Why Cold Wind Hurts More Than Cold Alone

Most British conifers are perfectly hardy. A yew, a Scots pine or a leylandii will shrug off a fortnight of hard frost without complaint. What undoes them is wind. On a bright, still January day the mercury can sit at minus six and the foliage comes through unscathed, yet the same temperature with a stiff easterly behind it will turn a golden cypress brown in a matter of days.

The reason is straightforward. Conifer needles and scales are covered in a waxy layer that slows water loss, but it is not a sealed lid. Wind strips moisture from the leaf surface far faster than still air does, and in cold weather the roots cannot draw replacement water quickly enough from chilled or frozen ground. The result is desiccation: foliage scorched from the tips inward, often on the windward side only. Add the physical strain of a gusty site and the same wind that browns your branches will also rock the roots loose. Both problems are entirely preventable with a little work in late autumn.

Know Which Conifers Need Help First

Not every tree in the garden needs wrapping. Spend your effort where it earns the most.

• Newly planted specimens of any size — roots have not yet spread beyond the original rootball, so they both dry out and move easily.
• Golden and variegated conifers, such as goldcrest or golden cypress, which scorch more readily than their green counterparts.
• Columnar forms with dense, upright growth, which catch wind like a sail and can be split apart by snow sitting in the crotches.
• Dwarf and slow-growing varieties in containers, where the whole root system can freeze solid in a single hard night.
• Anything on an exposed, north-easterly or coastal site, where salt and wind arrive together.

Established, wind-hardened plants in a sheltered garden generally look after themselves. If a conifer has come through three winters unblemished, it has earned the right to be left alone.

Fleece, Netting and Windbreaks: Sheltering the Foliage

Horticultural fleece is the gardener's first line of defence, but how you fit it matters more than the fleece itself. A single layer of lightweight fleece gives perhaps two or three degrees of protection; a double layer is noticeably better. Crucially, it must not be pulled tight against the foliage. Build a loose cylinder around the plant instead, either by wrapping the fleece around canes pushed into the ground or by tying it off with twine so there is a cushion of trapped air between fabric and needles. Air is the insulation; the fleece simply holds it still.

Avoid plastic sheeting and bin bags. They seal in condensation, which then freezes against the foliage and does more damage than the wind ever would. If you need something more substantial than fleece, use fine-mesh windbreak netting on the windward side of the plant. A permeable barrier is far more effective than a solid one, because it slows the airflow rather than deflecting it into damaging eddies. A woven hurdle or a length of netting on three stout posts, set about a metre away from the tree, will do the job for years.

Staking and Anchoring Tall Specimens

Windrock is the quiet killer of young conifers. A tree that shifts a few centimetres in every gale tears fine roots and opens a gap in the soil that lets cold air straight down to the rootball. If a specimen is over about 1.5 metres, stake it.

Drive a sturdy timber stake at least 45 to 60 centimetres into firm ground, angling it towards the prevailing wind so the tree leans into the stake rather than away from it. Use a proper tree tie with a spacer block, or a length of wide, soft webbing looped in a figure of eight around trunk and stake, so nothing ever rubs the bark. Check ties monthly through winter: a tie that is comfortable in November can be biting into the trunk by February as the tree settles. For container-grown conifers, simply group the pots together in a sheltered corner and weight them down, or lay them on their sides if the site is truly brutal.

Watering and Mulching Before the Frost Bites

It sounds perverse to water a plant in November, but a conifer going into winter with dry soil around its roots is a conifer asking for scorch. If the autumn has been dry, give evergreens in the ground and in pots a thorough soak in late October or early November, before the first hard frosts arrive. Water slowly and deeply, ideally in the morning, and stop altogether once the ground is frozen — watering a frozen rootball only creates a block of ice.

Then mulch. A ring of well-rotted compost or bark chippings, five to eight centimetres deep, spread over the root zone but kept clear of the trunk, moderates soil temperature and slows moisture loss. For pots, stand them on feet or bricks to keep drainage holes clear of standing water, and wrap the container itself in hessian or bubble wrap, leaving the top of the compost open to the rain. Frozen roots cannot replace lost moisture, and insulation is what buys them time.

Check, Repair and Tidy in Late Winter

Fleece and netting should stay in place until the risk of hard frost has passed, which in most of the UK means late March, and into April in the north and on higher ground. Do not unwrap early because of one mild week; a sharp return of easterlies is exactly the sort of weather that catches people out.

During the winter months, knock heavy snow off columnar conifers with a soft broom before it can bend or snap branches. Never pile salted grit or shoveled snow onto beds beneath conifers, as the salt will burn foliage and damage roots. When you do unwrap, look for browned patches; in most cases new growth will cover them by midsummer, and only badly damaged shoots need trimming back to a healthy side bud in late spring. A little preparation now means you can spend next winter looking out of the window rather than worrying about what is happening out there.