Preparing Your Garden For A Sudden Cold Snap

Act Before Dusk: Moving The Tender Pots

A sudden cold snap rarely gives much warning. The forecast shifts from a soft autumn evening to a hard frost by dawn, and anything in a container is right at the front of the queue for damage. Pots freeze from the outside in, and the roots inside have nowhere to retreat. Do the heavy lifting in the afternoon, while the light holds and your fingers still work.

• Move pelargoniums, citrus, olives, bays, agapanthus and tree ferns into a greenhouse, porch or unheated conservatory. Even a shed will do at a push, provided it stays dry.
• Group the pots you can't move close together against a south-facing house wall. Clustering traps warmth between the containers and cuts the wind.
• Stand every pot on feet, bricks or a folded newspaper so the drainage hole isn't sitting in freezing water. Waterlogged roots in a cold pot rot faster than dry ones.
• Wrap terracotta and glazed ceramic pots with bubble wrap or an old blanket, secured with twine. A terracotta pot full of damp compost will otherwise crack clean open.

If a plant is simply too heavy to shift, wrap the pot and the top growth in a double layer of horticultural fleece and tie it off loosely at the base. Remove the fleece on mild days so the plant can breathe.

Shelter What Has To Stay In The Ground

Border plants are generally tougher than pots, but a sharp, dry frost after a wet spell catches out even the stalwarts. Water thoroughly the morning before the cold arrives if the ground is dry — damp soil holds warmth far better than dusty soil, and well-hydrated plants cope better with freezing.

• Lay fleece over tender border subjects, weighting the edges with stones rather than pegging it tight. Floating fleece is warmer than stretched fleece.
• Use cloches over salads, chard and young broad beans, and ventilate them during the day to avoid damping off.
• Mulch crowns of penstemons, salvias and hardy fuchsias with a dry layer of compost, bark or bracken, but keep it clear of the stems.
• Lift dahlias, cannas and gladioli if the ground is likely to freeze solid, and store the tubers somewhere frost-free and dry in barely moist compost.

Resist the urge to cut back frosted herbaceous growth just yet. Those dead stems and seedheads insulate the crown beneath and feed the birds besides.

Harvest And Store Before The Frost Bites

The last of the tender crops won't survive a hard night, so bring them in while they're still sound. Anything with a bruise or a split will rot in store and take its neighbours with it.

• Cut and cure squash, pumpkins and marrows somewhere warm and airy for a fortnight before moving them to a cool shelf.
• Lift maincrop potatoes and let them dry before bagging. Any still in the ground should be earthed up deeply and covered with straw.
• Pick green tomatoes and ripen them indoors on a windowsill or in a paper-lined drawer with a ripe banana.
• Clear runner beans, courgettes and sweetcorn, which all turn to mush at the first real frost.

Leave parsnips, leeks, kale and Brussels sprouts where they are — they shrug off the cold and taste sweeter for it. Carrots can stay put under a thick straw mulch, though slugs will happily find them first. Bring a parsley plant indoors before it blackens.

Get The Greenhouse Working Harder

An unheated greenhouse gives you a useful few degrees of protection, but only if you help it. Line the inside of the glass with bubble wrap insulation, leaving the vents and the door clear, and make sure the bubble side faces inwards.

• Test the heater before you need it. An electric fan heater on a thermostat is the most reliable option; paraffin adds moisture and needs ventilation.
• Check for cracked panes, gaps around the frame and a door that no longer closes flush. A draught will undo everything else you do.
• Wash the glass and remove any summer shading so the plants catch every hour of low winter light.
• Water sparingly in the morning rather than the evening, and never leave foliage wet overnight. Damp cold air and still conditions are a recipe for botrytis.

Open the vents for an hour on bright, still days — trapped humid air does more damage than a brief chill.

Help The Wildlife Through It

A cold snap is hard on everything that shares your garden, and small kindnesses make a real difference. Keep feeders topped up with high-fat food, and put out a shallow dish of fresh water, checking it hasn't frozen over each morning.

• If your pond ices over, float a ball on the surface or melt a hole with a warm pan. Never smash the ice — the shock can kill frogs and newts resting below.
• Leave a messy corner: log piles, leaf litter and undisturbed seedheads shelter hedgehogs, ladybirds and lacewings.
• Delay cutting back ivy and berried shrubs until late winter, when the food they hold matters most.
• Check any bonfire heap before lighting it, and keep an eye on drains and water butts where small mammals can become trapped.

After The Thaw

Once temperatures climb back above freezing, walk the garden before you do anything else. Water pots that have dried out under cover, and check whether fleece has been flattened onto foliage. Blackened leaves and mushy stems can be trimmed away, but leave woody plants alone until spring — it's often clearer then which stems are truly dead, and pruning too early exposes fresh cuts to the next frost. Firm back any plants lifted by the freeze-thaw cycle, and reward yourself with a cup of tea. Your garden will thank you for the afternoon's work.