Across Britain and the US, the same winter reflex quietly wipes out pots of citrus, oleander and tender shrubs: a protective gesture that backfires spectacularly.
The winter panic that kills more shrubs than frost
Cold weather triggers a very human urge: rush outside, grab anything waterproof, and cover plants before they “catch” the frost. It feels logical. It feels caring. It is also the exact moment many gardeners sign a death warrant for their shrubs.
Instead of specialist materials, people grab what’s lying around: old tarps, bin bags, leftover bubble wrap from a house move. The thinking is simple: if it keeps out wind and rain, it must keep the plant safe too.
In most gardens, the real winter enemy isn’t the cold itself, but the airtight plastic wrapped tightly around living plants.
Plants, even in deep winter, are not pieces of furniture. They breathe, release moisture, and react to light and temperature. Smothering them in airtight, non‑breathable material turns a simple cold spell into a lethal trap.
The plastic trap in the shed
Ask around a typical street and you’ll hear the same list of “protectors”:
- Blue plastic tarpaulins
- Black bin bags pulled over shrubs
- Sheets of bubble wrap taped around pots
- Offcuts of polythene from DIY projects
These products are designed for storage, transport and building work, not for living organisms. They are strong and waterproof, which feels reassuring in a storm. Yet this very waterproof quality is what causes the damage.
Under plastic, there is no real air exchange. Moisture from the soil and leaves cannot escape. The plant is locked inside a tiny, humid bubble. Within a day or two, the conditions under that “protective” cover bear little resemblance to natural winter air.
A frozen sauna around your shrubs
Even in January, plants lose water through their leaves and stems. Soil evaporates moisture too. Under a breathable cover, that vapour drifts away. Under plastic or bubble wrap, it has nowhere to go.
Droplets build up inside the cover, coat the foliage and run down stems. It feels cosy when you lift the cover with your hand: damp, mild, almost tropical. Then night falls.
Stagnant humidity plus sub-zero temperatures create the perfect recipe for leaves to burn, blacken and collapse overnight.
When temperatures plunge, all that trapped water freezes against the plant. Ice conducts cold much more effectively than dry air. Instead of a soft insulation layer, the shrub is now in direct contact with a thin shell of ice. Frost damage is suddenly more extreme than if the plant had stayed uncovered.
Leaves stick to the inside of the plastic, freeze onto it, and suffer deep tissue damage. By spring, they fall off in clumps, and many evergreen shrubs never recover.
The temperature yo-yo that confuses plants
Plastic creates a second, invisible problem: violent temperature swings. On a bright winter day, the sun hits that plastic sheet or bubble wrap and acts like a greenhouse panel.
Inside the cover, the air can quickly jump to 10–15°C while the garden around is barely above freezing. That feels pleasant when you peek under the sheet, but the plant reads it as a signal: “Spring is coming.”
Warm afternoons under plastic, followed by sharp frosts at night, are far more damaging than a steady cold spell.
When temperatures rise, sap starts to move gently again. Buds may begin to swell, especially on Mediterranean or citrus plants. Then, as soon as the sun goes, the same plastic lets the heat vanish almost instantly. The plant crashes from a mild “spring” to a hard frost in a matter of hours.
Fresh, water‑rich tissues cannot cope with that shock. Cells burst, bark splits, and young buds blacken. From the outside, the shrub still looks “wrapped and safe”, but the damage happens under the cover, slowly and silently.
When protection turns into a mushroom farm
Those that escape the worst of the cold face another threat: fungus. Under an airtight cover, wet leaves and still air provide ideal conditions for rot.
Gardeners often only see the scale of the problem when they finally remove the plastic in March. The sight is familiar to plant clinics:
- Brown, limp leaves coated in grey or white mould
- Blackened stems that snap rather than bend
- A musty smell rising from the plant and soil
Pathogens such as grey mould (Botrytis) thrive in this kind of microclimate. Some shrubs, like lavender, olives and many citrus varieties, are far more threatened by this winter damp than by brief, dry frost.
A plant can often come back from one harsh freeze. Months of slow, moist decay under plastic usually end in a shovel and a bin.
The materials that really protect your plants
A different mindset makes a big difference: rather than asking “What keeps out water?” the better question is “What lets the plant breathe while softening the cold?”
According to psychology, life really starts to improve when you stop chasing other people’s approval
Breathable fleece and horticultural fabric
Lightweight winter fleece, often sold as plant protection fabric, is made to be breathable. Air and water vapour can pass through, but wind and harsh temperature swings are softened.
Used correctly, it can:
- Raise the temperature by a few degrees around the plant
- Reduce wind chill on leaves and stems
- Allow light through for evergreen foliage
- Prevent condensation building up on leaves
It functions less like a plastic raincoat, more like a woollen jumper: it insulates without sealing.
Natural, low-tech options that work
For gardeners who prefer low‑waste solutions, simple materials can perform surprisingly well. Burlap sacks, jute fabric, straw and dry leaves all offer insulation while staying breathable.
| Material | Best use | Main benefit |
|---|---|---|
| Jute or burlap | Wrapping shrubs, covering foliage lightly | Breathable, reusable, blends into the garden |
| Straw | Around pots and over crowns of perennials | Good root insulation, cheap and natural |
| Dry leaves | Mulch at the base of plants | Protects roots, improves soil as it breaks down |
A thick collar of straw or leaves around a pot, held in place with chicken wire or a crate, protects the roots without sealing off the plant above ground.
How to wrap a shrub without suffocating it
Even the right fabric can fail if it is used badly. The way you install it matters just as much as the material itself.
Think of building a mini tent rather than pulling on a hood. A simple method:
- Push three or four stakes into the soil around the shrub
- Form a loose frame that stands slightly taller than the plant
- Drape fleece or jute over the structure so it doesn’t press on the foliage
- Tie it loosely at the bottom, without strangling the base of the stem
This creates a thin cushion of air between the plant and the fabric, which adds insulation and reduces rubbing damage on leaves in windy weather.
A good winter wrap should never squeeze the trunk or crown; it should sit around the plant, not on it.
Plants also benefit from regular checks. During mild spells, opening the cover during the day lets the air dry out and prevents fungal issues building up. That five‑minute walk around the garden after a week of rain can save entire collections of potted shrubs.
When plastic still has a place – and when it doesn’t
Not all plastic is automatically banned from winter gardening. The key lies in how and where it is used.
Short-term plastic covers can work in two specific situations:
- Ahead of a single, sharp frost: a loose sheet thrown over plants for one night, removed in the morning.
- To keep pots dry at the base: bubble wrap around containers only, leaving foliage fully exposed to air.
What causes the trouble is long-term, airtight wrapping of the entire plant, especially for weeks at a time. That is the scenario that led to one neighbour’s heartbreaking row of dead shrubs in early spring.
Reading the signs: is your plant suffocating?
Gardeners can often spot warning signs long before a plant dies. A few clues that a winter cover is doing more harm than good:
- Leaves feel clammy or slimy when you touch them under the cover
- Condensation drips from the inside of the fabric every time you lift it
- Mouldy smell when you open the protection
- Yellowing or browning leaves appearing in mid‑winter, not just after frost
At the first hint of these symptoms, lifting, loosening or changing the material can still save the plant before serious rot sets in.
Why tender plants react so badly to bad wrapping
Many of the shrubs people most want to save – olives, oleanders, bay, citrus, rosemary – come from warmer climates with dry winters. They are not adapted to sitting in cold, wet air for weeks.
For these species, three things are particularly risky:
- Cold plus high humidity around the leaves
- Repeated freeze–thaw cycles on waterlogged stems
- Poor air flow around dense, evergreen foliage
Understanding that risk helps choose the right strategy. Often, moving a pot to the shelter of a wall, combining a thick mulch on the roots with a light, breathable cover on top, gives far better survival rates than the familiar black bin bag pulled over in a rush.
Good winter protection works with plant biology, not against it. The goal is steadier, slightly kinder conditions, not a sealed bubble.
For anyone with a balcony full of tubs or a small back garden, rethinking that “instinctive” use of plastic can be the difference between a thriving spring display and a silent, bare corner where last year’s favourites once stood.
