From seed tray to garden
Harden off seedlings before transplant day
A transplant date marks a move into the garden. Before that move, seedlings raised under cover need time to adjust to outdoor light, wind and temperature changes.
Reviewed Oct 28, 2026
Leave time before the move
University of Minnesota Extension describes a gradual two-week transition. The RHS gives about two to three weeks for tender plants, with timing affected by their previous growing conditions. These ranges are planning references, not a promise that every seedling will be ready on the same day.
Introduce outdoor conditions gradually
Minnesota Extension recommends beginning with a few sheltered hours outdoors in afternoon shade. Bring seedlings back inside before temperatures drop at night. Increase the time outdoors and the amount of direct sun gradually as the plants adjust. Avoid treating a warm afternoon as permission to leave tender plants out through a cold night.
Check the forecast again
The RHS warns that hardening off does not make frost-sensitive plants frost-hardy. Your average last-frost date is a planning reference; it is not a forecast for transplant day. If cold or exposed conditions persist, postpone the move and keep caring for the plants under suitable protection.
Keep the preparation date with your transplant task
Open My Plan and edit the transplant task’s notes. Write down the date you intend to begin hardening off and the conditions you want to check. Notes stay with that task, but they do not create a separate calendar reminder. If you move transplant day, review the preparation date yourself as well.
- Choose a realistic transplant window using your packet and local guidance.
- Record a preparation date roughly two weeks earlier in the task notes, adjusting for the plants and conditions.
- Use a separate reminder in your calendar if you need a notification, and update it when your plan changes.