Damping Off of Seedling Plants
What causes damping off?
It’s caused by soil-borne fungi that thrive in:
Seedlings usually die before or just after sprouting, often suddenly.
How to prevent damping off (step by step)
1. Use clean containers
2. Use sterile seed-starting mix
3. Don’t overwater
4. Give seedlings air circulation
5. Provide warmth (but not cold + wet)
6. Don’t overcrowd seedlings
7. Light is essential
Quick prevention checklist ✅
- Too much moisture
- Poor air circulation
- Cool temperatures
- Dirty containers or old soil
- Wash reused pots and trays with hot soapy water
- Disinfect with a 10% bleach solution (1 part bleach: 9 parts water)
- Make sure containers have drainage holes
- Do not use garden soil
- Use fresh, bagged seed-starting mix
- These mixes drain well and contain fewer pathogens
- Soil should be moist, never soggy
- Water from the bottom when possible
- Empty standing water from trays
- Let the surface dry slightly between waterings
- Use a small fan on low nearby or a room with forced-air heating/cooling
- Gentle movement strengthens stems
- Avoid stagnant, humid air
- Most seeds prefer 65–75°F (18–24°C)
- Cold, wet soil encourages fungus
- Remove humidity domes as soon as seeds sprout
- Space seeds properly
- Thin extras early (snip with scissors)
- Crowding traps moisture and limits airflow
- Provide 12–16 hours of bright light
- Keep grow lights close (2–3 inches above plants)
- Strong seedlings resist disease better
- Clean containers
- Fresh seed-starting mix
- Moist, not wet soil
- Airflow + light
- Warm soil
- Thin seedlings