How to properly protect thuja from frost: choosing materials and methods

Thuja is an evergreen plant widely used for landscaping parks, residential areas, and garden plots. The tree tolerates moisture deficits, strong winds, and other vagaries of the weather, but all of these can cause serious damage to its health and appearance. This versatile garden and park plant is very sensitive to ultraviolet radiation and adverse conditions that occur during the cooler months. To prevent damage, many gardeners prefer to cover the thuja for the winter.

Why cover thuja?

Thuja tolerates frost well, so it is only covered in regions where winter temperatures drop below minus 28°C. In the central zone and the Moscow region thuja shelter They are carried out not so much to protect against frost, but rather against winds, sunburn, snow accumulation and other unfavorable conditions that can cause damage to coniferous trees.

If the thuja is not covered for the winter, it can suffer serious damage:

• branches and even the trees themselves break;
• the vertical shape is lost - the thuja bends towards the ground;
• the bark is damaged due to frost cracks and sunburn;
• shoots and trunks are deformed;
• The needles turn yellow and dry out.

Insulating young arborvitaes is especially important. Otherwise, their shallow root system risks freezing if the winter is cold and snowy. However, arborvitaes of all ages require protection from ice and snow buildup.

To avoid exposing thujas to excessive environmental stress, it is recommended to plant them on the north or northeast side of buildings and structures. They thrive best in areas protected from the scorching sun and winds.

Mature arborvitaes don't need to be protected from frost, but they still need to be protected from snow, which can distort their shape. Large trees rarely break under the weight of snow, but they can easily be damaged by sunburn in early spring.

When to start covering work

There's no need to rush to cover your thujas. September and October are not suitable for this procedure. During this time, only a moisture-replenishing watering is necessary—this is essential for evergreens.

Thujas that are well watered in the fall tolerate frost better, as moisture is retained within the needles for a long time, preventing them from drying out during the winter. Moisture-recharging watering is a simple yet effective way to protect the tree from needle burn in the spring.

All covering work usually begins in November. Large and small arborvitaes are opened after the first snow has fallen and temperatures have settled at -5 to -7°C. These conditions occur at different times in each region, so when choosing a time to begin work, it's best to focus on the weather rather than the calendar.

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Covering materials

Various covering materials can be used to cover conifers. The main requirement is that they must be breathable. Thujas can be protected with non-woven materials such as agrofibre, spunbond, agroterm, and lutrasil. In addition to allowing air in, these materials also allow UV rays to pass through, so they cannot protect thujas from sunburn.

The most popular covering materials and their properties:

• Kraft paper. It's inexpensive, but doesn't provide reliable protection. It gets wet in the rain, and then, if frost hits, it freezes, losing its heat capacity.
• Burlap. This is an expensive material, especially if you have many arborvitaes to cover. For good air circulation, choose a loose burlap. Potato sacks are not suitable—the trees will suffocate in them.
• Gauze. It's inexpensive, but has the same drawbacks as kraft paper—it gets wet and freezes.
• Facade mesh. Suitable for material with a density of 42 g/m² or higher. It's cost-effective, provides air circulation, provides shade, but still allows the sun needed for tree growth. It's very durable. Recommended for mature arborvitaes.
• Spunbond. An inexpensive non-woven synthetic material. You can't simply wrap a tree in spunbond—it will suffocate it. The material is used only on the frame. Moreover, the needles must not touch the fabric.

It's recommended to cover the thuja with a light-colored material. White coverings reflect UV rays well, effectively protecting the needles from burning. If you're using black roofing felt for insulation, wrap it in a white cotton fabric, such as a sheet or duvet cover.

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Shelter options

Winter protection for thuja is complex – the covering must simultaneously protect it from frost, snow, UV rays, moisture evaporation, and wind. In practice, several covering methods are used, including tying the tree, covering it with covers, and constructing frames for the covering material.

Before covering the tree, it must be treated with antifungal agents. This treatment should be carried out one month before insulating it. The outside temperature should not drop below 12°C. Spraying is carried out with copper-containing products, such as Bordeaux mixture.

Circular binding

To prevent damage to the tree—branches breaking under the weight of snow, falling apart, or bending to the ground—the thuja is tied. The tree's branches are soft, so they droop easily under any load.

To tie the trees, you'll need a stepladder. If you don't have one, you can use an extendable pole with a hook on the end.

How to force a thuja:

1. The tree branches are gathered vertically. If any are broken, splints are applied. The arborvitaes are tied in a circle, securing the ends of the shoots with rope. Twine, string, soft fabric, or, in extreme cases, synthetic rope are used for tying.
2. The tree is tied so that the branches are not pressed against the trunk—air circulation must not be impeded. If the tree is tied too tightly, the needles on the trunk will rot.
3. The end of the rope is secured at the bottom of the trunk, and then twisted in a spiral - to the top and back.

Tying can be combined with insulation. White agrofibre is draped over the tree. The top is left open to allow light and air to penetrate, and then the tree is tied with twine. The tying is removed in early spring.

Covers

This is a simple and convenient way to cover trees. It's used when there's no time for more reliable insulation. When choosing a cover, consider the size of the tree. Small arborvitaes are easiest to cover. If you go to a store, you can find covers ranging in height from half a meter to 2.5 meters, and their widths can also vary.

The covers are made of non-woven materials of varying densities. They look like standard cone-shaped bags, but other designs are available. These covers protect trees from frosts down to -10°C.

A tree cover that wraps around the underside of the tree protects its bark from rodents. It's recommended to place the covers not on the tree itself, but on a special frame—one that's easy to make yourself.

Frames

Frames are typically made for small and medium-sized trees. They can be built by hand. Suitable building materials include: sticks or twigs, slats, plastic pipes, metal angles, and wire.

How to make the simplest frame for a thuja:

1. Drive 6-8 sticks around the tree.
2. Tie the sticks/twigs together above the treetop. If the tree is tall, use a stepladder to help you accomplish this task.
3. Tie the branches with rope so that they do not fall apart and do not touch the shelter.
4. Stretch the covering material over the prepared frame.

The result is a shelter. Its advantage is the sloping surface, which prevents snow from accumulating.

Ready-made frames are available at agricultural supply stores. If you don't want to build your own, you can purchase the required number of frames, choosing them according to the size of your trees.

When using frames, don't cover the tree with snow—it will rot the needles. Cover the frame only with high-quality material that meets breathability requirements. Blankets or plastic sheets should not be placed on the frame.

Sunscreen

Thujas are most often damaged by sunburn. This problem occurs in February and March. During this period, bright sunlight reflects off the still-unmelted snow, damaging the tree. Another cause of spring burn is a lack of water in the needles.

Young thujas have shallow, poorly developed roots. In winter, the soil freezes, preventing the tree from replenishing lost water. This causes moisture to evaporate from the needles, drying them out, and potentially killing individual parts of the plant. The exposed, sunny tip is usually affected.

To prevent the tree from burning under UV rays, a special “screen” is placed in front of it.

How to make a sun screen:

1. Drive the poles into the ground on the south side.
2. Stretch a sun protection material between the poles.
3. Place the screen at a small distance from the tree to avoid damaging the crown.
4. When the snow melts, the screen will be dismantled.

The screen is designed only to protect against UV rays, it has no other functions.

How does a potted thuja overwinter?

If arborvitaes are growing in pots, when cold weather arrives, they should be brought from outside into a cooler room, such as a basement or a glazed loggia/balcony. This solution will eliminate the need for covers, frames, and insulation.

The optimal temperature for overwintering potted arborvitaes is between +4°C and +10°C. The only material needed for overwintering potted arborvitaes is craft paper. Wrap each tree in it after watering it.

Mulching

In winter, it's important to protect not only the above-ground parts of trees, but also their roots. The best way to prevent roots from freezing is to mulch the soil around the tree trunk. Mulch retains moisture and heat in the soil.

How to properly mulch a thuja:

• mulch layer thickness – 10-15 cm;
• the mulch should be loose and well-aerated;
• You can mulch the soil with compost, sawdust, peat, straw, pine needles, crushed bark or pine cones.

It's recommended to cover the organic mulch or sawdust with spruce branches, which should be removed in the spring. This coniferous barrier is especially necessary for young arborvitaes, with their fragile roots, which are vulnerable to frost.

Thujas don't require much gardening, but with a little care, they'll become the centerpiece of your property. Protecting them from cold, sun, and wind will ensure these conifers won't burn or freeze, and will remain healthy and beautiful after the winter.