Damping Off: Why Healthy Seedlings Suddenly Collapse
A seedling that looked perfect yesterday and is lying flat today, with a stem that has gone thin and brown right at the soil line, has damping off. It is a fungal problem driven by conditions, not bad luck.
What causes it
Soil-borne fungi thrive in cool, saturated, stagnant conditions. Constantly wet surface soil plus no air movement plus temperatures under 70°F is the exact recipe.
Stopping it now
Remove the affected seedling and the soil around it. Stop watering until the top inch is dry. Get a small clip fan moving air across the soil surface — not blasting the seedlings, just stirring the air. Raise temps toward 75°F.
Preventing it next time
Use clean containers and fresh, well-draining medium. Water in a ring rather than soaking the whole surface. Vent humidity domes daily. Keep gentle air movement from day one.
- Fresh, sterile starting medium
- Surface allowed to dry between waterings
- Constant gentle airflow
- Temperatures 72-78°F
Frequently asked questions
- Can a seedling recover from damping off?
- Once the stem has pinched at the base, no. Focus on protecting the remaining seedlings by fixing airflow and moisture.
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