How to Prevent Seedlings from Damping Off?

Any gardener may feel distressed when they examine their seedlings only to find them with rotten stems, collapsed, and died due to damping off. Their strenuous efforts to secure a healthy start can be destructed within days. How can one avoid this stirring disaster? Fear not, there are some proven methods that can be used to prevent damping off!

  • 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 saturated with water.
  • Sterilize all tools that you will use in seedling planting and maintenance.
  • Store plant containers and tools in a clean environment when not in use.
  • Keeping hoses and water heads up off the floor would be best.
  • When sowing indoors, use 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 essential and how to incorporate them effectively into your gardening practices!

When life hands you dirt plant seeds.

Matshona Dhliwayo
seedling damping off

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 characters 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 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 the 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 bacteria 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 trying to get an early start is the perfect time for damping off.

You must do everything possible 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 potting soil’s draining capacity 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 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 there is no air movement, add a small fan to blow over the seedlings gently.

Optimal Seed-Sowing Temperatures To Prevent Damping Off?

As 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 avoid this issue.

At Davis, the University of California produced the chart below after a study 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 each vegetable crop’s lowest and highest germination temperature ranges.
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?

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

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

Each of the five 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, and 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 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 three 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. After removing the spray cap from the spout, the suspension may be used with a cup or sprinkling.

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 a soil treatment (Ridomil 2E) can 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 many tips on correctly sowing seeds and raising 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?

Every gardener would desire to reverse damping-off; unfortunately, once damping-off has set in, there is no way to change it. The complete loss of vegetable and flower seedlings is inevitable.

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

To begin with, the best method of controlling damping-off is to prevent it. It’s essential 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 much moisture from the beds. It can, however, still happen if the soil is not well-draining or the bed is not well-ventilated due to overcrowding of seedlings.

It is 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, they cannot be contained or isolated.

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

You cannot be too cautious concerning the disposal of seedlings and soil 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.
  • Store plant containers and tools in a clean environment when not in use.
  • You should keep hoses, and water heads up off of the floor.

Keep it draining well.

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

Keep it warm

  • Use clean, warm (68–77 F) 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 soil additives or drenches.

Keep it ventilated

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

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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