How to Harden Off Seedlings Before Transplanting

Gradually expose indoor-grown seedlings to outdoor conditions over 7-10 days by placing them outside for increasing periods, starting with 1-2 hours in shade and building up to full sun exposure.

1. Begin in Sheltered Shade. Place your seedlings outside in a shaded, wind-protected area for 1-2 hours on the first day. Choose a spot like under a covered porch or near a building where they get indirect light but no direct sun or wind. Bring them back inside afterward.
2. Stretch Their Outside Hours. Each day, extend the time outdoors by 1-2 hours while keeping seedlings in the same protected location. By day 3 or 4, they should be outside for 4-6 hours. Watch for signs of stress like wilting, yellowing, or drooping leaves.
3. Add Gentle Morning Light. Around day 4-5, move seedlings to a location where they receive gentle morning sun for 1-2 hours, then return them to shade. Morning sun is less intense than afternoon sun and helps plants adjust gradually to direct light.
4. Build Sun Tolerance Daily. Add 1-2 hours of direct sun exposure each day while continuing to extend total outdoor time. By day 7, seedlings should handle 4-6 hours of direct sun. Always monitor for wilting and provide water if soil feels dry.
5. Trial Run Under Stars. On day 8-9, if nighttime temperatures will stay above 50°F, leave hardy seedlings outside overnight in their containers. Bring tender plants like tomatoes and peppers inside if temperatures drop below 55°F.
6. Ready for the Garden. By day 10, properly hardened seedlings should tolerate full sun, wind, and temperature fluctuations. They can now be transplanted into your garden. Choose an overcast day or evening for transplanting to reduce shock.