Damping Off: Why Healthy Seedlings Suddenly Collapse
By The Budometry TeamPublished Updated
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.
Part of our pillar guide: How to Grow Cannabis Indoors: The Complete Guide
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.
The full guide on this topic
How to Grow Cannabis Indoors: The Complete Guide
The full indoor grow process from a 15-hour dark seed soak to a jarred cure, with the tent, light, airflow and feeding decisions explained in order.
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