Disease

Damping-off

Seedlings that topple over with a thin, pinched stem at the soil line.

What you'll see

• Seeds rot in the mix and never come up.
• Seedlings topple over with a thin, water-soaked or brown stem at the soil line.
• Seedlings collapse in patches, sometimes covered in white fungal growth.

Why it happens

Soil-borne fungi and water molds attack young seedlings, worst in cold, wet, crowded conditions.

How to fix it

1. Remove collapsed seedlings and the mix around them; they can't be saved.
2. Let the surface dry between waterings and improve the air flow.
3. Thin crowded seedlings, or sow again in fresh mix in clean trays.

Keep it from coming back

• Use new or well-cleaned trays and fresh seed-starting mix.
• Sow thinly into warm mix, about 65 to 70°F (18 to 21°C).
• Water lightly rather than soaking the trays.

Read more

• Bottom watering: how and when
• Starting seeds indoors

Sources

• UC IPM: Damping-off diseases in the garden
• RHS: Damping off

General guidance, not a diagnosis. For valuable, edible or outdoor crops, check with a local extension service or plant expert. Use any product exactly as its label says, and keep children and pets away while it dries.