Winterizing Strawberry Plants

Learn how to protect your strawberry plants for winter, including tips for dealing with plants in jars, barrels and pyramids.
Straw Mulch Keeps Strawberries Off Bare Soil

Straw Mulch Keeps Strawberries Off Bare Soil

Once strawberries begin to form, mulch the crop with straw to keep moisture in the soil and soil off the fruit.

©2011, Dorling Kindersley Limited

2011, Dorling Kindersley Limited

Protecting strawberry plants from winter’s cold temperatures is vital to ensure a crop of juicy berries next year. Winterizing strawberry plants isn’t difficult or expensive. It’s actually an easy chore on your garden to-do list. Learn tips for winterizing strawberry plants.

By the time fall frosts arrive, strawberry plants have already set buds for next spring’s flowers. Temperatures below 15° F can damage those new buds and diminish your berry crop next year. This is why it’s vital to winterize strawberry plants and protect them from cold winter air.

Another reason to protect plants is that, when soil repeatedly freezes and thaws, it tends to push plants up. This process is called heaving and puts plants at risk in several ways. First, it can expose plant crowns to drying air, freezing air temperatures and hungry critters looking for a winter meal. Second, heaving can break roots, allowing them to be lifted completely out of soil. Either results in plant damage or death. Winterizing strawberry plants helps prevent heaving.

Winterizing strawberry plants simply involves heaping mulch over plants so they’re not exposed to cold winter air. The trick is knowing when to apply the mulch. You want to cover plants when they’re fully dormant. Cover too soon, and plants may fail to harden off, which means they’ll definitely be damaged by cold air. A too-soon mulch also risks rotting plant crowns.

It’s safe to apply winterizing mulch to strawberry plants when the top one-half inch of soil has frozen and daytime temperatures stay consistently in the 20s. In mild winter areas, apply mulch once soil temperatures hit 40° F for three days in a row. Definitely winterize strawberry plants before temperatures dip below 20° F. Precise timing varies depending on region. Fine-tune the timing with a call to your local extension office. 

To winterize strawberry plants, heap a loose mulch over plants to a depth of 3 to 5 inches. Use a material that won’t compact heavily. Good choices include straw, clean hay, bark chips, chopped cornstalks or cobs, evergreen branches or pine straw. Materials like leaves or grass clippings aren’t a good choice because they tend to mat. After mulch settles, it should still provide a 2- to 3-inch depth for best protection.

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

Using a frost blanket to winterize strawberry plants is another great choice because it allows light to reach plants, which results in more flower buds being formed. The tricky part is that plants experience faster flower development in spring, which means they’ll be at greater risk for cold damage if you fail to protect plants when a late-season frost is predicted.

To winterize strawberry plants in a pyramid, apply mulch 6 to 8 inches deep. Wrap large strawberry pots or barrels with burlap and/or bubble wrap and stuff the top opening with straw 6 to 8 inches deep. Move strawberry jars into an unheated garage for winter.

Remove winterizing mulch in spring as growth resumes. Consider raking it into rows and around plants to serve as a growing season mulch. Keep it nearby in case you have to heap it over plants again in the event of a late spring frost.

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