How to harden off seedlings
Seedlings grown indoors need about a week of short, lengthening visits outside before they live there. Skipping it can scorch or stunt them.
Words to know
- Hardening off:
- Getting indoor seedlings used to sun, wind and cooler nights, a little more each day.
How to do it
- Start 7–10 days before you plan to plant them in the garden.
- Days 1–2: set them outside in shade, out of the wind, for 1–2 hours.
- Days 3–5: a few hours outside, with some morning sun.
- Days 6–8: most of the day outside, including afternoon sun.
- Last days: leave them out overnight if nights stay above 50°F (45°F for lettuce and the cabbage family).
- Check the pots every day — they dry out much faster outside.
Avoid
- ✕ Full afternoon sun on the first day.
- ✕ Leaving them out on a cold or windy night early on.
Based on standard guidance from U.S. university extension services, including Cornell, the University of Minnesota and Oregon State.