Various types of materials are used to protect plants. Avoid plastic coverings, as they trap moisture and encourage rot, as well as dark coloured materials, which can overheat. The following section contains a description of useful and effective materials for winter protection.
Organic mulch
Organic mulch is used to protect the roots of trees and shrubs from successive freezing and thawing, which can be especially hard on bare soil. It can also be used to completely cover perennials that are not protected by a good blanket of snow or that aren’t naturally very cold resistant.
Usually, a 10 to 15 cm thick layer of mulch (shredded leaves, cocoa or buckwheat hulls, etc.) should be placed around trees and shrubs needing protection. It is important not to cover the base of the trunk.
Perennials requiring protection can be covered with a layer of mulch (10 to 15 cm) once the ground is completely frozen. Remove the mulch as early as possible in spring.
Evergreen boughs
Snow will tend to accumulate on piles of evergreen boughs, especially in very windy locations. This makes them useful for protecting plants vulnerable to freezing rain and apt to become waterlogged by melting snow (alpine plants, thyme, lavender, sage, etc.).
Plastic and wire mesh
Plastic or wire mesh is a good way to prevent rodents from gnawing on tree bark over the winter. You will need to think about how much snow is likely to pile up, and cover all parts of the plant (trunk and main branches) that rodents might be able to reach. Remove the protection in spring.
Protective netting and jute twine
Plastic netting for conifers prevents the crowns from opening and hence damage caused by the weight of snow and freezing rain on branches. It is used to cover plants that don’t need protection from wind and salt spray. The advantage of such netting is that it is not too visible. Avoid over-tightening the netting around conifers and plants that retain their leaves, to prevent trapping moisture in the centre of the plant that could promote disease.
Instead of netting you can also tie up shrubs with jute twine to protect them from freezing rain and wet snow. Start by tying the twine to a bottom branch and winding it around the shrub to form an upward-pointing cone.
Wooden snow fencing
Snow fencing protects plants from the weight of snow and freezing rain. It is an especially good way of protecting plants in the line of snow shot from a snowblower or falling off a roof. It is also used to support protective covers.
Snow fencing is made of wooden slats arranged vertically and held together with horizontal metal staples. A four-foot-high snow fence should contain a minimum of five staples. When buying snow fencing, you should also consider the type of wood used for the slats and the number of slats per linear foot. Fencing made with softwood (poplar) slats rots quickly. Spruce slats are more rot-resistant, but are heavy and breakable. Cedar-slat fencing is light and highly rot-resistant, but more expensive. Finally, some fencing has up to 25% more slats per linear foot and thus offers better protection.
Synthetic tarps
Commonly known as geotextiles, these tarps are made from polyester felt with an applied surface finish. They protect plants from harsh cold snaps, when bitter temperatures and drying winds can cause severe damage to plants susceptible to drying out over the winter.
You can make a shelter around one or more plants by installing stakes and snow fencing to support a tarp. The tarp mustn’t be allowed to touch the plants, however, as it conducts the cold and looses its effectiveness if is covered in ice. The fabric is also permeable to salt spray.
Plastic-coated tarps
These tarps are made of polyester felt coated with waterproof white plastic (LDPE). They offer excellent protection from salt spray and drying winds that are especially hard on conifers and plants that retain their leaves. The plasticized side should be placed facing out, to give snow and ice less chance to accumulate.
Lawn tarps
These tarps, which are usually green, protect lawns from winter abrasives and make spring clean-up easier.
Trunk coil guards
Polyester coil guards are used to prevent the bark on the trunks of young trees from splitting.
Polystyrene cones
Polystyrene cones protect small plants from the wind, cold temperatures and the weight of snow and freezing rain. It is best to purchase cones with holes in them, to allow air to circulate inside the cone for plants that rot easily, for south-facing locations (subject to more frequent temperature changes) and for plants susceptible to fungal diseases.
In all cases, the cones must be installed as late as possible after the first frost and removed in spring as soon as temperatures rise above 4 to 5 oC.
Jute canvas
Although it is not as effective as synthetic tarps, jute canvas serves essentially the same purpose. The main disadvantage to using jute is that it stays damp longer than synthetic fabric. For that reason, the jute must not be allowed to touch the leaves of conifers and plants that retain their leaves. The advantage to using jute is that it is a renewable resource.