Guide
Protecting crops from frost
A few degrees of frost can destroy weeks of growth. Knowing which crops need cover and how to apply it quickly makes the difference.
Know your risk
Light frost is 0°C to -2°C and will damage tender crops like tomatoes, courgettes, and basil. Hard frost below -4°C can kill unprotected brassica seedlings and root crops left in the ground. Check overnight lows when a frost is forecast rather than the daytime temperature.
Fleece is the fastest fix
A single layer of horticultural fleece raises the temperature around plants by 2–3°C. Drape it loosely over crops and weigh the edges down with stones or pegs. It can stay on for several days without harming plants - light and moisture still get through.
Cloches and cold frames
Glass or plastic cloches trap heat more effectively than fleece. Place them over rows of seedlings before the frost arrives. Cold frames work well for hardening off plants or protecting low-growing crops through winter.
Pot plants in
Any tender crop in a pot should come inside or into an unheated greenhouse overnight when frost is forecast. Even a shed or garage offers enough protection for one night.
After a frost
Do not cut back blackened foliage immediately. Wait until temperatures stabilise and new growth shows what has survived. Cutting too early removes tissue that protects the plant crown from further cold. Water-soaked, collapsed growth is usually lost; wilted or discoloured but firm growth often recovers.