Once the risk of frost has passed, it is time for your spring-sown seedlings and half-hardy plants to be acclimatised to growing outside in a process known as ‘hardening off’. This is needed because seeds sown indoors or in a greenhouse, require a little time to adjust to cooler temperatures, lower humidity, and increased air movement before they are planted outdoors.

By gradually acclimatising tender plants to the outdoors over the course of a few weeks, the plant’s leaf structure will thicken and increase in waxiness, ensuring sturdy growth.

How to Harden Off

For a few weeks, place plants outside in a sheltered spot, ideally in front of a south-facing wall or hedge, during the day then bring indoors at night. Alternatively, place them in a cold frame, opening the lid during the day and closing it at night.

Both of these options give plants short periods of exposure to outside temperatures, allowing them to become accustomed to the conditions.

Gradually increase the exposure, leaving them outside but covered with a layer of fleece after a few weeks.

Finally, it will be time to keep them outside uncovered before planting out strong, sturdy specimens.

By following these simple steps, you can guarantee the best possible start in life for your prized plants.