawing of soil literally shoves plants out of soil, exposing crowns. Shrubs and trees can go into the ground later, but for best winter survival rates, you should have all plants in place by six weeks before soil typically freezes.
Mistake No. 2: Pruning Shrubs
Pruning causes plants to produce new growth, which is tender and highly vulnerable to freezing temperatures. Wait to prune shrubs, including butterfly bush and caryopteris, until spring, when all danger of frost has passed. At that point you can remove any winter killed branches. In future years, aim to get pruning done by late August, so plants have time to harden off before freezes arrive.
Mistake No. 3: Planting the Wrong Varieties
Fall lettuce crops can linger well into December in mild winter areas. Plant cold-tolerant varieties to ensure the longest harvest period. Good choices for fall planting include ‘Four Seasons’ lettuce (shown), ‘Arctic King’ and ‘North Pole.’ To overwinter lettuce in regions with cold winters, plant ‘Winter Marvel’ or ‘Brune d’Hiver.’ In mild winter areas, sow seeds of ‘Four Seasons’ or any oakleaf type.
Mistake No. 4: Not Watering New Trees
Trees that you plant in fall need consistent watering as they enter their first winter. If winter brings frozen soil without snow, give your tree a drink during any times of above-freezing temperatures. One hose-less way to ferry water to a tree is with a water bag in a cart.
Mistake No. 5: Failing to Deadhead Self-Sowers
Plants that self-sow aggressively in the landscape can be beautiful in bloom, but a gardener’s nightmare if allowed to go to seed. Clip seedheads on plants that tend to self-sow heavily in your garden. Good candidates include joe-pye weed, goldenrod, boltonia and black-eyed susans.
Mistake No. 6: Skipping Mulch
A winter mulch can be a gardener’s best friend, especially around new additions to the landscape. That extra mulch layer can help prevent frost heave around new plants that may not have an extensive root system to help keep them anchored in soil as it freezes and thaws. Put a 2-inch-thick layer around the base of plants to insulate roots.
Mistake No. 7: Spraying for Weeds
Be sure to read the label of your favorite weed killer. For common chemicals like Round-Up, 50°F is usually the lowest temperature where the product remains effective at killing weeds. Many plants essentially stop growing as soil temperatures fall into the 50-degree range, so at that point spraying is a waste of time and money. The answer is to spray early in the fall season, while plants are actively growing and air temps are still in the ideal 60-degree range.
Mistake No. 8: No Pre-Snow Clean-Up
In snowy winter climates, aim to clean up the garden before early snowfalls arrive. Doing this helps to reduce winter resting places for pests and diseases that go into hiding once snow flies. It’s also easier on you—no frozen fingers.
Mistake No. 9: Not Destroying Veggie Crops
It’s vital to destroy spent vegetable crops, especially those that hosted problem pests, like Mexican bean beetles. Don’t toss these plants into a compost pile unless you know it heats enough to destroy pests and eggs. It’s safer to dispose of infested plants and fallen leaves in bags you put at the curb for garbage pick up.
Mistake No. 10: Failing to Use Frost Blankets
If you have a garden that’s actively producing when frost threatens, there’s no excuse for not investing in some season extending equipment to keep the fresh flavors—and nutrition—coming into your kitchen. This kit costs under $25 and comes with built-in hoops and the ability to extend up to 18 feet.
Mistake No. 11: Letting Grass Grow Too Long
In snowy regions, grass that goes into winter without being mowed is more prone to develop snow mold. Try to give grass one last cut before winter snows arrive. Also, once the ground freezes, stay off the lawn. Frozen grass is more prone to breaking as you walk on it, which can damage individual grass crowns.
Mistake No. 12: Not Wrapping Vulnerable Shrubs
Take time to wrap shrubs and small trees with a winter coat of burlap for protection against cold temps. Plants at risk include those with borderline hardiness and evergreens prone to winter burn. Spray evergreens with an anti-transpirant before wrapping in burlap. Before adding the burlap, protect trunks against chewing rodents by tossing mouse bait that’s enclosed in a protective container near the base of the plant.
Mistake No. 13: Failing to Protect Trunks
As food sources become scarce, rabbits, mice and voles can make quick work of bark on unprotected trees and shrubs. Use tree guards around young tree trunks, and surround shrubs with hardware mesh. You can also try to attract raptors like owls and hawks, which prey on these mammals, by erecting artificial perch poles.
Don’t hesitate to intermingle flowers, vegetables and herbs. Pansies pair beautifully with parsley and leaf lettuces. A simple planting of deep green-black Tuscan kale with flowering stock and sweet alyssum will make you smile all winter long. Pots filled with painted tongue or diascia bloom like carnivals, overflowing with cheerful color. Place them in groupings with containers filled with mustard greens—including red mustards, like Red Giant and Osaka Purple—for a stunning display.
Search for the largest plants you can find in colder zones, especially if you’re planting late. You want to start large knowing that plants won’t grow intensely once cold weather arrives. In Zones 7 to 10, where winters are warm, feel free to start with pack-size annuals and vegetables. They’ll have a long winter season to fill out, and they gradually will.