Damping Off Prevention
Technique
Damping off is a common seedling problem that causes stems to rot at the soil line or seedlings to collapse soon after emergence. Prevention depends on clean conditions and careful moisture management.
How to do it
Use clean containers and fresh seed starting mix rather than reusing old potting media. Sow seeds thinly so air can move between seedlings, and provide bright light after germination. Water enough to keep the mix moist but not waterlogged, and let the surface dry slightly between waterings when appropriate. Improve airflow with spacing and gentle ventilation, and remove weak or fallen seedlings promptly.
Timing
Focus on prevention from sowing through the first few weeks after germination, when seedlings are most vulnerable. Problems are more likely when light is low, temperatures are cool, and the growing medium stays too wet. Early attention is more effective than trying to correct severe losses later.
Tips
Avoid overcrowding flats or covering trays in a way that traps excess moisture for too long after seedlings emerge. Bottom watering can help keep stems and the surface drier. Good light and steady airflow are simple, effective safeguards.
General guidance for US gardens. Timing depends on your local frost dates and hardiness zone. Page updated Aug 4, 2026.