Plant Covers for Winter
Discover tools and techniques you can use to protect your plants from frost and extend the growing season.
Keep your plants safe from frost by using winter plant covers. These chill-chasing covers give plants a cozy hideaway that’s warmer than surrounding air. The difference is often only a few degrees, but those degrees make a big difference. Protecting plants from freezes isn’t difficult. Learn ways to help your plants survive frosts.
One of the most common winter plant covers is a frost blanket or floating row cover that you toss over plants before a freeze arrives. Frost blankets work by excluding cold air and creating an insulating air pocket around plants. Heat from soil, which is warmer than air, is trapped beneath the blanket and held near plants.
These cold-defeating fabrics are made from a woven polypropylene that’s lightweight and breathable. The material allows sunlight and water to reach plants, but keeps frost out. Most of these winter plant covers are also UV-stabilized. This means the materials won’t break down quickly when exposed to sunlight and can be used for several growing seasons.
Frost blankets come in varying thicknesses. Thicker blankets protect plants to a greater degree than thinner ones. Thicker blankets also exclude more light. Thinner frost blankets typically protect plants to 28° F and permit 70 percent of sunlight to reach plants. Thicker blankets protect plants from 24 to 26° F and allow 30 percent of sunlight to reach plants. It’s most economical to purchase frost blanket rolls 20 to 100 feet long, 6 or 12 feet wide. Cut the fabric into custom sizes, and sew pieces together as needed to form larger blankets.
Although frost blankets can lie directly on plants, you’ll get the best protection when you create a framework that holds the winter plant covers above plants. Build a temporary or permanent framework using flexible PVC pipes slid over pieces of rebar driven into the ground. Or drape the blanket over short wire garden fencing. Using materials you have on hand is the secret to creating an inexpensive support system.
When using a frost blanket, be sure to anchor the edges to exclude all cold air. Hold edges down with landscape pins, bricks, lumber or other available materials. Or bury edges in a shallow trench, anchoring them with soil.
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.
You can also find winter plant covers specifically designed to slip over hanging baskets and container plantings. Drawstrings with cord locks allow you to cinch the cover closed. Like other frost blankets, these covers come in various sizes and thicknesses.
Plant covers for winter prove invaluable on both ends of the growing season. Use them in early spring to protect newly planted seedlings from late-season frosts or to give them a toasty mini-greenhouse atmosphere as they establish. In fall, draft frost blankets to get plants through an early cold snap or to create a frost-free growing environment to extend the garden season. Frost blankets are an excellent tool for growing a winter vegetable garden.