Photo: Howard F. Schwartz, Colorado State University, Bugwood.org

Damping Off

Seedlings topple over with a thin, dark, water-soaked pinch right at the soil line while the top of the plant still looks green. Seeds that rot before they emerge are the same problem, and the pinched stem is what separates it from drying out, which withers the whole seedling evenly.

Disease15 plants we cover get damping offmostly annuals

Disease checklist

Four things to look for. If most of them match what you are holding, you are in the right place.

Stem pinched thin and dark exactly at the soil surface
Seedling falls flat while its leaves are still green
Bare patches in a tray where seeds never came up
Sometimes a fine white or grey web on the mix surface

What gets rid of it

Gentlest option first. For most backyard cases the first one is enough, so try these in order and stop as soon as it works. If you do spray something, the product label tells you how — please read the notice further down.

1Use fresh sterile seed-starting mix
Start seeds in new bagged seed mix, never garden soil or last year's leftover potting compost.
seed starting mix sterileTry this first
2Disinfect reused trays and pots
Scrub off old soil then soak containers in a dilute bleach solution and rinse before filling.
seed starting trays with drainage
3Water from below and let the surface dry
Set trays in a shallow bath until the mix wicks moisture, then drain, so the surface is not constantly wet.
bottom watering seed tray
4Run a small fan over the seedlings
Gentle air movement dries the surface and thickens stems; keep the trays around 70F rather than cold and damp.
small clip on fan for seedlings
5Take the humidity dome off at emergence
Remove the cover as soon as the first seedlings break through instead of leaving it on for the whole tray.
seed starting humidity dome
6Sow thinly and hold off the fertiliser
Crowded trays stay wet, and feeding before true leaves appear pushes soft growth the fungi attack.

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Which plants get damping off

Every plant we cover that gets damping off, grouped by type — tap any one to open its page. A note beside a plant came from that plant’s own entry, because the same disease can be a minor nuisance on one plant and a serious problem on another. Plenty of plants we do not cover get it too.

annuals15

Plant families hit hardest

Related plants often share the same problems, so if one plant in a family has it, check the others. The largest group here is Solanaceae, with 4 of the 15 affected plants.

Solanaceae4 plants
Asteraceae3 plants
Amaranthaceae2 plants
Brassicaceae2 plants

When to treat

Once a seedling has flopped it cannot be saved and there is no home treatment that reverses it, so everything useful happens before sowing: clean containers, fresh sterile mix, and air movement over the tray.

Timing only — the label is the law

This page tells you when to watch for damping off and when treating is worth considering. It is not a recommendation to apply any particular product. Read and follow the product label before you spray — under federal law the label is the legal instruction, and using a pesticide against it is illegal.

Check the pre-harvest interval. Every product that’s cleared for an edible crop sets a minimum number of days between spraying and picking. Find it on the label before you spray anything you intend to eat.
Check the re-entry interval before you or anyone else works in the treated area again, and use the protective equipment the label names.
Confirm the product is registered for your crop in your state. This page groups many different crops together, and a product legal on one of them is not legal on all of them — state registrations differ too. Your state pesticide agency or local extension office can confirm both.
Rates and mixing instructions come from the label, never from us. We don’t publish them because they differ by product and formulation.