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You carefully sow seeds into perfectly moistened soil. You check them seven times a day until the first green sprout arches its way above the soil. Ooh, the excitement as tiny green leaves unfurl and seedlings grow taller. Then, suddenly, disaster! The bushels of tomatoes and bouquets of flowers dancing in your head have been wiped out in an instant by The Dreaded Damping-Off. What is it, and how can you prevent it?
Damping-off is a term used for a variety of fungal problems that lead to sudden seedling death. [1] Beginners and experienced gardeners alike are frustrated and disheartened when it strikes. The pathogens attack the tender stems and roots of the seedlings. Some seedlings look pinched at the base of the stem, others flop over, and some wither away entirely. Once the process is underway, it’s hard to save even a few of your plants. Prevention is the best cure.
Sterilize
Sterilizing your seed starting mix reduces fungal spores and other troublemakers. Commercial seed starting mix isn’t necessarily sterile, especially once the bag has been opened. You can sterilize potting mix in the oven, using pans or roasting bags with a thermometer to monitor internal temperature. Veteran seed starter Weezingreens advises heating the mix in a 200 degree (F) oven to an internal temperature of 180-200 degrees (F) for 30 minutes [2]. Baking potting mix does have a certain odor that many people (or their spouses) object to.
I like using the microwave. I discovered the hard way that the potting mix must be moist [3]. Add 1 cup of water per quart or two of dry, soil-less mix. Work out any lumps or chunks of compressed mix. Additions such as moisture crystals, extra perlite, and time-release fertilizer pellets can be mixed in before microwaving. Put the mix into a microwave safe container with lid. I put my mix into a huge Tupperware bowl that holds nearly 2 gallons, but any microwave safe container with a lid will work.
Cover loosely, and microwave on high for 8 to 12 minutes, until you see steam condensing in droplets on the underside of the lid. Close the lid tightly and allow the mix to steam at least 10 more minutes as the mix begins to cool. Steaming the potting mix also seems to “open up” the peat moss or coir so it absorbs water more readily. Although it won’t be strictly sterile once you start fooling with it, unused mix can be sealed up for later use.
Put that sterile potting mix into clean planting containers. If you’re reusing containers, clean them first with soapy water and bleach.
Less water, more air
Wet conditions can promote damping off. Don't overwater. Keeping your potting mix barely moist rather than soggy is essential to healthy seedlings. If you water from the top, water between rows of seedlings and try not to drench the tops of the plants. Bottom watering seems to help by keeping the soil surface a bit drier, also. Pour water into a tray containing the seedling pots, and let them soak up as much as they can through the holes in the bottom of the pots. After 15 minutes, pour off any excess so plants don't sit in water. Good air circulation helps prevent damping off. I’m always tempted to cram as many plants as possible onto my light shelves, but overcrowding limits air flow. A fan placed near your plants helps to keep the air moving.
Many people recommend removing germination domes and other covers as soon as seeds germinate or doing without covers altogether. I put lots of little ventilation holes in the plastic domes for my trays. The holes allow some air flow and keep the humidity from getting too high. I do remove the domes once seedlings have several sturdy sets of leaves.
Anti-fungal agents
Watering or misting seedlings with an antifungal solution will also help protect your seedlings. One tablespoon of 3% hydrogen peroxide per quart of water is sufficient. You can also brew strong chamomile tea and add an ounce or two per quart of water.
A one-time dusting of cinnamon or powdered charcoal on the soil surface can also be used as an antifungal agent. Adding a top layer of chopped sphagnum moss, sand, or chick grit may help discourage fungi from growing on the surface of your potting mix. If you have persistent problems with damping off, you may need to consider a chemical control such as Captan, but such measures shouldn’t be necessary for most home growers. Sterilize your seed starting mix. Minimize wet conditions, and maximize air flow. Add an anti-fungal agent to your water. These steps will go a long way toward preventing the Dreaded Damping Off, and you’ll have healthy seedlings to set out this spring!
[1] Tom Clothier's Garden Site has some excellent information and advice about damping off. See his Damping-off FAQ page.
[2] Weezingreens is a DGer from Alaska who starts thousands of seedlings in her basement each year. She gives excellent advice in the DG Propagation Forum (subscribers only), on this damping off thread and elsewhere.
[3] If you'd like a laugh, click on the link to my Fire in the Hole! thread in the Propagation Forum.
About Jill M. Nicolaus
Better known as "Critter" on DG, Jill gardens in Frederick, MD. My irises are bloomed out, but the daylilies are just getting started! Our front porch robins are busy fetching worms for their second crop of babies. I love summer!
(Images in my articles are from my photos, unless otherwise credited.)
Posted by Dominican (from Tupper Lake, NY) on June 06, 2009 at 02:20 PM:
I build a mini greenhouse from windows that were going to the dump. Its a bit late but I can still finish it and tune it up for next season. I will post pictures when I am done with it. thanks to all your great ideas, David
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Posted by critterologist (from Frederick, MD) on June 06, 2009 at 06:11 PM:
Fantastic! You may be able to use it to extend your growing season this fall, too, or to overwinter more tender plants.
I hope you'll decide to subscribe to DG... among other things, you'd be able to read threads and post responses in the Greenhouse Forum. :-)
I'm looking forward to seeing photos!
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Subject: Newbie here with a few questions
Posted by Berrywrap (from Philadelphia, PA) on April 10, 2008 at 01:38 PM:
I have started my first seedlings in 2" peat pots. I planted tomatoes, nasturtiums, viola tricolor (johnny jump ups) bush morning glory and forget-me-nots (pretty ambitious for a newbie eh? : ). I started my seedlings indoors and I have had 98% success in seed germination. Just to be clear, I live in Philadelphia (zone 6) and do not have a garden, but have been successful over the past year with container gardening. I planted a tomato plant last year and it did extremely well. For a container plant it gave us months of tomatoes. However, with seedlings I am unsure. I think I may have put too many seeds in each peat pot. I have been successful so far in separating some of the tomatoes and the transplants are thriving in their individual peat pot. How long should I wait before I transplant them outside? I have seen pictures where the stalks are thick and green, however, my tomato seedlings are thin and only have two leaves. They are about 5 weeks old. Am I asking for too much to fast? Should young seedlings be feed? The seed packet did not give me much help except to say that I should thin them out when they are about two inches tall (check) and that they harvest in 65 days.
On another note, I have had a few stems that have fallen over and one or two that appears as if it was snipped at the soil line. The other seedlings still look healthy. How will I know if they are suffering from damping off? Any help anyone could provide me would be greatful. I will take some pictures and upload them later today.
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Posted by critterologist (from Frederick, MD) on April 10, 2008 at 02:11 PM:
Welcome to DG! Have you found your way over to the "Beginner" forums? If you were a subscriber, I'd also direct you over to the tomato and veggie forums... and I hope you'll decide you like DG well enough to try a subscription at some point, because you'll be amazed at how much more is here!
I start tomatoes in shallow trays of potting mix, in rows spaced only an inch apart, and then I transplant them once they get their first "true" leaves (the very first leaves that seeds sprout are "cotyledons" or nurse leaves). Except that I transplant them singly rather than in clumps like basil and some others, I start tomatoes very similarly to the way I describe in my "Seed Starting 101: Sowing and Transplanting" article.
At 5 weeks old, your seedlings should have more than 2 leaves. I don't fertilize tomato seedlings until I plant them out, so I don't think that's the problem. What are you doing for light? I'm guessing that might be the issue. Please check out "Seed Starting 101: Setting up Light Shelves."
As you can see, I've been writing a series of seed starting articles this year... you can click on the link at the bottom of the above article to see a list of all the articles I've written. I think the "Seed Starting" articles might be helpful to you. Today's article was on hardening off your seedlings -- very important before you put them out next month! -- and next Thursday there will be an article with some transplanting tips.
The ones that have fallen over or been "snipped" at the soil line have probably damped off... following the suggestions in this article should help (fan, bottom watering, hydrogen peroxide or chamomile tea, etc.).
Good luck, and have fun!
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Posted by Berrywrap (from Philadelphia, PA) on April 11, 2008 at 03:19 PM:
Thank you very much for the advice. I will be looking for those articles! I do not have a direct light source as they are in the kitchen window sill. Luckly I get full sun in that part of the house and the back deck. I am looking to get one of the shelf lamps suggested, but there are so many to choose from. I will go to the beginners section and see what others recommend.
Thanks again!
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Posted by critterologist (from Frederick, MD) on April 11, 2008 at 04:10 PM:
You're welcome!
Windowsill light is never as bright as it seems to us... I was amazed at the difference when I started growing under lights. An inexpensive shop light fixture with cool fluorescent bulbs will be just fine for seedlings -- no need to shell out the bucks for fancy "grow lights." :-)
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Subject: A timely article
Posted by pamsaplantin (from Morgantown, WV) on March 03, 2008 at 03:21 AM:
I was thrilled to find stevia seeds at my local Target store a few weeks ago. I rushed home, filled a nice pot with regular potting soil, planted half my sparse treasure, watered, covered lightly & put it all on the seedling heat mat. A week later, I had a pot full of grungus with one tiny frail seedling trying to make its way upward. I remembered your suggestion about the ground cinnamon & sprinkled it around the invalid knowing in my heart that it was futile. Two days later he, too, was gone.
Now, I have reread your article & when I start over I will begin with sterilized soil!!!! I had a good bit of trouble with damping off last year but nothing like this. I used a reputable brand of potting soil, so I just didn't believe it could make that much difference. The heating mat is new & I suspect that may be what made the situation so nasty, so fast. Anyway, I truly appreciate your article. Thanks!!
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Posted by critterologist (from Frederick, MD) on March 03, 2008 at 03:59 AM:
You're welcome... but FYI, the problem may not have had much to do with your technique... Stevia can be really tricky to germinate. Even with fresh seed sent by a friend, I don't think I got better than 10% germination. The little seedlings sit there forever looking tiny and frail before they finally get enough of a root system to take off. Bottom heat will definitely help germinate Stevia... and you might even try pre-sprouting the seed between layers of damp paper towel in a baggie.
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Posted by pamsaplantin (from Morgantown, WV) on March 03, 2008 at 08:45 PM:
Thanks for that info. I won't dump the pot just yet but almost the entire surface of the soil has white "stuff" growing on it. Mold? Fungus? Who knows. I was sick. I don't believe I over watered. I just don't know what went wrong, but sterilization would surely have to help whatever it is. I invested in some chick grit today & I'm getting ready to microwave some soil in a little while. It may have been a good thing that it happened now with just one type of seed instead of later when I start the bulk of my seeds for the garden. Lesson learned! And I'm very glad I saved half of the seed as a backup.
About sprouting seeds in a baggie - can you tell me how you do that? I've had people tell me they do that, but the one time I tried it, the seeds just got slimy & smelly. I assume the bag has to stay open but is there anything else I need to know?
Thanks!
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Posted by critterologist (from Frederick, MD) on March 03, 2008 at 11:54 PM:
I don't think I've ever had seeds get slimy with the baggie method, hmm. You could probably add a few drops of hydrogen peroxide to the water (keep in mind the 1 tablespoon per quart ratio used for watering seedlings) that you use to moisten the paper towel -- couldn't hurt. The paper towel or coffee filter shouldn't be dripping wet; wring it out pretty well. Put the seeds between two layers of damp paper towel, then put the paper towel into a baggie. I do seal the baggie, but I puff a little air into it first (although I couldn't tell you the rationale behind that; it's just what I do).
You can hold the baggie up to the light to check for sprouting -- look for little "tails" forming on the seeds.
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Posted by pamsaplantin (from Morgantown, WV) on March 04, 2008 at 02:19 AM:
Thanks! I'll try that.
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Subject: Just what I needed (sob!)
Posted by Fleurs (from Columbia, SC) on February 27, 2008 at 05:21 PM:
Usually a fanatic about winter sowing, I've tried getting a head start this year with some tender annuals only to discover some ruined plantlettes. Instinctively, I removed the humidity dome and won't replace it until I've made some holes in it. I'll also try the hydrogen peroxide solution.
One question: once a few seeds have succumbed to damping off, will the other little cells be okay? (Please say "Yes").
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Posted by critterologist (from Frederick, MD) on February 27, 2008 at 05:55 PM:
It's hard to say for sure without knowing if your potting mix has a pathogen issue... but I am guessing that your problem had more to do with overly wet/humid conditions. I'm glad you didn't lose all of your seedlings!
Once germination has occurred, most seedlings don't seem to need the extra protection of a humidity dome (with or without holes). Since you've already encountered problems, I'd suggest trying to do without it, especially once you see germination.
A fan for extra air circulation and bottom watering will also help.
Good luck!
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Posted by Pamgarden (from Central, VA) on March 13, 2008 at 09:17 AM:
Jill, Great article. I should have read all this before I started my seedlings. I was almost afraid to read about damping off, figured if I didn't know about it, I wouldn't worry about it. My little seeds that are up look good (hollyhocks, MG's, basil), but the earliest ones were only planted 3/06/08. I don't have lights. Mine are in the garden room by the south facing windows. I try to turn them a couple times a day so they don't get the major leans. I've grew tomato seeds of heritage types in the past and had almost 100% germination of probably 20 different types in 2" peat pots, transplanted into 4" peat pots. I put them outside before work and took them in again after work for about 30 days. That was the year of my tomato forrest. I didn't do it a second time because it was in the front yard and looked like a jungle. None of the neighbors commented, but I kept expecting to get a letter from the Home Owners Association.
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Posted by critterologist (from Frederick, MD) on March 13, 2008 at 11:57 AM:
I've done the "tomato forest" thing! The past couple of years, I've followed Carolyn's advice and started seeds just 8 weeks before setting out... I only need to put them in 2 inch pots, and they're not so huge and hard to deal with!
Putting them outside on mild days for "real" light is probably even better than using fluorescent lights... but I was stunned at the difference when I switched from windowsill growing to putting seedlings under lights. I thought my window was bright! LOL
Good luck with all your little seedlings!
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Posted by Fleurs (from Columbia, SC) on April 01, 2008 at 01:27 PM:
Wouldn't putting fragile seedlings outdoors for the light burn them instead?
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Posted by critterologist (from Frederick, MD) on April 01, 2008 at 02:39 PM:
You just can't put them into full bright sunlight for 10 hours on their first day out... letting them adapt gradually is the key (aka "hardening off").
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Subject: Thanks so much!
Posted by kd2000 (from toronto, Canada) on February 07, 2008 at 12:41 PM:
Critter thanks so much - I am just getting going on wintersowing and will be sure to use your damp off tips when things (hopefully) start to sprout. Thanks again,.KD
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Posted by critterologist (from Frederick, MD) on February 07, 2008 at 12:54 PM:
With winter sowing, damping off doesn't really seem to be an issue. I think the fungal pathogens can overwhelm the little seedlings in the artificial conditions of indoor seed starting... but outside, the cold or the additional air circulation or something just seems to prevent problems like that.
Yet another reason to try winter sowing! :-)
(See my article on Feb 2 for an introduction, if "winter sowing" sounds like a new but intriguing concept... we have an entire forum devoted to it at DG!)
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Posted by kd2000 (from toronto, Canada) on February 07, 2008 at 03:42 PM:
Thanks Critter:-)) I have actually got about 40 pots in my garage at present and will be putting them out shortly, but a few I am going to half wintersow in an unheated sunroom (japanese maple), so I will be trying your chamomile tea solution. I was wondering should I water indoor seedlings with this solution everytime or once a week, or just once? Thanks again, KD
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Posted by critterologist (from Frederick, MD) on February 07, 2008 at 03:49 PM:
I don't think either chamomile tea or hydrogen peroxide added to the water would ever be a bad thing... it's just a matter of how many times you want to fuss with it. I tend to do it when the seedlings are little, because that seems to be when they're most prone to damping off. After they've been up-potted and are looking sturdy, I make them drink regular water like everybody else (well, sometimes they get a bit of fertilizer, usually at 1/4 strength, but I don't know if I'd recommend that for your maple seedlings).
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Subject: Shelf life
Posted by daylilydaddy (from morehead, KY) on February 07, 2008 at 12:18 PM:
Hey Critter!!
How long do you think the peroxide and water mixture can be stored and still be effective? I know to keep it in a dark colored bottle(since it comes in one, duh), but I know I would not use all of it at one misting and I stagger my seed starting.
THANKS!
George
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Posted by critterologist (from Frederick, MD) on February 07, 2008 at 12:44 PM:
Since the stuff you get at the drugstore is already effectively a diluted solution, I would think you could dilute it further and hold it a while as long as you keep it in a dark bottle as you said... but I don't have a definite answer. I make up strong chamomile tea and keep it in the fridge, then dilute as needed...
I don't really mist my seedlings, but I use the peroxide when I water them when they're little... so I guess I go through the peroxide water a little faster.
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Posted by daylilydaddy (from morehead, KY) on February 07, 2008 at 12:48 PM:
I guess using it for watering would be better than misting since the fungus is in the soil more. Right?
George
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Posted by critterologist (from Frederick, MD) on February 07, 2008 at 12:51 PM:
I also figure I'm more likely to get into trouble with misting because then the foliage is wet -- to me, that seems like it could just invite fungal disease. Big greenhouse growers need to mist to keep humidity levels up, but I don't think we need misting on our little light shelves... at least, not misting works fine for me. :-)
(If you mist and that works for you -- keep doing it! Don't fix it if it isn't broken... there are lots of "right" ways to do things.)
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Posted by daylilydaddy (from morehead, KY) on February 07, 2008 at 12:56 PM:
Makes sense!
THANKS!
George
I forgot to say what a great article. This year I am starting some pretty special seeds for myself and others. In the past I have never had a problem with damping off, but this year I have to be extra cautious.
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Posted by critterologist (from Frederick, MD) on February 07, 2008 at 12:58 PM:
You're welcome... Good luck & have fun with your seedlings!
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Subject: Very good info
Posted by Lindawalkabout (from Holden, MO) on February 07, 2008 at 11:43 AM:
Thanks Critter, I'll be starting my flats soon, been winter sowing (first time WS). I have not had dampening off problems before and never did any pre teatment to flats other then them being new. I think I will do this treament now tho, I don't want to take any more chances. I had heard about the cinnamon dusting and I did that for the first time last year, and all went well .
But I'm going to start some flats under a grow light this season where as I just used the dinning room huge south window, grew thousands of plants, tomatoes and peppers mostly without problems. I'm getting into flowers now so I'm in a new playing field and I want the soil to be safe. So I do thank you for the good information of prevention of dampening off.
Just read your post on your soil in the microwave and you on the phone, and little coals firing up, lol. Sounds like things around here that happen. lol
Hey thanks again , learning more and more and I have veggie garden for many years. That goes to tell ya, never to old to learn more : )
take good care and thanks again, very good artical and thanks for the links as well
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Posted by critterologist (from Frederick, MD) on February 07, 2008 at 11:52 AM:
I'm glad you're enjoying the articles! I think you're going to see a big difference in the sturdiness of your seedlings under the lights (keep the seedlings close to the bulbs). I've never (knock on wood) had a problem with damping-off either, but since it's simple enough to sterilize the soil and add a little peroxide to the water, I figure why not take those precautions. It sounds like your reasoning is about the same.
Happy sowing, and best of luck with your veggies and flowers this year!
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Posted by doccat5 (from Fredericksburg, VA) on February 07, 2008 at 12:03 PM:
Great information, but ain't no way I'm sterilizing soil again. It smells awful.
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Posted by Lindawalkabout (from Holden, MO) on February 07, 2008 at 12:06 PM:
Thank you critter,
You know thinking about my seedlings they have been skinny growing them in the window. So I'm very excited to use the grow lights for the first time. : )
Thanks again and happy growing to you this season.
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Posted by critterologist (from Frederick, MD) on February 07, 2008 at 12:06 PM:
Did you do it in the oven or in the microwave? There's a whiff of scent when I open the lid of the container after sterilizing in the microwave, but it's about 0.01% of the effect of baking it in the oven.
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Posted by doccat5 (from Fredericksburg, VA) on February 07, 2008 at 12:13 PM:
Used the oven, it wasn't pretty.
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Posted by critterologist (from Frederick, MD) on February 07, 2008 at 12:16 PM:
Try the microwave... take it out into the garage if you don't trust me, but try it... or just take the container out into the garage after you seal down the lid (before you open it). I promise it won't stink up the kitchen.
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Posted by doccat5 (from Fredericksburg, VA) on February 07, 2008 at 12:18 PM:
I'll have to find a yard sale microwave, no way I'm using my good one.
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Posted by darius (from So.Appalachian Mtns, VA) on February 07, 2008 at 12:27 PM:
Good article, Jill.
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Posted by critterologist (from Frederick, MD) on February 07, 2008 at 12:49 PM:
Sheesh. Some people have no faith. When you come to the tea party, you can microwave some soil mix, and then you'll see what I'm talking about.
Thanks, Darius!
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Posted by Dea (from Frederick, MD) on February 07, 2008 at 04:47 PM:
Another great article Jill !
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Posted by angele (from Elephant Butte, NM) on February 07, 2008 at 09:03 PM:
Wow! I have had this problem so often. Thanks for a great, informative & simple to apply article.
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Posted by critterologist (from Frederick, MD) on February 07, 2008 at 10:42 PM:
I've learned a lot hanging around DG... this article was mostly about gathering together the info and tips I've come across. (You can tell from that "Fire in the Hole!" thread that there was some trial & error as I learned to apply the information, LOL. ) But a lot of the credit goes to the experts in the propagation forum who answered my questions over the years and posted their own experiences!
Hopefully, you'll be able to ward off the problem and have some sturdy seedlings for your garden this year. Happy sowing!
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Posted by rachel211 (from Springdale, PA) on February 25, 2008 at 07:23 AM:
graat informative article
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Posted by critterologist (from Frederick, MD) on February 25, 2008 at 11:30 AM:
Damping-off is a term used for a variety of fungal problems that lead to sudden seedling death. [1] Beginners and experienced gardeners alike are frustrated and disheartened when it strikes. The pathogens attack the tender stems and roots of the seedlings. Some seedlings look pinched at the base of the stem, others flop over, and some wither away entirely. Once the process is underway, it’s hard to save even a few of your plants. Prevention is the best cure.
