Preventing Damping Off

Have you ever sown seeds indoors and no seedlings appeared, or seedlings appeared only to suddenly collapse and die? The culprit may have been damping-off. Damping-off is a term that describes the death of seedlings due to rot. There are several species of fungi that may attack seedlings and lead to damping off. Rot can occur soon after germination—so soon that the roots are killed and no stem appears. Damping-off may also occur just after the stem appears, or after seedlings have put on some healthy-looking growth. The seedling may suddenly wilt, or it may keel over from its base.

The best protection against damping-off is an ounce of prevention. Here are some easy-to-follow measures:

Ensure good drainage in seedlings’ pots and trays.

Ensure good air circulation where the seedlings are growing. Set up a small fan to keep the air moving.

Ensure good light to promote strong growth, whether seedlings are in a window or on a light stand.

Use clean seed-starting equipment, including containers and sterile seed-starting mix.

Water from below by placing the pots or trays in a container of water or on a capillary mat. The water will soak up through the drainage holes. Once the top of the soil looks moist, remove the pots or trays from the water.

When sowing seeds, cover them only to the depth recommended on the packet, and no deeper. Instead of covering them with your seed-starting mix, cover them instead with sphagnum moss, coarse sand or chicken grit. These materials are less likely to host fungi.

Once seedlings appear, mist them daily with weak chamomile or clove tea, and/or dust the soil surface (one time only) with ground cinnamon or powdered charcoal.

One more tip for healthier, stronger seedlings.

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Learn more about seed starting with the Brooklyn Botanic Garden Guide to Starting From Seed or Success With Seeds.

Check out Clarington Forge’s planting dibber, a great tool for planting seeds or transplanting seedlings.

Learn the ins and outs of all propagation techniques with The Plant Propagator’s Bible.

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5 thoughts on “Preventing Damping Off

  1. Pingback: Suburban Hobby Farmer The Best Gardening Blog Posts This Week

  2. Inoculating the soil medium/seeds with beneficial bacteria either by means of the use of compost tea or commercially available products is also a good way to start off seed flats (somewhat like eating yogurt strengthens one’s immune system). These beneficial organisms colonize roots and soil to keep the marauders down while improving the uptake of nutrients by the seedlings.

  3. I typically use a plastic dome to cover my seeds while they’re germinating and until they’re a few inches tall. After reading this article, however, I’m thinking I should probably remove the cover as soon as they poke out of the soil. Or is it OK to keep it on for a couple weeks? Would that encourage damping-off?

    • I use a plastic covering just until the seeds have germinated; then I remove it to encourage air circulation. When I’ve left it on longer, I’ve had more damping off and also leggier seedlings. I hope that helps.

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