What is damping off

The zeal of greens and other starts emerging from the soil, crisp and bright is something to look forward to. But sometimes our seedlings, even when imbibed with hope and expectancy, keel over before getting much of a start. If you find your seedlings are either not coming up or falling over and wilting near soil level they are probably suffering from damping-off.

Damping-off is caused by fungi that live in soil and is generally encouraged when seeds are over watered, crowded or seedlings are stressed due to factors such as incorrect light and temperature. Infected seeding containers, poor air circulation, overly rich or unsterile soil can also be factors.

Organic Prevention:

  • Water your seeds when their first planted and then, after that, only enough to keep the soil moist. If the soil dries out it will interrupt the germination process but waterlogged soil will increase the probability of damping-off.
  • Give your seeds room to grow and place them in an area with good air circulation.
  • Follow directions on your seed packet or organic gardening guide as to when to plant, how deep to plant, light requirements and optimal soil temperatures.
  • Plant in clean containers using clean tools and consider using sterile soil or a soilless seed starting mix. Avoid mixes with peat moss, coir is far more sustainable.
  • Try bottom watering your seedling flats or pots by placing them in a shallow bin of water.
  • If you’re still running into trouble you can cover with vermiculite or sand to the specified depth instead of soil.
  • Cinnamon and powdered charcoal act as natural fungicides. Try sprinkling the soil surface with one or both for added protection.
  • Finally, follow the breakfast, lunch then dinner principle when planting and transplanting. Breakfast is for seeds, they don’t require a hearty meal but just enough to get going. (In fact, rich soil can burn seedlings as well as encourage damping off.) This is your seed starting mix, baked soil or soilless mix. Lunch is for transplanted seedlings. They’re ready for more nutrition to get to the next stage of growth which is ultimately harvest ready. Plants generally need an extra boost of nutrition just before harvesting in order for fruits, leafy greens, etc. to pack some punch and be as productive as possible. Add rich compost or other organic fertilizers as needed.

Having worked for years in school gardens where many of these measures are difficult to follow, mainly because of time, I’ve found if you simply don’t overwater your seedlings and grow them in an environment with good ventilation you’re already ahead of the game. But it’s always good to have a quiver of tools on hand, especially when you’re eager to get your garden growing.

Has damping off got you down? Do you weep with sorrow as your little green darlings turn brown? Do their roots sport white webbing like some Halloween decoration someone left outside until Christmas? Alas, I’m pretty familiar with this situation. It mimics my day without coffee: I may start off fine but eventually I shrivel up and collapse.

Perhaps you’ve got a serious case of damping off in your own gardens. Perhaps you’re not even sure what it is. Perhaps you’re suffering from extreme paranoia and just want to avoid the problem altogether. Whatever your status, there are a plethora of ways to prevent the disease from taking over, forcing you to throw your trowel in the trash. Here you will find the information you need to keep your plants on a healthy track.

What is Damping Off?

Damping off disease plaguing a tray of microgreens. Microgreens often suffer from this frustrating disease.source

You’ve started your seeds with lots of tender loving care, watching over them like a hawk over the highway looking for road dinner. You do your happy dance as the seedlings sprout, then wail in agony as they drop faster than they appeared. What happened?

Usually the culprit is a fungal disease that has infected the seeds. They have fun-to-pronounce names like pythium, fusarium, and rhizoctonia. If you want to get really technical, fusarium and rhizoctonia are fungi and pythium are classified as oomycetes. But who’s counting, right?

Sometimes the seeds never sprout, other times they do and quickly turn to mush soon after. It can be exceedingly frustrating to lose an entire flat of seedlings in one go.

Often these fungal spores reside in the soil and can be transferred by contaminated garden tools, blown by the wind, or born by insects. Once there, it doesn’t take a lot to destroy a bed of vulnerable young plants.

Symptoms of Damping Off Disease

Thin and brown stems right where the stem leaves the soil: a surefire sign of damping off disease.source

Seeds that resemble the morning mush you used to eat before school are a sign of contamination, usually resulting in a plant that never makes it past the soil level. Shriveling and darkening are also signs. Leaves can appear waterlogged and mushy. When disease is only present in the roots, plant growth is stunted, leading to wilting and death. Affected stems cause the plant to flop. You may even see a white, cobweb-like substance in stricken areas.

While you’re accounting for your plants’ symptoms, ensure that you don’t have other culprits to blame for these issues, such as beetles and cutworms. The symptoms can look very similar, but the treatment and prevention are vastly different. So keep a watchful eye!

Biology of Damping Off Disease

It’s nearly impossible to avoid contaminated soil. These fungal buggers are everywhere and do very well where they are, thank you very much. The potting soil in combination with shared water makes it easy for them to travel from seed to seed. The warmth of indoor conditions get these party crashers going.

That’s not to say you should curb their fun by planting in cold soil. This would slow the growth of the seedling, allowing much more time for disease to spread and take firm hold. A balance needs to be found with temperature, watering and lighting amounts, and fertilization.

Damping Off Control and Prevention

There is no cure for damping off once it has started choking your plants, nor are there fungicides available for garden warriors to do battle, so it’s all about control. You can prevent damping off by following just a few simple techniques and pieces of advice.

Soil Sterilization

There is some debate on the subject of sterilizing your growing medium. It is an oft recommended technique for preventing fungal spores from ruining your seedlings, such as baking your soil at 140 degrees for 30 minutes. Other schools of thought believe that these methods kill off beneficial microorganisms that would otherwise keep pathogens in check.

Whichever you choose, it is probably best to use new potting soil for your seeds every time, perhaps even consider pasteurized or treated soils. If you are using your own soil from outdoors, that’s when giving it a good roasting might be a good idea.


While you’re figuring out whether to bake your soil or not, make sure you’ve chosen a well-draining type of growing medium.

Tool Sterilization

As your favorite gardening implements can carry those nasty spores right into your new seedling flats, make sure everything you use is clean prior to sowing. This may mean cleaning them yourself or using only new containers for your babies. It’ll never hurt to clean your tools before or after every use, even your hose. Yes, that long, green snake may be dragging the bad guys right where you don’t want them to go, so keep an eye on where it lies.

Sow Smart

When sowing your seeds, keep it light and shallow. Too many seeds cause crowding, making evaporation more difficult. Sowing too deep will drag down the seedlings’ growth speed, giving pathogens more time to strangle their hosts, and reduce air circulation.


For indoor sowing, consider using a heating pad to warm the soil around 70 degrees. For outdoor, check the temperature of the soil prior to planting. Wait until the earth has reached optimal warmth for the plants you choose.


Grow lights are recommended to avert damping off. Sufficient light amounts will help the new plants grow vigorously, building quick resistance to disease. A window will not usually be enough. Shoot for at least 12 hours of light, perhaps as much as 16 hours.


Speaking of warm, consider using clean heated water on your seedlings. Cooler water will slow down the growth process. Try to water from underneath rather than overhead, which makes things soggy and gives pathogens an edge. For outdoor gardens, keep your watering time before noon to allow ample time for evaporation. As you’re probably tired of hearing by now, the damper, cooler temperatures of evening will give the fungal spores an advantage over your darlings.


It may be best to wait until you see a few true leaves on your plants, then use only a quarter of standard strength fertilizer. Most potting brands have their own added anyway, so you may even be able to skip this.


For outdoor gardens, rotate your crops every year so you’re not growing in the same spot over and over.


If you ignored or forgot the earlier suggestion of sowing seeds lightly (I’ve never ignored advice, no matter what anyone else might tell you, ahem), you may discover your sprouting seedlings need thinning in order to keep air circulating and evaporation optimal.

To avoid the frustration of losing plants to damping off, think of these suggestions as coffee for your greenery. Getting them off to a clean, vigorous start will help them fight off whatever might attempt to plague them. Once they are past the vulnerable stage, they will start making their own “coffee” and cheerfully greet you every day rather than collapsing in little heaps.

I think I need to go fire up my coffee pot.

I hope you found this article useful and share it far and wide with your fellow gardeners. If you have any tips or experiences of your own, please offer them up in the comments. Thanks for reading!

The Green Thumbs Behind This Article:
Kevin Espiritu
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How to prevent damping off

When you’ve sown your seeds in spring, it can be very disappointing if they germinate poorly, or fail to thrive.


Seeds and seedlings are prone to a fungal infection called ‘damping off’. The very visible collapse of the seedlings is often accompanied by a mass of tiny fungal threads. The fungi develop from microscopic spores that can be both air and waterborne.

Good hygiene is very important, so be sure to use clean equipment and fresh compost. Damping off is encouraged by damp, overcrowded conditions and poor ventilation, so you need to provide the optimum conditions for your seeds.

Here are six ways to avoid damping off and to keep your seedlings healthy.

Wash all pots and trays

Microscopic fungi can survied on previously used pots and seedtrays. Washing equipment will help to remove the majority of the spores and decrease the risk of infection. Soak your pots and trays overnight in buckets or tub trugs of water containing a solution of horticultural disinfectant to moisten any dried-on compost. Once loosened, it will easily scrub off before your containers are rinsed with clean water. Don’t forget to clean propagator lids, too.

Scrubbing soaked plant pots clean

Use fresh compost

Fungal spores are also able to survive in old compost, so for your best chance of success, use a new bag of good-quality sowing compost.

Adding compost to a large planter

Add perlite to compost

Improve the drainage and aeration of compost at the surface by adding perlite or coarse grit in equal parts by volume. This will reduce moisture and humidity levels, which encourage the germination of fungi spores that swamp seeds and seedlings.

Adding white perlite to compost

Sow in cellular trays

Create individual pockets of compost, using pots or cellular trays, to sow two or three seeds into. This will contain any fungal outbreaks of damping-off disease and help to limit its spread among seedlings, so improving their percentage survival rates.

Sowing seeds into cellular trays

Water from below

Stand sown seedtrays or pots in a bowl or bucket filled with 2.5cm of water. Leave in place for about 10 minutes. This will allow water to soak up from the bottom to moisten the compost, rather than soaking the surface where fungal spores tend to thrive.

Advertisement Placing a planted seed tray into a shallow trug of water

Open propagator vents

Make sure that you ventilate propagators to prevent excess humidity building up, encouraging fungal growth. Open vents during the day and close at night to retain warmth. Use a cloth to wipe out the condensation from the inside of the propagator cover.

Propagators with their vents open

Avoid using rainwater

Don’t use rainwater to water your seedlings – it could contain fungal spores.

  • Use a sterile potting mix, rather than soil from your garden. The funguses and molds that cause damping off can live in the soil and outdoor garden soil can harbor all kinds of fungus spores.
  • Start with clean pots. Even the small amount of soil clinging to plant pots is enough to provide a safe harbor for fungal spores. If reusing pots, sterilize in 1 part bleach to 10 parts water.
  • Plant your seeds at the proper depth so they don’t have to work so hard to germinate. Don’t bury the plant’s crown.
  • Don’t crowd your seedlings. Be sure to leave room between them for air circulation. Fungal diseases and mold favor damp conditions.
  • Water seedlings from the bottom, by placing the container in a tray of water. This keeps the seedling itself dry and less susceptible.
  • Add a thin coating of sand or gravel on top of the potting soil, to keep the surface relatively dry. The soil underneath will remain moist, even if the sand or gravel dries out.
  • Don’t overwater your seedlings or leave them sitting in water. Drain off any excess.
  • If possible, create a breeze by placing a small fan nearby and turning it on periodically each day. This will prevent humidity from settling on your seedlings.
  • Give your seedlings plenty of heat and light, so they germinate and grow quickly. Damping off only affects seedlings. If you can get them past the seedling stage, they’re safe.

Damping-Off of Bedding Plants and Vegetables


Damping-off is a disease of germinating seeds and seedlings caused primarily by fungi. Within days, hundreds or thousands of seedlings can become colonized resulting in plant losses and delayed planting or shipping. Healthy appearing plants selected from flats with damping-off may develop root rot or stem canker several weeks later. With some damping-off fungi, foliar blight may also occur. Pythium, Phytophthora, Rhizoctonia and Alternaria are fungi that commonly cause damping-off. There are many other species of fungi that occasionally cause this disease.


Fungi may attack germinating seeds or young seedlings. If poor plant emergence occurs, inspect the soil. If the seed has not germinated it may have been subjected to unfavorable environmental conditions or it may be old. If germination has occurred and the hypocotyl (emerging shoot) is water-soaked in appearance or visibly decayed, fungi are the most likely cause.

Seedlings often develop a darkened or shriveled “wire stem” appearance at the base of the stem. The top of the plant may appear healthy when it falls over but quickly wilts and dies. The roots may or may not be decayed. When seeds are germinated in flats or beds, the disease often occurs in a roughly circular pattern. This is because of the tendency of fungi to grow radially from the point of origin. If there is a lot of fungal contamination, a circular pattern will not be apparent. In plug trays, spread occurs by splashing irrigation water resulting in a more random distribution of disease. The plug cells inhibit the radial growth pattern seen in flats of soil.

Unfavorable environmental conditions and cultural practices can result in seedling death that resembles damping-off. Hot water from sun-baked pipes and hoses, over-fertilization, low temperatures, drought, heat stress and chemical injury can all kill seedlings. However, in most of these cases initial symptoms occur on the foliage or upper part of the seedlings. When the seedlings collapse, the stem at the soil line is usually firm and healthy and the root system is unaffected. An exception to this would be over-fertilization which usually causes roots to appear desiccated and shriveled.

Sources of fungi

Some fungi such as Alternaria are typically seed-borne rather than soil-borne. Alternaria may cause foliar blights on plants as well. Soil-borne fungi such as Pythium, Phytophthora, Rhizoctonia and Sclerotinia may be present in untreated or improperly treated field soil. While not impossible, it is unlikely that soil-less media are contaminated when purchased. However, these fungi can easily be transferred to the growth medium by soiled tools, hands, or hoses and splashing water from infested soil.


Prevention is most important. Avoid contamination of the growing medium and purchase quality seed. Use a soil-less medium. Keep flats off of dirt floors. Hang up the hose ends. When disease occurs, have the cause determined. Drench the medium with a broad-spectrum fungicide or a mixture of fungicides.

When damping-off occurs in a flat, discard the entire flat. Healthy appearing plants may carry contaminated soil and may develop root rot or blight at a later date.

The fungicides listed below are registered for Damping-off and/or Root Rot of Bedding Plants and Vegetables

Fungicides for Pythium and Phytophthora

Common name Trade name Rate *Crops


Aliette® WDG

0.4 to 0.8 lb/100 gal; 2 pts/sq ft.

Drench; however, foliar applications of 2.5-5 lb/100 gal will control root rot of some plants.



Truban® WP and EC, Terrazole 35WP and Terrazole L

See labels

Rates vary depending on the formulation. Irrigate immediately with additional water equal to at least half the volume of the fungicidal drench.



Subdue Maxx, Mefenoxam 2AQ

See labels

Rates vary depending on the plant. Subdue has broad crop clearance for ornamentals.




3.2-6.4 oz per 50-100 gal.

Apply when plant roots are well established on a 10-14 day interval. Use enough solution to wet root zone. Avoid irrigation for several hours before application.




1.0 to 4.0 fl oz/100 gal

Must be tank mixed with another labeled fungicide with a different mode of action.



1.5 to 3.0 fl oz/100 gal

Apply as a dench or to soil surface. Do no make more than two applications per crop cycle.

Potassium salts of phosphorous acid


6.25-12.75 fl oz/100 gal

Apply 25 gallons to 100 sq ft. Follow application with irrigation. Repeat as required. Limit to one application per month.


thiophanate methyl plus etridiazole

Banrot® 8G

See label

Irrigate immediately with additional water equal to at least half the volume of the fungicidal drench. Also controls Rhizoctonia, Fusarium, Thielaviopsis and Cylindrocladium .


fludioxonil plus mefenoxam


1.5 fl oz/100 gal

Applictions to Impatiens, New Guinea Impatiens, Geraniums, Pothos or Easter lily may cause chlorosis or stunting.




2-3 fl oz/100 gal; see label for details.

Drench at 3 to 6 week intervals. May be tank mixed with thiophanate methyl for control of Rhizoctonia.


Streptomyces griseovirdis


Suppression of Pythium that can cause seed, root and stem rot. Contains a beneficial bacterium. Repeat applications may be needed. Use as soil spray or drench. Acts as a preventative. Will not cure diseased plants.

Vegetable Plants,

Trichoderma virens


Contains a beneficial fungus. Acts as a preventative. Will not cure diseased plants. Do not use other soil fungicides with SoilGard at time of incorporation.

Vegetable Plants,

Trichoderma harzianum


Contains a beneficial fungus. Avoid applications of fungicides a least one week before or after application. Acts as a preventative. Will not cure diseased plants.

Vegetable Plants,

Hydrogen dioxide

Oxidate, ZeroTol

Contact, oxidizing sanitizer.

Vegetable Plants,

Fungicides for Rhizoctonia

Common name Trade name Rate *Crops

thiophanate methyl

Cleary’s 3336
Fungo Flo
AllBan Flo

See labels

See label for seedlings and transplants. Cleary’s has broad crop clearance for ornamentals. Use experimentally for plants not on the label. Rates vary depending on the formulation.



26 GT
Chipco 26 GT
Iprodione Pro

See labels

See label for rates. Active primarily against Rhizoctonia . Apply 1 to 2 pints of solution per sq. ft. and repeat at 14 day intervals. Do not use as a drench on impatiens.


iprodione plus thiophanate-methyl

13.5 fl oz/100 gal.

Do not apply as a drench to Impatiens or Pothos.



Terraclor® 75WP or 400F

4-8 oz/100 gal.

See labels for rates. Broad crop clearance for ornamentals. Active primarily against Rhizoctonia and Sclerotinia .

Vegetable Plants

thiophanate methyl plus chlorothalonil

Spectro 90 WDG

1.0 to 2.0 lb/100gal

See labels for specific instructions.


thiophanate methyl plus etridiazole

Banrot® 40WP

see above

see above

see above



1 to 2 oz packets/100 gal.

For Rhizoctonia , apply sufficient water to wet the top half of the growing medium. For other pathogens, completely drench the growing medium. Medallion can be mixed with Subdue for broad spectrum control.



Terraguard 50W

4-8 oz/100 gal; 4 fl oz/6 inch pot.

For best results do not irrigate with additional water until 24 hr after application. Apply at 3-4 week intervals as needed. Do not use on impatiens plugs. On impatiens transplants, do not exceed 2 oz/100 gal.




0.2-0.9 oz per 100 gal. 1-2 pt per sq ft at 7-28 day interval.

Do not make more than two sequential applications of Heritage. Do not rotate with Compass. Use caution applying to small bedding plants as phytotoxicity can occur.




0.5 to 1 oz per 100 gal. Drench to wet upper ½ of growing medium.

Active against Rhizoctonia, Cylindrocladium, and Phytophthora parasitica. Do not make than two sequential applications. Do not rotate with Heritage. Do not apply to vegetable transplants.




3 to 6 one oz packets/100 gal.

See label for volume of drench.


pyraclostrobin plus boscalid


8.0 to 12.0 oz/100 gal

Use caution when applying to Impatiens and petunia when flowering.


Streptomyces griseovirdis


Suppression of Rhizoctonia that can cause seed, root and stem rot. Contains a beneficial bacterium. Repeat applications may be needed. Use as soil spray or drench. Acts as a preventative. Will not cure diseased plants.

Vegetable Plants,

Trichoderma virens


Contains a beneficial fungus. Acts as a preventative. Will not cure diseased plants. Do not use other soil fungicides with SoilGard at time of incorporation.

Vegetable Plants,

Trichoderma harzianum


Contains a beneficial fungus. Avoid applications of fungicides a least one week before or after application. Acts as a preventative. Will not cure diseased plants.

Vegetable Plants,

Hydrogen dioxide

Oxidate, ZeroTol

Contact, oxidizing sanitizer.

Vegetable Plants,

*Crops: Crops registered for use.

See labels for rates and a complete explanation of precautions and restrictions.

Note: More than half of Pythium isolates cultured from greenhouse grown plants have been found to be resistant to Subdue Maxx. Do not use the same fungicide repeatedly, and rotate outside of a fungicide group.

Tables revised 12/2013 by M. Bess Dicklow, UMass Extension Plant Diagnostic Lab

Links to Further Resources on the Web

  • Photos, University of Massachusetts and University of Connecticut Photo Library
  • New England Greenhouse Floriculture Guide (Insects, Diseases, Weeds and Growth Regulators)

We have been vegetable gardening for a few years now and there is one issue that has come up on occasion when starting our seeds inside – it is called “damping off.” This is basically mold or fungus that develops in the soil or at the base of your seedlings. You do want to get rid of this as it can cause disease and damage to your seeds, plants and crops.

It is usually caused from overwatering and/or too much humidity. When we plant our seedlings, we mist to water with a spray bottle and cover with plastic wrap. Once they have sprouted, we then water with a little bit of water and keep uncovered. If you overwater, you can use a fan to help dry out the excess water.

If damping off does occur, here’s some natural ways to take care of it! Do this at the first signs of damping off or mold!

  • Start with clean or new seed starting pots. If you are reusing any pots, be sure to wash in hot soapy water rinsed well to kill and get rid of old bacteria from previous plantings.
  • If damping off occurs, try one or more of these methods to “nip it in the bud!” (Pun intended!)
    • In a 32 oz spray bottle, mix 1 TBSP (or 1/2 ounce) of 3% hydrogen peroxide with water. Mist your seedlings with this mixture to cure damping off.
    • In a 32 oz spray bottle, mix 2-4 TBSPs of strong brewed chamomile tea and mist seedlings to cure damping off.
    • Sprinkle your seedlings with ground cinnamon.
    • Spring your seedlings with ground activated charcoal.

Any of these methods to help prevent and cure the damping off. The best one we have found has been cinnamon – it is also the easiest as you can pull it out of your spice cabinet and sprinkle it on! You may need to repeat any of the above until the problem is resolved!

How have you cured damping off on your seedlings?

See more Gardening Tips

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In my opinion, there is no greater satisfaction than planting your own seeds and watching them grow into little baby seedlings.

More than just being a magical process to watch, it can also mean you get to play around with interesting varieties you might not find in your local garden center, and learn about your plants much more intimately than you would otherwise.

But then! Tragedy strikes and your seedlings come down with a serious case of “damping off.” But what is damping off, you might ask?

Well, this guide will explain everything you need to know about this disease and how to prevent it from affecting your seedlings.

“Damping off” is a soil-borne fungal disease that affects seedlings, causing the rotting of stem and root tissues at and below the soil surface of the young plants.

The term is quite a general one, encompassing several disease-causing culprits, the most common of which are well-known fungal foes such as Rhizoctonia spp., Fusarium spp. and the water mold Pythium spp.

This disease affects a wide variety of vegetables and flowers. Infected plants usually germinate successfully and come up fine, but start to show signs that all is not well a few days down the line.

Young leaves, roots, and stems of newly emerged seedlings are all highly susceptible to infection.

This disease causes such major issues in the root system of the plant that seedlings infected by damping off rarely survive to produce a vigorous plant. Even worse, it is usually a large section, or an entire tray of seedlings that is killed.

In short, this fungal infection can really decimate your seedlings, and proper care needs to be taken to prevent a tragedy from occurring.

The good news is that, although mature plants can still be affected by these pathogens, from the moment your plants have mature leaves and a well-developed root system, they are much more resistant the fungus or mold that causes damping off.

There is therefore a critical period of growth between planting and maturity when special care needs to be taken to protect sensitive seedlings.

How to Identify Damping Off

The most common way damping off will present itself is when your plant stalks become water-soaked, thin and mushy, and fall over at the base and die.

The seedlings, especially the cotyledons (the first leaves produced) may have a kind of gray-brown color, and young leaves will wilt and turn from green-gray to brown.

It is also common to see a fluffy white cobweb growth on infected plants.

When you pull your plants up, you can also see signs of the disease on their root systems. Roots on infected plants are either absent, stunted, or have grayish-brown sunken spots.

Prevention and Protection Measures

I’ll give you the bad news first:

Once your plants catch a case of damping off, they’re done for. There is nothing we can do to cure this disease once it’s taken hold, and even if there was, the tiny seedlings die so quickly that there would be very little time to help even if you could.

The good news is that, as damaging as it is, there are a few practical, actionable steps you can take to see off damping off before it becomes established.

There are two P’s that you should keep in mind when it comes to damping off – prevention and protection.

Prevention Tips

Preventative tips include:

1. Use a sterile potting mix, rather than soil from your garden.

The fungi that cause this disease live in the soil, so preventing soil contact with your vulnerable seedlings is the first good place to start.

If this really isn’t possible for you, or if you plan to reuse soil mix, then you can also sterilize your soil.

You can do this by baking it in the sun. But in my experience, I’ve found that it’s quicker and easier either to use either your oven or your microwave. Personally, I prefer doing it in the microwave, as heating in the oven can generate a funky smell.

Just put your soil mix in a suitable container, cover it loosely, and heat on high for 8-10 minutes. It will get hotter than you might think, so be aware of this when you’re handling your soil mix afterwards.

Heating up your soil in this way helps to kill any fungal foes lurking within.

2. Use clean pots.

Fungal spores are tiny and can reside in even the smallest amount of soil residue left in pots. It’s best to sterilize your pots before using them, using a mixture of one part bleach to 10 parts water.

3. Help your seeds as much as you can.

Anything you can do to minimize your plants’ struggle helps to maximize their strength.

This includes planting them at the right depth, so they don’t have to work so hard to germinate, getting your soil substrate mix right, and choosing a sunny, warm spot for them to thrive in.

4. Don’t overcrowd your seedlings.

This isn’t because your seedlings don’t like company, but because ensuring room for good air circulation is key to preventing fungal disease from gaining a foothold.

Going one step further, this could even include using a fan to help circulate air around your baby plants.

5. Water from the bottom up.

Watering from the bottom up means that the seeding itself stays dry, and is therefore more protected.

You could also add some surface sand or gravel around your seedlings to help keep them high and dry.

Continuing with the irrigation theme, it’s also important not to over-water plant starts.

6. Remove any suspect plants immediately.

I’m the first to become emotionally attached to my baby plants, and I am absolutely loathe to kill any of them. But it’s better to be ruthless here.

The moment you suspect one plant might be showing signs of damping off, it’s best to get him out of there to stop him from infecting his neighbors. Better safe than sorry!

Protection Tips

In my experience, conventional fungicides aren’t really worth trying. But I have had luck with a few of these homemade protective concoctions.

To be clear, they are only useful to protect against – not to cure – this disease. But they can give you that little edge that might make all the difference.

  • A strong brew of chamomile or cinnamon tea isn’t just a nice nightcap for us. You can also use it to water and/or mist your seedlings.
  • Mix in a splash of hydrogen peroxide per quart of water and mist seedlings with it.
  • Apply a light dusting of cinnamon to the soil surface. I’ve found this to be especially effective!
  • Applications of compost tea may also help, as it is full of beneficial bacteria and fungi that out-compete many bad pathogens.

Remember Your P’s!

And here I don’t mean please! Protection and prevention are the name of the game in beating damping off. By following all the tips above, you stand a fair chance of avoiding and even overcoming this disease.

Have you had any experience with damping off? Or have any extra tips to add? Let me know in the comments section below!

If you loved this article, be sure to check out these as well:

  • Integrated Pest Management : What It Is and How to Use It
  • The Benefits of Using Soil Inoculants and Microbes in the Garden
  • How to Start Worm Farming: Adventures in Composting and Vermiculture


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About Natasha Foote

With a passion for soil health and growing trees, Natasha Foote is a biologist who was hit with a serious case of green fingers, and decided to swap sterile laboratories for getting her hands dirty in the soil. Formerly a farmer and researcher working with the agroforestry project Mazi Farm in Greece, when she wasn’t working on the farm, she was busy studying soil biology under the microscope. Now, you can find her in the south of France where, in between enjoying all the fresh peaches, plums, apricots, and cherries that the area has to offer, she’s working on various agricultural projects whilst writing about all things green.

What Is Damping Off?

Damping off is a term commonly used for indicating the sudden death of seedlings, often caused by soil-borne fungus stimulated to grow by nutrients from a germinating seed. On rare occasions, however, the sudden death of seedlings may be caused by other factors. Damping off can be alarming to a gardener trying to grow seeds and can leave them asking, “What is damping off?” and “What does damping off look like?” Learning how to prevent the conditions of damping off will help keep your seedling happy and healthy.

Damping off occurs in many types of soil and in various climates. The amount of damage to seedlings depends on the particular fungus, soil moisture and temperature. Typically, germinating seeds are killed by the damping-off fungus prior to emerging from the ground, and older, more established plants are seldom affected. However, portions of the roots and stems can still be attacked, resulting in poor growth and reduced yields.

What Does Damping Off Look Like?

So what does damping off look like? This often depends on the particular fungus. Generally, infected seeds become soft or mushy, turning brown to black in color. Seeds that have already germinated develop brown water-soaked spots.

Seeds may be infected as soon as moisture penetrates the seed coat or later as growth begins. The otherwise healthy looking seedling will discolor or wilt suddenly, or simply collapse and die.

Other signs of damping off include stunting, low vigor, or wilting. Foliage of plants may yellow and fall prematurely. The roots of a diseased plant will appear brown or black with evidence of water soaking.

Conditions of Damping Off

Unfortunately, the conditions required for seed germination also create favorable environments for the growth of fungus, as both seeds and roots must be kept moist and warm. The conditions of damping off vary depending on the fungus.

Normally, however, cool, wet soils favor development of the disease. For instance, the fungal disease Pythium root rot occurs with cooler temperatures in poorly drained soils. The lower portion of the stem may become slimy and black. Rhizoctonia root rot occurs with moderate moisture levels in warm to hot temperatures. Infected plants often have sunken lesions on the stem at or below the soil line.

Fungicide to Prevent Damping Off

Various practices may be helpful in reducing the amount of damping off infection. It may help to water less often or apply fungicide to prevent damping off. Fungicides may be applied as a soil drench after planting, incorporated into the soil as a dust before planting, or sprayed in mist form on all seedlings. Once transplanted, only those seedlings known to be especially sensitive to damping off need be misted with fungicide daily until the first or second seed leaves have emerged.

Another option may include seed treatment. Damping off can be reduced by planting fungicide-treated seed directly into the garden. Other preventative measures include using well-drained soil and avoiding overcrowding of plants. Also, clean out all pots thoroughly before reuse and discard contaminated soil.

Now that you know the answers to what is damping off and what does damping off look like, you can successfully keep it from happening to your seedlings. With a little TLC seed treatment, damping off will be a thing of the past.

Damping Off

One of the most depressing of problems for the gardener is when seedlings collapse and die just after they’ve come through.

Dr. Dorothy Derbyshire explains what exactly damping off is and how to prevent it. At the beginning of a new season, most gardeners feel a sense of expectancy.

From coloured photographs in catalogues and on seed packets they think immediately of wonderful displays of bedding plants or of tomatoes ripened on the plant and used for a salad.

However, a lot can happen between seed sowing and the final crop especially in the early stages. Seedling death, poor development or uneven growth caused by damping-off diseases are particular problems.

As more F1 hybrid seed varieties, which are more expensive than open pollinated seed become available it really is important to give the seedlings the best possible conditions for growth. Seedling collapse, or damping-off is a wide-spread problem for gardeners and commercial growers.

As seeds germinate they may be attacked or the seedlings may be infected in the post emergence stage. An affected seed tray would have a bare area of compost, probably near one end, surrounded by seedlings growing poorly. Some seedlings might have collapsed at the base with a water-soaked appearance.

After pricking off, seedlings may develop brown root tips, have a weak root system, or collapse at the stem base and fall over. This is commonly seen when tomatoes are pricked off, and the seed leaves turn a very dark green.

Causes of damping off

Damping-off diseases are caused by fungi. These microscopic organisms form colourless threads in soil, compost, or plant structures. The ones attacking seedlings are species of Pythium and Phytophthora, belonging to a group called the water moulds. This name highlights the conditions which favour the spread of these fungi. They flourish in wet compost and need water to spread from plant to plant.

In addition to the colourless threads, these fungi develop microscopic, circular or pear-shaped bodies containing minute motile spores. If a Phytophthora colony is examined under high magnification in water, it is possible to see the self-propelled spores bursting out of the pear-shaped container and swimming through the liquid by lashing two fine threads.

When the water is cold they move slowly and take a long time to come to rest, whereas at 68F (20C) the spores swim quickly but soon stop. If they rest on a root or stem surface a minute thread emerges and penetrates the plant cells. These fungi grow inside the plant and disrupt the normal cell processes.

Mycologists consider them to be a relatively primitive type of fungus because the spores are motile and require water for dispersal. Other fungi such as powdery mildews or rusts do not have this requirement.

There is another common soil-borne fungus which attacks seedlings, leading to collapse. This is called Rhizoctonia. Infected plants tend to develop a dry, reddish-brown stem rot called wire-stem, or the seedling roots may be affected. Seedlings in patches are unthrifty or pale coloured and die slowly. When conditions are moist it may even be possible to see the dark coloured fungus threads with a lens, on the plant or the compost. If a badly infected seedling is pulled up an excessive amount of soil may hang from the shriveled root indicating the weft of fungus growth on the root. Rhizoctonia does not develop spore-containing bodies like the water moulds, but spreads entirely by the threads which grow through the compost. All members of the brassica family seem particularly susceptible to infection.

Susceptible plants:

  • Pythium and Phytophthora
  • Antirrhinum
  • Celery
  • China aster
  • Cineraria
  • Cucumber
  • Lobelia
  • Marigold
  • Nemesia
  • Rhizoctonia
  • Aubrieta
  • Brassicas
  • Salvia
  • Stock
  • Wallflower

Preventing attack

Although some plants are especially prone to damage, it is best to take sensible precautions against these diseases whatever seed you plan to sow as any plant can suffer.

Before you can plan to control any plant disease, it is important to know where the fungus comes from and how it is spread. Some diseases only survive on living plants, while others can be carried inside the seed. In the case of the damping off diseases they are soil-borne but can survive in plant or soil debris. The water moulds spread most in wet compost, while Rhizoctonia is active in drier conditions.

The most fundamental principle in preventing these diseases is hygiene. The containers, such as pots and seed trays, the greenhouse and all tools must be cleaned and free of soil or plant debris. Soak the containers in hot water and scrub them thoroughly with a bristle brush to dislodge small particles of soil or debris. You may choose to use a proprietary disinfectant – if you do, make sure you ventilate the containers before use to release any remaining fumes. If you plan to stand trays on the soil floor of the greenhouse cover the soil with polythene or raise the trays up from the surface so that they don’t touch the soil. You may have the advantage of a heated propagator which is excellent for germination, but watch that you put the trays afterwards on clean benching and don’t expose the seedlings to a sudden change in temperature or low night temperatures.

Watering and seed compost

Besides contaminated containers the water moulds can survive in stored water. You might think that it is good to use rain water collected from your greenhouse roof and stored in a butt or tank. Certainly it is said that slightly warmed water, at the temperature of the greenhouse is best for plants. But an uncovered tank in a greenhouse soon collects plant debris, dust, and algae and spells trouble in propagation. Always use fresh mains water for moistening compost and watering seedlings. You can draw off the tap water into a can, and leave the water to warm up before use the same day.

On the seed packet there will probably be instructions on how deep to sow the seed, and the temperature for optimum germination. What the packet may not mention is the compost to use and how to manage it.

Do NOT use garden soil. would generally recommend a proprietary compost formulated for seed sowing. These composts give the seedlings the best start in life, if they are prepared correctly.

By chance, the compost may be just moist enough, as you turn it out of the bag. But it may not; and to test it, take a handful of the compost and squeeze it, open your hand and let it fall on the bench. If the compost does not bind and just hold together it is too dry. If moisture oozes between your fingers it is far too wet. To moisten the compost turn out sufficient compost onto the bench for your immediate need. Make a flat layer, and gently sprinkle water on the compost surface. Then turn and mix the compost with your hands. Do the hand test again, and continue until the compost just holds together, but drops apart as it falls on the bench. Once the compost feels right sowing can proceed. It is quite wrong to sow seeds in dry compost and then give a heavy watering. This is the way to get damping-off.

Don’t use too large a container because large volumes of compost warm up slowly. When you have sown the seed as directed on the packet, only moisten the compost surface if a fine seed is involved. Cover the tray and put it at the appropriate temperature. Once the seed is surrounded by moistened soil it will germinate.

In some circumstances people use such places as the airing cupboard to germinate seeds that need high temperatures. But, alas, they may forget them and when the seeds are brought out the hapless seedlings are etiolated and unfit for the normal environment. Young plants which are grown at the appropriate temperature in light are more resistant to disease, because they are sturdy, well balanced plants. Those taken out of the airing cupboard would be much less likely to be resistant. Aim for strong, sturdy growth at moderate temperatures.


Commercial growers have certain fungicides which are either mixed into the compost or applied as a drench treatment before or after sowing. As yet these are not available to the amateur gardener. There are two types of treatment you can use; one is to buy a proprietary, powdered seed treatment which contains a fungicide which will reduce the possibility of infection. Shake some dust with the seed as directed and sow normally. It pays to test small batches of seed first as the dressing can harm some varieties. A liquid copper formulation or Cheshunt Compound, also with a copper base, can be used on seedlings but they can slow down the growth of very .delicate plants. If there is one type of seed which you have trouble with regularly, it could be worth finding out if young seedlings are sold ready germinated. A limited range of young plants are becoming available now from seed suppliers.

Rescuing infected plants

Finally, what happens if, despite your care, seedlings do collapse in part of a seed tray? I would not recommend salvaging the remaining seedlings which appear to look normal. They may seem unaffected, but as these diseases are soil-borne, they may not be healthy. If you transplant these seedlings some roots or rootlets must get broken, and if the fungus threads are there in the compost, then the fungus will attack the plant. If you over-water it to ”settle the plant in’ then the water moulds will become active, or if you keep the compost on the dry side Rhizoctonia could infect, according to the plant you are growing.

You may have a problem with some very choice or valuable seed. In this case the salvaged seedlings should be kept in the intensive care unit! They should be potted individually into small pots of moistened compost and segregated from other plants. They should be kept warm and sprayed over with a mister regularly to keep the leaves turgid. Drench the compost of a few with copper fungicide and leave the rest alone. This treatment combined with a good growing environment should allow the roots to start growing rapidly, and you may, by this means, be able to salvage a proportion of the plants.

Dr. Dorothy Derbyshire is an expert in plant diseases with the Ministry of Agriculture.

Source of article
Growing From Seed – Spring 1987 Vol. 1 Number 2
The Seed Raising Journal from Thompson & Morgan

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