Winter Annuals

Count on winter annuals to add color to the garden’s frosty—or even snowy—season. Learn which annuals survive winter cold.
Cabbages and Kales are Ornamental and Decorative

Cabbages and Kales are Ornamental and Decorative

Ornamental kale and cabbage are some of the most popular winter annual plants. They lend a completely different texture to a winter landscape bed. Once the plants are hardened by cooler night temperatures they can survive most cold winters.

©2011, Dorling Kindersley Limited

2011, Dorling Kindersley Limited

Make plans to add winter annuals to your containers and planting beds to keep the color coming strong all year long. Winter annuals go by many different names, including cool-season annuals, hardy annuals and frost-tolerant annuals. No matter what you call these blooming beauties, the result is the same: an extended growing season that infuses winter scenery with pops of eye-catching color.

The arrival of frost typically signals the end of the growing season in many regions. By stocking your garden with half-hardy and frost-tolerant winter annuals, you can prolong the garden season by a few weeks or even months, depending on the severity of your area’s winter. Reliable winter annuals may be half-hardy plants, which withstand a light frost (29 to 33 degrees F), or hardy plants, which withstand moderate (25 to 28 degrees F) to severe freezes (24 degrees F and colder).

Half-hardy winter annuals that thrive and sparkle in even the coldest regions (Zones 3 and 4) include China aster (Callistephus chinensis), godetia (Clarkia amoena), lobelia (Lobelia erinus), French marigold (Tagetes patula) and petunia. Hardy plants include calendula (C. officinalis), bachelor’s button (Centaurea cyanus), flowering stock (Mathiola incana), sweet pea (Lathyrus odoratus), swan river daisy (Brachyscome iberidifolia) and salvias of all types.

Choose hardy winter annuals to grace containers in the coldest zones during late fall’s early cold snaps. In mild winter regions, hardy winter annuals march steadily through winter’s coldest days with colorful style. Hardy winter annuals include snapdragon (Antirrhinum majus), pansy (Viola x wittrockiana), viola (Viola cornuta), sweet alyssum (Lobularia maritima), painted tongue (Salpiglossis sinuata), pinks (Dianthus chinensis) and nemesia.

For foliage color that even shrugs off early snows, plant dusty miller (Senecio cineraria) and flowering cabbage or kale (Brassica). Many herbs also stand as green sentries through winter cold and snow. These winter herbs include lavender (Lavandula angustifolia), thyme (Thymus officinalis), feverfew (Chrysanthemum parthenium), oregano (Origanum vulgare) and rosemary (Rosmarinus officinalis).

Winter Gardening Don'ts

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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.

Photo By: Gardener’s Supply Company

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.

Photo By: Proven Winners

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.

Photo By: Gardener’s Supply Company

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.

Photo By: Julie Martens Forney

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.

Photo By: Gardener’s Supply Company

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.

Photo By: Julie Martens Forney

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.

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Photo By: Julie Martens Forney

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.

Photo By: Julie Martens Forney

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.

Photo By: Burpee

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.

Photo By: Julie Martens Forney

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.

Photo By: Gardener’s Supply Company

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.

Photo By: Julie Martens Forney

It’s important to note, though, that even winter annuals survive coldest temperatures best when they’re established and have already experienced the gradual cool-down of fall’s transition to winter. If you purchase winter annuals from a greenhouse where they have been protected from fall’s chilly nights, you’ll need to harden off these beauties before planting them outdoors where they’ll encounter the nippy experience of frosty nights. A gradual exposure to colder temps is the secret to survival.

Always buy the largest winter annuals you can, especially in coldest regions, because plants won’t grow much once coldest temperatures settle in. When Jack Frost arrives and you wake to frost-covered annuals, don’t worry if plants look wilted or even fried. As the sun rises and air temperatures start to rise, winter annual plants recover. Winter pansies, for instance, can freeze solid for a few hours and recover as warm weather returns.

In coldest zones, once true winter arrives and temperatures hover in the teens and below, even most winter annuals won’t rise and shine. At that point, consider replacing plants in containers with arrangements of evergreen boughs, berried branches, ornamental grass stems, grain seedheads and pine cones. Add a few architecturally-interesting bare branches and white lights, and your winter containers will dazzle through the year’s darkest days.

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