Hardening Off Carnation Seedlings: What It Means and When to Do It

“Hardening off” means gradually acclimating indoor-grown seedlings to outdoor conditions—sun, wind, temperature swings—over 7–10 days.

Process

1. Wait until after the last frost date (late April in Louisville, KY).
2. Place seedlings in a shaded, sheltered outdoor spot for a few hours daily, increasing exposure each day.
3. After 7–10 days, plant in full sun.

Indoor Growing Note

Carnations need 8+ hours of direct sun; a windowsill rarely provides enough. A greenhouse or supplemental grow lights are required for indoor success.