Damping off

What you see

Seedlings that germinated well suddenly topple over. The stem is pinched, water-soaked and thread-thin right at soil level. Sometimes seedlings never emerge at all - they rot before they surface.

Conditions

Cold, wet, airless compost; sowing too thickly; overwatering; reused unwashed trays; and water from a butt rather than a tap.

Treatment

There is no saving a collapsed seedling. Remove them, stop watering, increase ventilation and light immediately, and let the surface dry between waterings.

Prevention

Sow thinly in fresh sterile compost, in clean trays, watered from below with clean water. Keep them bright, airy and no warmer than they need. A thin layer of vermiculite over the surface keeps the stem base dry.

Months: January, February, March, April, September, October

Plants

Tomato, Lettuce, Basil, Cabbage, Sweet pepper, Marrow / Courgette, Cosmos, Zinnia

Remedies

Bacillus subtilis biofungicide

The thing people get wrong

Almost every case traces back to kindness - warmer, wetter and more crowded than seedlings actually want. The fungi are in every compost; what decides the outcome is whether the surface ever dries. Sow half as thickly as feels right, water from the bottom, and give them more air than seems comfortable, and damping off simply stops happening.