Winterizing Plants

Discover easy techniques for getting plants ready for winter’s chill.

Mulch Ground Cover

Mulch Ground Cover

Photo by: DK - The Complete Gardener's Guide © 2011 Dorling Kindersley Limited

DK - The Complete Gardener's Guide , 2011 Dorling Kindersley Limited

Prepare your garden for cold weather to come by winterizing plants. Many of your prized garden stars survive winter without extra care on your part, but taking time to winterize paves the way for a healthy, productive garden next spring. For tender plants and new additions to the garden, winterizing is vital for cold weather survival.

Start the winterizing process by mulching around landscape plants. Mulch helps insulate soil and prevent frost heave, a condition that occurs when soil repeatedly freezes and thaws—and pushes plants out of soil. When frost heave occurs, plant crowns and roots are exposed to freezing air and drying winds. 

When you add fall mulch, aim for a layer that’s 3 to 5 inches deep (deeper in colder regions). Use a material that won’t compact, like straw, chopped leaves or cornstalks, pine straw or clean hay. It’s especially important to mulch shallow-rooted perennials that are prone to frost heave, like blanket flower (Gaillardia), coral bells (Heuchera), pincushion flower (Scabiosa) and shasta daisy (Leucanthemum). Do not mulch bearded iris.

While you’re adding mulch, take time to cut down perennials and pull annuals. This aspect of winterizing plants helps eliminate hiding places for pests and diseases. Leave any plants that add winter interest with seedheads or stems, but clean up as much as possible.

Winterizing plants like roses or newly-planted perennials requires protecting plant crowns with a deeper layer of mulch or soil after the ground freezes. You may want to create a framework around plants using chicken wire, hardware cloth or tomato cages that you stuff with leaves or straw to protect plant crowns. Always wait for soil to freeze before doing this, or you risk creating a hibernation haven for rodents.

In cold weather, evergreen roots freeze in soil and stop taking up water. Winterizing evergreen trees and shrubs involves protecting them from drying winter winds. To do this, erect a burlap screen on the windy sides of plants (usually the west and north). Drive stakes into soil before it freezes, and come back when temperatures are steadily in the 20s to staple or zip-tie burlap to stakes.

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

Wrap young trees, especially ones with thin bark like fruit trees, soft maple and honey locust, to prevent sunscald. Use a commercial crepe paper-type tree wrap and apply it from the soil line to the second or third branch. Overlap edges as you wrap so it sheds water. Anchor the wrap with a small tack or weatherproof tape.

For tender shrubs and perennials, protecting roots can help plants survive. Build a small screen around plants, heap soil over roots and stuff the screened-in area with leaves or straw. For some tender perennials, cut back top growth and place a layer of packing foam over the plant crown, topped with several inches of soil. Once that freezes, add a mulch layer for extra protection. Use this method to overwinter plants like lantana, pineapple sage or lemon verbena in borderline zones.

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