How to Prevent Seedlings from Damping Off?


seedling damping off

No gardener wants to check in on their seedlings only to find them with rotting stems and fallen over dead due to damping off! All of those efforts to get off to a great start are destroyed in a matter of just a few short days! What can be done to prevent this heartbreaking disaster? Never fear! There are some proven methods to prevent damping off from happening!

  • Soak pots and trays in a 10% bleach solution for 30 minutes to sterilize them.
  • Use pots with proper drainage holes.
  • Warm soil to 70-75˚F or 21-24˚C
  • Use clean, warm (68–77˚F) or (20-25˚C) water to hydrate seeds and seedlings.
  • Fill trays with fresh potting soil. Don’t reuse old soil and never use garden soil.
  • Sow seeds thinly to prevent overcrowding which leads to humid conditions.
  • Use a potting mix that drains well.
  • Avoid over-watering. Keep the soil moist but not sodden with water.
  • Sterilize all tools that you will use in seedling planting and maintenance.
  • When not in use, store plant containers, and tools in a clean environment.
  • It would be best if you kept hoses and water heads up off of the floor.
  • When sowing indoors, make use of a small fan for proper air circulation.
  • Consider a systemic, broad-spectrum fungicide as a soil additive or soil drench.
  • When direct sowing, check your seed packet for optimal soil temperatures

By using these methods above, you can prevent seedlings from damping off! Let’s see why they are important and how to incorporate them into your gardening practices effectively!

When life hands you dirt plant seeds.

Matshona Dhliwayo

How To Identify Damping Off

Many telltale signs can help gardeners identify the symptoms of damping off. Visual inspection of the seedlings reveals most of the signs readily.

  • Failure of seedlings to germinate.
  • Young seedlings appear mushy with mottled coloring.
  • The stems are thin and fibrous.
  • Stems discolor from the base of the root and rise until the plant dies.
  • The root system is lacking, and those that do form rot from within
  • High humidity causes white fluffy mold, which is caused by Rhizoctonia spp. and Fusarium spp. fungus
  • Seedlings fall over, unable to support themselves
  • Stems thin out at the base preventing the uptake of nutrients
  • The soil remains wet at all times
  • white mold grows on the soil surface as plant rots.

Why Are My Seedlings Damping Off?

Damping-off is caused by cold, wet, and humid conditions usually found in late winter and early spring. These conditions are ideal for multiple bacterias to form. The most common are Pythium and Rhizoctonia Solani. It affects young seedlings and can wipe out entire seed trays.

When temperatures have not climbed enough during the spring, gardeners are trying to get an early start is the perfect time for damping off to occur.

It is important to ensure you do everything you can to provide optimum conditions when growing at this stage to avoid these bacterias’ formation. Some of those ideas are below.

rotting off seedlings

What Can I Do To Prevent Damping Off?

Damping-off can be prevented from ever becoming an issue. As gardeners, we can take action to ensure that we never waste our time and lose our precious seedlings as they emerge. We can follow some of the tips below to avoid damping off altogether.

  1. Cleanliness is key. Sterilize all containers, pots, and tools with Isopropanol Alcohol
  2. Bottom watering will ensure seedlings are not overwatered and allow the soil surface to dry out.
  3. Increase the draining capacity of the potting soil you use by adding perlite to the mix
  4. Pre-warm potting soil before sowing. Cold, damp conditions help the fungus form.
  5. Never use old potting soil for seedlings. This could be contaminated
  6. Sow or pot on seedlings to allow plenty of room for air circulation and prevent humidity.
  7. Increase the ventilation in the room you are raising the seedlings
  8. Once germinated, remove covers or propagator lids to increase air movement.
  9. If no air movement, add a small fan to blow over the seedlings gently.

Optimal Seed-Sowing Temperatures To Prevent Damping Off?

As we have already discussed above, cold wet, and damp conditions provide the perfect breeding ground for the fungus to form that causes damping off. Sowing seed at the optimal time is the most guaranteed way to ensure you avoid this issue.

At Davis, the University of California produced the chart below after a study they performed regarding the best temperatures when sowing certain vegetables to prevent damping off. As you can see, if we waited until some of these temps, we would never grow anything.

infographic on temps required to germinate seeds

The chart above shows the lowest and highest germination temperature ranges for each vegetable crop.
Note the black dot, which shows the “optimal germination temperatures” of each vegetable. Optimal temperatures are the goal for the soil temperature to help prevent the condition known as damping-off of seedlings.

Can You Prevent Damping Off Organically?

In order to prevent damping off, the fungus spores need to be destroyed. This can be achieved in numerous ways organically. The best are below.

  • Bacillus subtillus (Partner)
  • Streptomyces lydicus (Actinovate)
  • Streptomyces griseoviridis (Mycostop)
  • Trichoderma harzianum (PlantShield, Rootshield)
  • Trichoderma virens (SoilGard). 

Each of the 5 organic treatments above can be used as a drench to destroy the fungus spores that cause damping-off when the drench comes into contact with them. This effectively sterilizes the potting soil.

Remember always to follow the directions when handling and applying any fungicides. More than one application may often be necessary to ensure the successful prevention of damping-off of your seedlings.

Can Copper Drench Applications Help Prevent Damping Off?

Copper drenches, such as C-O-C-S and tribasic copper sulfates, are often listed first because they can be safely and effectively applied to many kinds of vegetables.

Note: These are chemically based and not suitable for organic growers!

How To Mix Copper Drench To Prevent Damping Off?

Mix 1 oz copper dust with 3 gal water. Stir thoroughly. The dust is not soluble in water but is merely suspended in it. Stir hard and frequently while applying. Gently drench the plants and soil where the damping-off is occurring. The suspension may be applied with a cup or with a sprinkling after first removing the spray cap from the spout.

This treatment can be used on cucumbers, melons, beets, spinach, carrots, peppers, lettuce, and tomatoes.

Do not use this treatment on cabbage, cauliflower, broccoli, or kale.

Do not try to stop damping off with acids, compounds containing chlorine, or wood ashes. Chemical treatment with metalaxyl as a seed treatment (Apron) or as a soil treatment (Ridomil 2E) can be used to control Pythium damping-off in the field.

What is the best way to sow seed to prevent damping off?

The video below will give you loads of tips on how to correctly sow seeds and raise seedlings. Following these tips will help you to prevent ever having to worry about damping-off in the first place. Check out that video now!

Sowing Seed For Success

Can I reverse the effects of seedlings Damping Off?

It would be every gardener’s desire to be able to reverse damping off, unfortunately, once damping-off has set in, there really is no way to reverse it.  The complete loss of vegetable and flower seedlings is inevitable.

The reason damping-off cannot be reversed is because of the vulnerability of the tiny seedlings, and the rapid spread of the fungi. Seedlings succumb to damping off quickly.

The best method of controlling damping-off is in the prevention of it, to begin with.  It’s important to try to avoid the problem altogether, and you can prevent it by employing some simple and effective measures that I have spoken about throughout this article

Can I put seedlings that died from damping-off into the compost bin?

You should not place seedlings and soil affected by damping off into your compost bins or piles. The fungi’s potential to contaminate the compost is high, causing it to interfere with any freshly sown seeds and seedlings in your garden beds at a later stage.

Damping-off occurs less often in garden beds because the sun warms the soil, and evaporation releases a lot of the moisture from the beds. It can, however, still occur if the soil is not well-draining or the bed is not well ventilated due to overcrowding of seedlings.

This is critically important to note if copper-based chemical drenches have been used, as they remain suspended in the soil. Copper treatments are not to be used with brassicas. If mixed into the compost, it cannot be contained nor isolated.

The safest practice is to dispose of them is into your municipal trash collection to avoid another recurrence of damping off.

You cannot be too cautious concerning the disposal of seedlings and soil that has been exposed to damping off. It only takes one loss of all your seedlings to be painfully reminded to follow prevention methods strictly!

damping off

Conclusion of Preventing Seedlings from Damping-Off

Keep it sterilized

  • Soak all used pots and trays in a 10% bleach solution for 30 minutes to sterilize them
  • Sterilize all tools that you will use in seedling planting and maintenance.
  • When not in use, store plant containers, and tools in a clean environment.
  • You should keep hoses and water heads up off of the floor.

Keep it draining well

  • To ensure proper drainage of excess water, use pots with proper drainage holes.
  • Warm soil to 70-75°F by using a microwave oven, oven, heating mats under trays

Keep it warm

  • Use clean, warm (68–77 F) water to water seeds and seedlings.
  • When direct sowing outside, check your seed packet for optimal temperatures

Keep it fresh

  • Fill trays with fresh potting soil. Don’t reuse old potting soil or compost or garden soil

Keep it spaced out properly

  • Sow seeds thinly to prevent overcrowding

Keep it protected

  • Organic fungicides, or broad spectrum chemical fungicides can be used as a soil additives or soil drenches

Keep it ventilated

  • When sowing indoors, use a small fan for proper air circulation and humidity control

Employing these straightforward and effective preventative measures will ensure your seedlings’ success and a start to a beautiful and bountiful disease-free garden!

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Tony O'Neill

I am Tony O'Neill, A full-time firefighter, and professional gardener. I have spent most of my life gardening. From the age of 7 until the present day at 46. My goal is to use my love and knowledge of gardening to support you and to simplify the gardening process so you are more productive

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