When to Plant Out Tender Crops

Plant out when the crop’s temperature needs are met, the risk of damaging cold has passed and the plants have been hardened off. A warm day or a date on the calendar is not enough on its own.

By Simon Adams · Updated 25 October 2026

Check the crop, not one universal temperature

Tomatoes, cucumbers, peppers, courgettes, squash and tender beans do not all respond identically to cool conditions. Frost-free weather can still be too cold for strong growth. Check the individual crop guide and the requirements of the variety you are growing.

As useful examples, RHS guidance says tomatoes do better with nights above 10°C. Its cucumber guide recommends planting only when local temperatures are reliably above 12°C. These are decision aids, not promises that a plant cannot be damaged: consider exposure, soil conditions and the forecast together.

Harden plants off gradually

Indoor and greenhouse-raised plants need to adjust to outdoor light, moving air and cooler conditions. Start in a sheltered position for short daytime periods, increasing exposure gradually. Bring tender plants back under cover when cold is expected.

Allow roughly two to three weeks, adapting the process to the weather and how the plants respond. Do not leave soft young plants in strong wind or intense sun simply to keep to a schedule. Hardening off improves adjustment; it does not make a frost-sensitive crop hardy.

Our seedling care and hardening-off guide explains the process in more detail.

Check several nights and your own growing space

Read the forecast minimum temperatures for the coming nights, rather than relying on today’s maximum. Keep checking as planting approaches. A last-frost average describes past conditions; it cannot rule out a cold night this year.

Use a garden thermometer too. Low areas and exposed positions can differ from the forecast location. Check that the soil is suitably warm and workable. An unheated greenhouse needs its own temperature checks: being under cover does not automatically make early planting safe.

Make the planting day gentle

Choose calm conditions where possible. Water plants before removing them from their pots, minimise root disturbance and water them into their final position. Follow crop-specific planting depths. For cucumbers and other cucurbits, avoid burying the stem base or leaving it sitting in wet compost.

If cold returns, delay planting and keep plants in adequate light with room for their roots. Have suitable temporary protection ready, while recognising that covers offer limited protection.

How I use Your Growing Companion

In my own garden, the app’s local temperature information helped me choose when to plant the cucumbers out, rather than repeating the approach I had used in earlier years without the app. It gave me useful information for that decision.

Your Growing Companion’s free sowing calendar and frost/cold alerts can help you plan and notice a change in conditions. Combine that information with the needs of the crop, the forecast and what you observe in your own garden.