Hardening off is the process of gradually allowing plants started indoors to adapt to conditions outdoors at transplant time. Conditions outside are relative harsh – temperatures fluctuate, sunlight is more intense and unfiltered, and wind causes increased air movement. It’s a good idea to introduce seedlings to this environment slowly, over several days, before transplanting them to their permanent growing spots.

Bring your tray of seedlings outdoors, but maybe to a shady area on day one, and bring it back inside overnight. On day two, leave the tray in a protected, but sunnier location. On day three, leave the tray in that location and let it spend the night there. Finally transplant on day four or five.

Failure to harden plants off can lead to stress from too much sun, moisture stripped from the leaves by wind, or damaged stems and leaves just from exposure. Many plants will rebound, but it’s a sensible step to make the process gradual.