why are my indoor seedlings dying

Seedlings Suddenly Wither Away? How to Avoid Damping Off

You’ve planted your seeds in their containers.

You’ve watered them carefully and kept them warm.

You’ve watched as they germinate and start to grow.

And then, all of a sudden, one by one they just lean over and die.

Most gardeners have been there at one time or another. And most gardeners will have plenty of advice on how to stop it from happening again. There is, however, a growing school of thought that is breaking from conventional wisdom on at least one important aspect of how to prevent what’s known among gardeners as damping off.

What Is Damping Off?

Damping off — a horticultural disease caused by numerous fungi and other pathogens — can move through an entire tray of seedlings in a matter of days. It is probably the single biggest problem for gardeners who start their seedlings indoors.

If you’re not sure what to look for, here’s how the Texas Plant Disease Diagnostic Lab at Texas A&M; describes the phenomenon:

Typical symptoms occur soon after plant germinates. This can occur very quickly and appear to start at the base of the seedling. It may begin with a water-soaked appearance before progressing to becoming a constricted darken region. While seedling tops may still be green, they tend to flop over due to the loss of structural integrity. . Sometimes these fungi can attack the germinating seedling before they emerge resulting in a what appear to be poor germination rate. But upon closer inspection, you might find rotten tiny seedling on the surface of the soil.

The Basics of Preventing Damping Off

Once started, damping off can be very hard to treat. That’s why most gardening websites and articles focus on prevention, rather than cure. Here are some of the measures that are recommended by almost everyone to keep damping off from infecting your seedlings:

  • Ensure adequate air circulation: According to John Fendley (aka Farmer John), founder of the Sustainable Seed Co., providing adequate air circulation is the single most important aspect of raising healthy seedlings. Removing or opening up the cover on a cold frame, or opening the vents on your greenhouse, will allow air to circulate and prevent pathogens from building up on seedlings. Adding a fan can also help to improve air circulation — with the added benefit that a light breeze will also cause seedlings to grow stockier, sturdier stems.
  • Don’t water too frequently: Before seeds germinate, the growing medium needs to remain moist. Once seedlings have appeared, however, you should allow them to dry out before watering again. Watering from below can also help prevent plant stems and leaves from getting wet, thus also decreasing the likelihood of fungal or mold infections. In addition to exercising moderation when it comes to watering, Farmer John also cautions growers to ensure that all containers have adequate drainage to allow excess moisture to escape.
  • Maintain correct temperatures: Allowing plants to become either too hot or too cold can increase vulnerability to damping off. Protect seedlings from frost with a cold frame or greenhouse — but be sure to provide ventilation during the day so temperatures don’t get too high. Providing bottom heat to seedlings with a heating mat can speed up germination. However, once plants have germinated, plants like tomatoes should be removed immediately from the heat mat to avoid them becoming leggy. Peppers, on the other hand, are said to benefit from bottom heat for at least two weeks after germination has occurred. Check temperature recommendations for each seed you are starting, and use a soil thermostat to control your heating mat and avoid overheating.

So far, so uncontroversial.

But read most conventional gardening resources and they will tell you that you should also sterilize your seedling soil in order to eliminate any pathogens it might contain. Many gardeners, in fact, will literally bake their soils and seedling mixes in the oven to remove microorganisms and create a supposedly “safe” environment for their soon-to-be-born young plants.

There is, however, a growing school of thought that suggests this might in fact be counterproductive.

Probiotics For Plants

Troy Beuchel, horticultural specialist for Premier Tech Horticulture — makers of Pro-Mix Ultimate Organic Seed Starter Mix explains why his company actually adds fungi and other microorganisms to its seedling mediums, and why they urge gardeners to not sterilize their soils:

“Damping off pathogens are typically not coming from the growing medium. They are a lot like the common cold — they are everywhere in our environment. Sterilizing the growing medium is not good because it kills any natural microorganisms that come from the peat/compost. These natural microorganisms use root exudates as food. Damping off pathogens also use these exudates as a food source. If the natural microorganisms are present, they use up the food coming from the plants roots which slows down the rapid development of plant pathogen populations. If the growing medium is sterilized, the pathogens still enter the growing medium. Since all the natural microorganisms have been killed, there is nothing in the growing medium to keep plant pathogen populations from quickly establishing and overwhelming plants.”

Healthy Soil Means Healthy Plants

This view is backed up by Justin Kirby of Fox Farm Fertilizer, another maker of organic soils and soil amendments which formulates its Light Warrior seedling starter mix using a diverse range of inputs including mycorrhizal fungi, beneficial microbes, humic acid and earthworm castings:

“As with sick people, killing all bacteria both beneficial and detrimental is not always the best approach. A great practice for germination of healthy plants without damping off is to load the soil with beneficial bacteria and fungi like mycorrhizae, and bacillus subtilis. This most closely resembles how things happen in the wild. Without healthy living soil, we can’t truly expect healthy living plants.”

How Live Soils Boost a Seedling’s Immune System

Alison Jack, a researcher at Cornell University, has demonstrated how one particular water mold known as Pythium aphanidermatum, a common culprit in damping off, is inhibited by the presence of microorganisms commonly found in worm compost. Jing Jin of the Cornell Daily Sun explains more:

“The microbes present in compost are the key to suppression. These microbes colonize the seed surface within eight hours of being planted in vermicompost. The microbes chemically modify the seed as it germinates so that signaling between the seed and the motile zoospores of P. aphanidermatum is interrupted, preventing the pathogen from accessing the plant.”

Jack explains in more detail how the disease-suppressing qualities of vermicompost work in the video below:

The Hidden World of Soil

With scientific knowledge increasing about the vast diversity of species under our feet, it’s perhaps no wonder that many gardeners are finding benefits in promoting living soils.

Just as rice farmers have increased yields through nurturing soil biodiversity, so too many growers are now finding that a sensible approach to disease suppression is more about nurturing beneficial microorganisms rather than adopting a kill-everything-that-moves approach of creating lifeless, sterile growing environments. The more we learn about the complex relationships in our soils, the better we’ll be able to fine-tune our strategies for fighting damping-off and other diseases.

Here's how to keep your young plants from succumbing to this common disease.

My seedlings keep dying!!

Gardening Reference » Gardening in 2006

I don’t get it. My seedlings start fine and then die in a couple of weeks. I am mostly trying to start peppers but have a bunch of other stuff too.
I have a cabinet that I made into a seed starting area. I have two cool florescent lights about 3-6 inches above them that are on for about 15 hrs a day. I have a heater in the bottom to bring the soil up to about 80-85 degrees on top and 70-75 on the bottom. I water with rain water and a 10-52-10 mix to help them start and I use Supersoil for soil. I usually wait to water them till the top gets a little hard but is still wet on the bottom. I have them in the seed starter trays so I just add the water to the bottom and it soaks up.

More on the problem. Lets say my tomatoes, they came up and were doing just fine. I then go in one day and one of 4 is limp and starting to fall over. Then a few days later another. then another. The last one is going limp right now. I also had a pepper that I finally got to grow, and it just died. All about 2-3 weeks from popping up. I have some new peppers that I just started and I don’t want it to happen to them, please help.

Does it look like the stems are rotting at the base? If so, it is caused by the “damping off” fungus. Try watering young seedlings with chamomile tea till they become well established. I mix up 4 cups at a time pouring 4 cups boiling water over 4 tea bags and let it cool to room temperature before watering.

May the force be with you

Hi! Im no expert but just heard about this on the radio. One thing that comes to mind is turning off the heat as soon as the first seedling emerges. The other tip which it sounds like you already follow, is to water when they get a little dry.

I was surprised to hear the advice to turn off the bottom heat as soon as you get a sprout. But it’s worth a try!

quote: Originally posted by Brian Hy:
I water with rain water and a 10-52-10 mix to help them start and I use Supersoil for soil.

You’re not fertilizing two week old seedlings are you? Otherwise it sounds like damping off. Were you using clean trays and fresh mix? Did you have the trays covered?

i would say its damping off also.
the only time i had that problem was when i used rain water!
now i always use tap water for my seedlings, i hold back with the rain water until they get bigger.
also i never feed my seedlings till a week or so after ive transplanted them.

With damping off, the plants tend to rot off at ground level and fall over. It seems like these are actually wilting while they are still standing. Can you clarify this please Brian.
If it is damping off, it’s a fungal problem and can be overcome by adding some condies crystals to water until the water is just slightly pink, then spray the surface with a misting spray.
I only ever feed seedlings with a half strength mix of fish emulsion fertiliser and i start them in a sand/coir/worm casting mix.

The secret is the soil.

The light is also too high. The florescents should be kept no more than 2 inches above the seedlings. Otherwise they are going to stretch and get thin stems that can cause them to fall over also.

and maybe this will help a lil.

I’ve just started some tomato seeds thats sprouted over the last few days.They sit in my kitchen window(east lighting)Humidity is always high in the kitchen.I doubt my soil temp was very high.being its been in the 80s out I’d guess my soils in the 70s.As to pepper seeds.I’ve always sown direct into a pot and keept in sunny spot in yard till sprouted then moved to bright shade.I’ve never been able to get um started indoors so am no help there.I know they never took me 100 days to sprout.I’d guess more 2-3 weeks.(and being I soweed them friday. I’ll count this time)

I will age ungracefully until I become an old woman in a small garden..doing whatever the Hell I want!

OK, so the stems are strong, this rules out damping off. There’s nothing wrong with rainwater, unless you are in a high air pollution area or an acid rain area. I’m thinking fertilizer burn or soil temperature. The wilting is what happens to plants that are getting way too much N. Though the fert you’re using is extremely high in P, so that’s not necessarily the problem. The symptoms would be different. (Thinking out loud here)
My other suggestion is the temperature of the soil and i just did a conversion to celsius (which i use) and it’s pretty damn hot. Like, it’s the temperature of the air at midday in summer. Way too hot for the root system i reckon. Yeah, i’m sold on it. Turn off or turn down the heat and i’m certain your problems will end. BTW, a temp of 15 deg Celsius (60 F)is plenty to germinate the most warmth loving of seeds, like corn and pumpkin, so i don’t reckon you need to have the temp set so high to get that germination rate. Maybe get it down to about max 70 deg F.

The secret is the soil.

My peppers were slower to germinate because my apartment is around 70*F so the soil temp is lower than that but they do germinate and grow to adulthood. I just put them in regular potting soil in a planter and keep the soil moist. Nothing fancy at all and they do fine. It seems like the more care I lavish on a seedling the less chance it has of surviving lol.

What kind of pepper takes 100 days to germinate? I think you’ve been sold a bill of goods. I’d go with a standard potting mix or a custom one like Longy’s, homemade. And get the heat way down, and don’t worry about fertilizing seedlings. And rig a way to move your lights. flourescents won’t burn even if they’re touching, get them as close as possible.

Even my growlights are getting restless!

I did peppers too and mine are finely peeking thro’ after 9 days, I was prepared for this, my instructions said at least 7 – 14 days.

I also used flor. lights but keep the seeds cover with newspaper until they sprout thro’. Using the lights more for heat the first few days.

For this “New Year” help me to be kinder and more loving to all around me, I pray.

quote: Sounds like you are baking those seedlings

I couldn’t agree more! Seeds only need that heat to germinate. once they’ve sprouted, they prefer cooler temps.
I am one that does not save any money with heating bills in the winter. I’m always freezing so that heat is cranked! But the room where I keep my seedlings, I have the vents closed, the window cracked and a fan circulating air at all times.

From The Garden Forum: I don’t get it… My seedlings start fine and then die in a couple of weeks. I am mostly trying to start peppers but have a bunch of other stuff too.I have a cabinet that I made into a seed starting