Seedling Damping Off

Seedling damping off picSeedling damping off – the bane of gardeners and seed starters everywhere. It attacks our seeds and our little seedlings, killing them before they can mature enough to be transplanted outside. I’ve seen it in my trays here and there over the past few years, but this year I have an epidemic, it seems. I’m going to have to start all over again with much of my seed.


Damping off is the term used for a variety of fungal pathogens that attack before and after germination. These fungi survive well in soil and plant debris and thrive in wet, cool conditions. The fungi either kill the seed before it germinates or attacks the young stems and leaves of new seedlings. It is recognizable as tan, mushy spots or pinched, rotted stems (called “wire stem” – see picture above); and it will cause the complete collapse of the seedling. Once a plant has mature leaves and a good root system, it is able to fend off these fungi and survive.

My squash, pumpkins, and melons have germinated rather well; and almost all of them now have two or three mature leaves. I did lose a couple of watermelon, and one of my squash as it was coming out of the seed.

Damping off of Black Futsu squash seedling

Damping off of Black Futsu squash seedling

However, overall, the cucurbits are doing well compared to my nightshades. I have about 25% germination rate in my tomatoes, and about 10% in my peppers. I’ve lost several peppers that did germinate, and a couple of my tomatoes never got past the “poking out of the soil” stage.

Damping off in Lemon Drop peppers

Damping off of Lemon Drop peppers


There really is no “cure” for damping off, so the only remedy is to try to prevent it. I thought I was doing well towards that end, but it appears that the couple of mistakes I made were enough. šŸ˜¦


  • Use new, unopened (sterile) germination mix to plant in.
  • Use germination mats under your seedling trays. The heat gives the seeds warmth to germinate and helps to prevent damping off fungi. (The fungi likes cool environments.)
  • Use new pots and trays, OR sterilize used pots and trays in a 10% bleach solution for 30 minutes. (I use new seedling inserts but reuse my trays. I didn’t think about fungi possibly being in the trays and wicking up into the drainage holes of my inserts, so I didn’t sterilize the trays. MISTAKE #1)
  • Keep the germination mix and seedlings moist with lukewarm clean water. (I didn’t always check to see if the water in my watering can was warm enough. MISTAKE #2.)
  • Grow your seedlings in an area with good air circulation and plentiful light.
  • Sprinkle the top of your germination mix with cinnamon; I’ve read that it helps fight the fungi. I figure, it can’t hurt, so I’ll try it.


  • Do not reuse pots or trays without first sterilizing them, as mentioned above.
  • Do not water seedlings with cold water.
  • Do not overwater or let seedlings sit in water. (I think a few times, I added too much water in the trays under the inserts, and the germination mix got too damp. MISTAKE #3.)
  • Do not grow seedlings in a cold room (such as an unheated garage or basement).
  • Do not grow seedlings in low light conditions.
  • Do not over-fertilize seedlings with nitrogen.

I have four weeks or so before last frost, so I am now a month behind schedule – again. Last year, it was using the wrong soil. (Read “Germination Failure” from last year.) This year, it’s damping off. To be honest, I was so tempted to throw my hands up and forget it all this year. I’ve run out of seed for some varieties (and would have to order more ASAP), I have to sterilize the trays and use more new inserts, and I have to replant. I wouldn’t even have my seed for another week. Planting would be delayed until the end of April instead of the end of March. Is it worth it??

Well, I can’t get 14 varieties of peppers and 8 varieties of tomatoes from the local nursery. Even what IĀ  could get would cost me $4 a plant! Plus, we do have a very long growing season here. What’s another few weeks delay? The choice is either start again or go without tomatoes and peppers in the garden.

Hmm…put that way, it’s a no-brainer. Now please excuse me. I need to go order more seed and sterilize some trays. I have more planting to do!

UPDATE: To learn about a great way to germinate pepper and tomato seedlings, click here.



2 comments on “Seedling Damping Off

  1. So sorry to read about your damping off problems. I think you are wise to replant. Plants often seem to catch up when planted later. I used the Jiffy brand seed starter soil from Lowes and my seedlings seem to love it. Good luck!

    • I use Gardener’s Supply germination mix, and it’s wonderful. I just made a few mistakes that I think contributed to the problem. I was trying to be wise and water from the bottom – to keep the damping off fungi at bay – and obviously added to much. I think I underestimated the power of the peat in the mix to wick up the water! Well, at least we have a long growing season and I don’t have to worry about not having time to harvest before frost; it just may be a few more weeks before my first tomatoes and peppers. (Like that’s not bad enough, huh? LOL)

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