Water the garden before a frost, not after
When a frost is forecast, most gardeners reach for fleece and forget the hose. But wet soil survives a cold night far better than dry soil, and the roots you're trying to protect are the ones that ran out of water first. One good soak before the temperature drops does more for tender plants, pots and new plantings than any cover alone. Here's how to time it.
Why damp soil freezes less hard than dry soil
Water holds heat far better than air-filled, dry ground. A moist bed stores warmth through the day and gives it back overnight, so the soil around the roots stays a degree or two warmer and the frost bites less deeply. Dry, dusty soil has nothing to hold heat with — it chills fast, and the fine new roots at the edge of the root ball are the first to go.
Soak a day or two ahead, in the morning
Give beds, shrubs and pots a slow, deep soak 24–48 hours before the frost is due, so the moisture is down in the root zone rather than sitting on the surface. Water in the morning so leaves and crowns have time to dry before nightfall — a plant going into a cold, still night with wet foliage is asking for blackened growth and grey mould.
Pots are the ones that need it most
A pot freezes right through, and a dry one freezes harder and faster than a moist one. Check containers before a cold snap — lift them, or push a finger in an inch down — and water anything that's gone light. Group pots together, move them against a wall or under cover, and keep watering right up until the ground stays frozen. Terracotta is the exception: soak it, then let it drain, because water trapped in the wall of a pot is what splits it.
Then insulate, drain, and know when to stop
After the soak, a 5–8 cm layer of compost or leaf mould over the root zone holds that moisture in and buffers the temperature swings. Empty the saucers — standing water freezes and cracks pots and fittings. Once the ground is genuinely frozen or waterlogged and staying that way, stop watering: the roots can't take it up, and you're only inviting rot. Evergreens and new hedging still get checked monthly through dry, frosty spells.
The takeaway
Before a frost, water deeply the day or two before and in the morning — damp soil holds heat, dry soil freezes hard. Pots need it most, then mulch, drain the saucers, and stop once the ground stays frozen.
Frost protection & winter kit