Plant Covering Materials – Ideas For Covering Plants In Cold Weather

Plant Covering Materials – Ideas For Covering Plants In Cold Weather

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By: Mary H. Dyer, Credentialed Garden Writer

All living things need some sort of protection to keep them comfortable during the winter months and plants are no exception. A layer of mulch is often enough to protect plant roots, and in more northern climates, Mother Nature provides a layer of snow, which serves as a great winter covering for plants. However, many plants depend on a little extra protection to survive until spring. Read on to learn about covering plants in cold weather.

Is Covering Plants in Cold Weather Really Necessary?

Frost covering for many plants is of limited use, and the best way to protect plants, according to horticulturalists at University of Georgia Extension, is to ensure your plants are properly watered, fed and protected from pests during the spring and summer.

Healthy plants are hardier and can withstand cold weather better than weak, unhealthy plants. Most importantly, plan carefully and choose plants that can survive in your growing zone.

If you use plant covering materials, use them only during the cold spell and remove them as soon as the weather moderates.

Young evergreens can suffer sunscald for the first two to five winters. A light-colored winter covering will reflect the light and keep the bark at a relatively consistent temperature. Be sure to water evergreens deeply before the ground freezes, as evergreens are unable to replace moisture lost to winter wind and sun.

Types of Winter Covering for Plants

Here are the most common plant coverings for protecting plants in cold weather or frosts.

  • Burlap – This natural fiber is an effective winter cover for marginally hardy plants and works well as protection for young shrubs and trees. Wrap the burlap loosely around the plant, or better yet – create a simple tepee of stakes, then drape the burlap around the stakes and secure it with twine. This will prevent breakage that can occur when burlap becomes wet and heavy.
  • Plastic – Plastic is definitely not the best winter covering for plants, as plastic, which doesn’t breathe, can trap moisture that can kill the plant in a freeze. You can use plastic in a pinch, however (even a plastic garbage bag), but remove the covering first thing in the morning. If a sudden cold snap is predicted, an old sheet or a layer of newspapers offers safer protection than plastic, which can do more harm than good.
  • Polypropylene or polypropylene fleece – You can find many types of polypropylene plant covering materials at garden supply stores. The covers, often known by names such as garden fabric, all-purpose fabric, garden quilt or frost-protect, are available in various thicknesses with varying degrees of protection. Polypropylene is useful in many cases because it is lightweight, breathable, and allows a certain amount of light to enter. For large applications, it is available in rolls. It can be laid directly on the ground or wrapped around a framework made of stakes, bamboo, garden fencing, or PVC pipe.

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Read more about Environmental Problems

Winter Cover Cropping : A Fine Time to Build Soil

Winter is a good time to be working on soil improvement, and you don't have to go out in cold weather to do it!

By planting a cover crop in summer or fall and letting it overwinter, you can:

  • Improve soil organic matter and soil fertility.
  • Suppress cool-season weeds.
  • Prevent soil erosion.
  • Create a better seedbed for spring planting.

The best winter cover crops differ from region to region, by growing zone and the crop's winter hardiness, but from a management perspective there are basically two types, winter-killed and winter-hardy, along with a third, blended type of the two.

1 • Winter-killed cover crops: Killed by cold, but have sufficient biomass to protect the soil.

Oats are an prime example of this first type. Sown in summer, they will put on a lot of growth, and often maintain active growth into early November, dying slowly after several hard frosts. The winter-killed mulch and root mass will hold the soil in place, however, until the following spring.

The caveat with this type of cover crop is that you have to clear the land and plant the cover crop early enough to get significant amounts of biomass to hold the soil over the winter. That could mean winter cover-cropping only on ground that grew spring vegetables, or it could require undersowing the cover crop in a summer crop such as corn. The big advantages of a winter-killed cover crop is that the mulch is easy to till under in spring, and the land can be planted right away.

2 • Winter-hardy cover crops: Survive through winter, resume growth in spring.

  • Establishes ground cover quickly.
  • Hardiest winter cover crop to stem wind & water erosion.
  • Deep & extensive root structure prevents compaction, improves soil tilth.

The second, winter-hardy type can either grow through winter or go dormant for a period when temperatures and/or daylight reach a certain threshold, then renew growth in late winter.

They can usually be planted after the summer vegetable crops, and will grow through fall to establish root systems that protect the soil from the dynamic forces of wind and water over winter.

Some examples of crops that will survive the winter — depending on winter temperature lows — include winter rye, winter wheat, hairy vetch, Austrian winter peas, and crimson clover. Winter rye and hairy vetch are recommended for the northern United States.

In regions where these crops survive winter, they will grow vigorously in early spring. They will need to be mowed close to the ground, to stop growth, and then incorporated into the soil. Because decomposition of the cover crop debris will tie up nitrogen, it's a good idea to wait two or three weeks before planting.

Mixed winter-hardy & winter-killed cover crops

Many growers use a mixture of cover crops from the two categories. Johnny's Fall Green Manure Mix is a blend of winter rye, field peas, ryegrass, crimson clover, and hairy vetch. The peas, clover, and ryegrass will be winter-killed. The rye and hairy vetch will regrow in spring.

Winter forage

If deer are numerous in your area, take note that they tend to prefer winter rye over almost all other winter cover crops. As an alternative to winter rye, you may want to consider sowing a mixture of medium red clover and oats, as the deer do not like oats as much.

Another practice is to sow forage turnips around the perimeter of the field, to satisfy the deer's hunger. Sown by mid-August, turnips will generally grow slowly until temperatures fall below 20°F/-6.6°C. While the turnip bulbs will remain grazeable even after freezing, they will begin to deteriorate soon after a thaw.

Root injury

Roots do not become dormant in the winter as quickly as stems, branches and buds, and roots are less hardy than stems.

Roots of most trees and shrubs that grow in Minnesota die at temperatures at or below 0 and up to 10 degrees. These plants survive in Minnesota because soil temperatures normally are much higher than air temperatures and because soil cools down much more slowly than air temperature.

Many factors influence soil temperature.

  • Moist soil holds more heat than dry soil, so frost penetration will be deeper and soil temperatures colder for sandy or dry soils.
  • Snow cover and mulch act as insulators and keep soil temperatures higher.
  • With newly planted trees, cracks in the planting hole allow cold air to penetrate into the root zone, reducing fall root growth or killing newly formed roots.

Reducing root injury

  • Cover roots of newly planted trees and shrubs with 3 to 4 inches of shredded wood mulch.
    • Create a "donut" of mulch by pulling the mulch away from the trunk about 6 inches.
    • This will prevent adventitious roots from forming and ultimately girdling the tree.
  • If the fall has been dry, water heavily before the ground freezes to reduce frost penetration.
  • Check new plantings for cracks in the soil and fill them with soil.

Frost heaving

Repeated freezing and thawing of soil in fall or spring causes soil to expand and contract, which can damage roots and heave shrubs and new plantings out of the ground. A 4- to 6-inch layer of mulch will prevent heaving by maintaining more constant soil temperatures.

Winter injury to deciduous trees

Sunscald happens when there are elongated, sunken, dried or cracked areas of dead bark, usually on the south or southwest side of a tree.

On cold winter days, the sun can heat up bark to stimulate activity. When a cloud, hill or building blocks the sun, bark temperature drops rapidly, killing the active tissue.

Trees susceptible to sunscald

  • Young trees, newly planted trees, and thin-barked trees (cherry, crabapple, honey locust, linden, maple, mountain ash, plum).
  • Older trees are less subject to sunscald because the thicker bark that can insulate the tissue remains dormant and cold hardy.
  • Trees pruned to raise the lower branches, or transplanted from a shady to a sunny location, because the lower trunk is does not have shade.

Sunscald prevention

Prevent sunscald by wrapping the trunk with white guards to reflect the sun and keep the bark at a more constant temperature.

  • Use a white commercial tree wrap or plastic tree guards. Do not use brown paper tree wrap or black colored tree guards as they will absorb heat from the sun.
  • Wrap newly planted trees for at least two winters and thin-barked species up to five winters or more.
  • Put the wrap on in the fall and remove it in the spring after the last frost.

Sunscald repair

Trees will typically heal themselves through new growth of the inner bark or along the edges where the bark split. However, it may be necessary to repair the damage.

  • Sterilize a sharp knife by dipping in 10% bleach solution (1 oz. bleach, 9 oz. water) or soak in 70% alcohol for 3 minutes.
  • Following the general shape of the wound, use the knife to remove dead bark to reveal live tissue. Rounding off any sharp corners to facilitate healing .
  • Leave the wound uncovered. Do not apply paint, tar or a commercial tree wound dressing to the open wound.
  • If the type of tree is susceptible to a fungus, spraying the area with a fungicide may help prevent fungal infection of the wound.
  • Encourage good tree health and growth by fertilizing it in the spring, mulching the root area, and watering during dry weather.
  • Wrap the tree in winter to prevent further sunscald.

Deciduous trees and shrubs can suffer shoot dieback and bud death during the winter.

Flower buds are more susceptible to injury than stem or leaf buds. A good example of this is forsythia, where plant stems and leaf buds are hardy, but flower buds are very susceptible to cold-temperature injury.

Minimizing dieback

Little can be done to protect trees and shrubs from winter dieback.

  • Put plants that are marginally hardy in sheltered locations.
  • Plants in a vigorous growing condition late in the fall are most likely to suffer winter dieback, so avoid late summer pruning, fertilizing, and overwatering.
  • Fertilize in the spring on sandy soil or in the fall on heavy soil after the leaves have dropped.

Winter injury to evergreens

Brown or bleached out evergreen foliage

Discoloration of evergreen foliage during winter may be caused by:

Winter sun and wind cause excessive foliage water loss while the roots are in frozen soil and unable to replace lost water. This results in desiccation (drying out) and browning of the plant tissue.

Bright sunny days during the winter warms plant tissue, which in turn initiates cellular activity. Then, when the sun sets or goes behind clouds, foliage temperature can drop, injuring or killing the foliage.

Bright, cold winter days destroy chlorophyll in the foliage. The chlorophyll does not re-synthesize when temperatures are below 28 degrees. This results in a bleaching of the foliage.

Cold temperatures occurring early in the fall before plants have hardened off completely or in late spring after new growth has occurred can result in injury or death of this non-acclimated tissue.

Leaf damage normally occurs on the south, southwest, and windward sides of the plant, but in severe cases it may affect the whole plant.

Yew, arborvitae, and hemlock are most susceptible, but winter browning can affect all evergreens. New transplants or plants with succulent, late season growth are particularly sensitive.

How to reduce evergreen winter injury

When evergreen winter injury has occurred

Brown foliage is most likely dead and will not green up. But the buds, which are more cold hardy than leaves, will often grow and fill in areas.

  • Wait until mid-spring before pruning out injured foliage.
  • If the buds have not survived, prune dead branches back to living tissue.
  • Fertilize injured plants in early spring and water them well throughout the season.
  • Provide appropriate protection the following winter.

Damage caused by snow, ice and salt

Heavy snow and ice storms cause damage by bending and breaking branches. Trees that are most susceptible to snow and ice damage include:

  • Trees with more than 1 central leader (main stem)
  • Upright evergreens such as arborvitae and juniper
  • Trees with multiple stems (clump) such as birch
  • Trees with poor form such as narrow branch crotches and included bark

Preventing snow and ice damage

  • Wrap relatively small trees together or tie the leaders with strips of carpet, strong cloth or nylon stockings two-thirds of the way above the weak crotches. Remove these wrappings in spring to prevent girdling, and to allow free movement of the stem.
  • Proper pruning, to eliminate multiple leaders and weak branch attachments, will reduce snow and ice damage.
  • For trees with large wide-spreading leaders or large multi-stemmed trees, a professional arborist should cable the main branches together.

Minnesota is reducing the use of salt (chloride) for deicing walks and roads in an effort to reduce the negative effect on our environment, especially our water. It can cause or aggravate winter injury and dieback of trees and shrubs through salt runoff from roads, and by salt spray from traffic and snowplows. Runoff leads to salt buildup in the soil that can injure roots and be absorbed by the plant, ultimately damaging the foliage. Salt spray can cause severe foliar or stem injury.

Preventing salt damage

  • Do not plant trees and shrubs in areas where salty runoff collects or close to streets where salt spray is prevalent. Burlap barriers may provide protection to some plants from salt spray.
  • Avoid or reduce the amount of de-icing salts used on walkways by clearing areas of snow as soon as possible. Apply the minimum amount of salt needed and only where needed. Avoid spreading salt on grass and in ditches where water collects.
  • Use alternative de-icing salts such as calcium chloride and calcium magnesium acetate (CMA).
  • Use salt-tolerant plant species near walks and roads where salt may be applied. Remember that no species is completely tolerant of salt injury and that even salt-tolerant trees have limits on the amount of salt they can handle. Consider some of these more tolerant species:
    • Ohio buckeye, Austrian pine, ginkgo, honey locust, black walnut, Black Hills spruce, jack pine, white poplar, black locust, Japanese tree lilac, black cherry, white oak, northern red oak
  • Keep plants healthy throughout the year.
    • Provide adequate irrigation and mulching to reduce water loss.
    • Prune and add fertilizers to correct nutrient deficiencies.
    • Control damaging diseases and pest infestations.

Reducing animal damage on trees and shrubs

Mice, rabbits, voles and deer can all cause severe damage to plants in the winter by feeding on twigs, bark, leaves and stems. They can eat shrubs to the ground and also girdle trees and shrubs by chewing through the bark.

The best overall strategy for protecting your trees and shrubs from animal browsing is to reduce areas of habitat and erect physical barriers to prevent them from getting to your plants.

Reducing animal damage on plants starts with eliminating protective cover and a desirable nesting environment.

  • Cut grasses and other vegetation short in late fall within 2 feet of young trees to reduce protective cover for mice and voles that might feed on trunks and stems.
  • Discourage rabbits from taking up residence in your yard by reducing protective cover, removing brush piles, and fencing off other hiding places such under decks and other structures.

Put up physical barriers to keep animals away

Protect tree trunks with cylinders of ¼-inch mesh hardware cloth around the trunk of the tree about 6 inches away from the trunk. This can be kept on year-round.

  • For mice, the cylinder should extend 2 to 3 inches below the ground line.
  • For rabbits, the cylinder should extend 18 to 24 inches above the anticipated snow line.
  • Make sure there are no gaps between the bottom of the mesh cylinder and the ground where animals could crawl under the fencing.
  • For small trees, plastic tree guards are also effective.
  • Protect shrubs from rabbits by fencing the beds with hardware cloth.
  • Enclose the lower branches as well as the trunk.
  • Check fenced areas frequently to make sure rabbits aren't trapped inside.

Caring for overwintering plants:

The key to overwintering is keeping the plants cold and alive but not actively growing. After the plant's chilling requirement has been satisfied, plants can respond to warm temperatures. In late winter as the temperature increases, plants can de-acclimate to cold temperatures. If the temperature decreases slowly, plants can re-acclimate to colder temperatures but fast drops in temperature can cause cold injury to plant tissue. Although white polyethylene covered houses warm up less, vent the house by opening the end doors if the inside temperature approaches 45-50°F.

Plants should not be uncovered until after the danger of subfreezing temperatures. In early spring, some growers cut holes in the poly to ensure adequate ventilation while still providing adequate protection from frosts. Although difficult, it is important to check that growth of plants under structureless systems has not started. Depending on the materials used to protect plants, some coverings can have a high insulating value that is effective at retaining heat. Etiolated growth can occur and be very susceptible to cold injury. By uncovering, the plants will remain dormant. This can be a nuisance where mild temperatures occur periodically during the winter.

A Mound of Mulch

Heaping a mound of mulch over the crowns of low-growing ground covers and small plants keeps a light frost from touching the tender leaves. Most gardeners cover the mulch with plastic sheeting or a tarp to keep the mulch dry. A few well-placed rocks or bricks will prevent the plastic from blowing away in the harsh winter winds.

Alternatively, use discarded holiday tree trimmings or other prunings from the fall, both of which can provide a good cover for larger plants. Even hardy plants can benefit from being mulched over the winter, as they may recover more quickly and flower before they might have.

Extra-Cold Climates

In areas where winter means sub-zero temperatures and frigid, drying winds, you may need to take more extreme measures to help your roses survive.

1. After the first frost, bundle the canes together and tie them with twine to hold them upright as you work. Use a garden fork to gently unearth the plant's roots. Dig a trench to one side of the rose large enough to contain the height and width of the plant.

2. Gently tip the plant on its side and lay it in the trench. Cover it with soil. Pile a 2-inch layer of shredded leaves on top of the soil. In early spring, carefully uncover the rose and replant it.

Watch the video: Winter Protection Part 2 Cold Frames


  1. Verge

    Thanks so much for the information, now I know.

  2. Justyn

    In gonivo

  3. Geraghty

    Who knows.

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