Damping Off
A collective term for seedling collapse caused by soil fungi and water moulds (Pythium, Fusarium, Rhizoctonia) that attack seeds and seedlings at or below the soil surface. It is the most common cause of seedling death in indoor propagation and is caused almost entirely by overwatering and poor airflow — both of which are fully preventable.
Symptoms to Look For
- Seedlings collapsing suddenly and lying flat, appearing pinched or constricted at the soil surface
- The collapsed stem is water-soaked, brown, or shrunken at the point of failure — the stem below is fine
- Previously healthy seedlings falling over overnight with no recovery
- White or grey mould on the soil surface around affected seedlings
- Poor germination rates in trays that were kept too wet
Affected Plants
Organic Solutions
Improve Air Circulation
Introduce a small fan to your propagation space, set on the lowest setting. Even intermittent air movement dramatically reduces the surface humidity that damping-off pathogens require. 30 minutes of air movement per day reduces incidence significantly.
Water from Below
Place seed trays in a shallow tray of water and allow compost to absorb moisture from below. This keeps the soil surface drier and deprives pathogens of the surface moisture they need to spread. Allow the surface to partially dry between waterings.
Use Fresh, Sterile Seed Compost
Always use fresh, purpose-made seed-starting compost rather than reused potting mix or garden soil. Damping-off pathogens are abundant in non-sterile growing media. Start every new batch of seedlings in a fresh, sterile medium.
Chamomile Tea Drench
Brew a strong chamomile tea, cool it, and use it to water seedlings once a week. Chamomile contains trans-farnesol and other compounds with documented antifungal activity against Pythium and Botrytis species.
Prevention
- Never overwater seedlings — this is the single most impactful preventive measure for damping off
- Sow seeds thinly so seedlings are not crowded; dense planting traps moisture and reduces essential airflow around stems
- Sterilise reused trays and pots in a 10% bleach solution, rinse well, and dry before use — pathogens persist on plastic surfaces between sowings
Garden, by Willowbottom recommends only organic, wildlife-friendly solutions. No synthetic pesticides, no harmful chemicals — ever.