How Do I Protect the Garden from Late Spring Frosts After I Have Planted Out?

Late spring frosts are among the most frustrating and damaging events in the kitchen garden. You have nurtured plants from seed through weeks of indoor raising and careful hardening off, planted them out in what felt like settled spring weather — and then a late cold snap arrives. Knowing how to predict, prepare for, and respond to late spring frosts saves the season.

When Late Spring Frosts Typically Occur

In the UK, late spring frosts can occur any time up to late May in most regions, and into June in cold upland areas of Scotland and northern England. The average last frost date gives a 50% probability — meaning half of all years see frost after that date. Ice saints days (11–14 May in European tradition) are a rough guide to a commonly frosty period in continental Europe. Climate variability means these events are irregular: a warm April followed by a cold May snap is entirely plausible. Never relax frost vigilance completely until night temperatures are consistently above 7 °C.

Forecasting Tools That Help

Modern five-day forecasts are highly accurate. Check minimum overnight temperatures each day during April and May. Any forecast minimum below 4 °C in your area should trigger preparation — surface temperatures where plants sit often run 1–2 °C colder than the official air-temperature forecast. The Met Office frost probability maps (UK) and equivalent national services are useful for regional trends. A personal minimum thermometer in the garden gives you actual data about your specific site over time.

Protecting Planted-Out Tender Crops

If you have tender crops already in the ground and frost is forecast, cover them the same evening. Do not wait until the following morning — by then the damage is done. Fleece draped over plants and weighted at the edges is the fastest response. For tomatoes and courgettes in individual spots, place bell cloches or improvised bottle covers. For entire beds of recently transplanted seedlings, lay fleece across the whole bed. Remove covers the following morning once temperatures are safely above 2–3 °C.

What to Do When You Cannot Cover Everything

Prioritise based on frost sensitivity. Tomatoes, peppers, basil, cucumbers, and courgettes die at any frost — cover these first. Runner beans and French beans are also frost-killed — cover them next. Brassica transplants, leeks, beetroot, and lettuce can tolerate light frost (down to −2 °C) — leave these uncovered to free up your limited fleece for the truly tender crops. An organised triage based on plant vulnerability maximises the protection you can deliver with limited time and materials.

Recovering from a Late Frost Hit

If some plants are frosted, do not discard them immediately. Wilted, water-soaked foliage on the morning after frost is not always fatal. Keep the plants in place, do not water, and assess after 48–72 hours. Tender annual vegetables like courgettes and tomatoes with completely collapsed top growth are probably lost — resow or replace. But if the growing point at the stem tip shows any green and is firm to the touch, the plant may recover. Shade cloth reduces sun intensity while the plant recovers from initial stress.