Damping Off Marijuana Seedlings

Damping off is a sort of reaction that your marijuana plant has to a disease. It most commonly occurs when roots, seeds, or seedlings undergo an attack from fungi that formed in soil.

This attack stops the upward movement of nutrients, making your marijuana plant is not receiving a proper distribution of nutrients. Because of this unequal distribution, the stem develops portions that are soft and mushy, making the plant eventually topple over and die.

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    Fungi (such as Rhizoctonia and Pythium) grow best in moist, warm soil that has a high concentration of nitrogen. Pythium creates spores, but Rhizoctonia do not – instead, they are parasitic pathogens that are asexual and cause disease in plants.

    Damping off typically starts right under the soil line. As a grower, you probably won’t even notice a problem until you see atrophy in the stalk and lower leaves of your marijuana plant. You will also notice discoloration of the section of the stalk that is closest to the base. This discoloration usually takes the form of a yellow or brownish color.

    You will also start to see lesions between the nodes, which will darken into red-brown cankers. After a while, the entire stem will become soft and brown, and the plant will collapse. This can kill off the marijuana plant since it needs nutrition to stay standing up sturdily.

    Like many problems, damping off will affect young, tender seedlings before it gets to your mature plants. It will first resemble an overwatering problem because of wilting, but you will know it’s a reaction to fungi once you start seeing lesions on the upper section of the plant.

    Not sure if your marijuana plants suffer from a damping off infection? Check the article Marijuana diseases for a list with pictures of all possible marijuana diseases.

    How to fix the problem

    As with most conditions that can affect your marijuana plants, proactive prevention is the best way to go. Keeping close control of moisture levels is the best way to avoid damping off from ever becoming a problem. If your soil is wet, your plant will have “wet feet,” which can eventually ruin your marijuana garden. Don’t water your plants unless the top layer of soil is dry.

    If you live in a place with frequent rains (or it happens to be a particularly rainy year), you can prevent the soil from becoming saturated with water by ensuring that the soil drains well. This will keep water from pooling where the roots are located. When preparing your soil, you can begin by putting in perlite or vermiculite with your soil mix. This will allow for more airflow.

    How to fix the problem - ensure the soil drains well

    If you are growing your crop all the way from seed, you should be extra careful about where those seeds come from. They need to be completely free of disease. Don’t plant them too low – about one-fourth of an inch deep should be good. This helps with damping out because moisture is present in higher amounts the lower underground you go.

    It’s a good idea to also start growing your seedlings indoors, or in containers of some sort. Then, at least one week before you transplant the plants to an outdoor grow site, combine cured compost (which has beneficial bacteria) with the soil. Don’t transplant the seedlings until they have grown at least a few sets of leaves. This will ensure they will be strong enough to handle the transplant.

    Transplant seedlings until they have a few leaves
    Transplant seedlings only when they have grown a few leaves

    If you want to be extra careful about avoiding damping off, spray the soil with an anti-fungal treatment made from copper, chamomile tea, or garlic oil. Let it dry. Additionally, ensure that all your tools are disease-free by sterilizing them after each use. This will help prevent the spreading of any fungi or diseases that have found their way to one of your plants.

    If you do have seedlings that are exhibiting signs of damping off, you probably won’t be able to save them. More mature plants do have a chance of being saved, however. Try removing the parts of the plant that have been affected, and then use diluted hydrogen peroxide to apply to the wounds. If the cankers that appeared on the stems are particularly severe, try spraying them with copper fungicide, clove oil, coriander oil, or sesame oil.

    Marijuana plant symptoms

    Plant symptoms:

    • Atrophy in stalk
    • Stem discoloration (yellow-brown) near base
    • Stem lesions (between nodes)
    • Red-brown cankers between nodes
    • Stem browning and softening
    • Plant falling over
    • Plant death
    • Lesions on upper portion of plant
    • Wilting

    Leaf symptoms:

    • Atrophy in lower leaves
    • Wilting

    The best way to avoid damping off is dedicating the time and effort to giving your plants a strong basis for healthy growth. Pay attention to moisture, nutrients, sunlight, and every other element to makes sure they are able to reach a mature age without succumbing to damping off.

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    FAQs About Damping off Cannabis Seedlings

    What are some common signs of marijuana seedlings that are damping off?

    Among the most common signs of damping off are browning and softening of stems, lesions, and wilting of leaves.

    How do you fix damping off seedlings on weed?

    Controlling moisture levels, making sure your seeds are free of diseases, and spraying the soil with anti-fungal treatment are some ways to treat damping off weed seedlings.

    Have you dealt with marijuana seedlings that are damping off? Please leave comments or questions below!

    Happy growing!


    Robert Bergman

    Robert Bergman is an Amsterdam-based marijuana grow expert who has years of experience from small grows to massive operations. His passion for growing lead him to develop his own Gold Leaf strain. Now, Robert is dedicated to sharing his knowledge with the world.... [Read full bio]


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      21 comments on “Damping Off Marijuana Seedlings”

      1. I think I am having problems with seedlings dumping off before they sprout through the soil. They have a nice route but never pop up. I spray lightly twice a day or sometimes once a day and I am using jiffy peat pots. Any suggestions?

      2. For seedlings that exhibit “damping off” you could cut the plant where you see the thinning area and treat as a clone and re root it if the seedling means that much to you I have done this on hard to get/expensive seeds

      3. Thanks a lot guys I’ve lost a lot of seedlings this year couldn’t figure it out I bought my genetics from you so I know that wasn’t the problem cause all these years I’ve had no problems so I’ve tried changing soil and everything I dig up the natural soil and fill the wholes with my soil wish knew this info sooner thank you so much I love you guys

      4. I recently purchased a pot for pot and 5 Girl Scout cookies extreme auto flowering seeds. Followed the instructions. Everything was going well until 3 days after transplanting. Now I have signs of damping off. No lesions on the leafs. A little browning where the stalk went limp. Sprayed some sesame oil directly to the stalk then lightly misted leaves with diluted neem oil, dish soap, and water mixture. Using loose soil I was able to push up the plant so it doesn’t lean. Any other suggestions? This is in a separate planter but near a lemon tree.

      5. Jessi, You need to join our forum where experts and friendly members can help guide you from start to finish. Go here: support.ilovegrowingmarijuana.com

      6. In need for serious help. I recently just mixed a coco coir soil medium for my seedlings and I the past two months I have had over 50 seedlings damp off. I have tried several different things including a fungicide to try to stop this and nothing has worked. I mixed the coco coir fresh the soil is not too moist even at times they then end up drying up. I Sterilized the coco coir twice since initially mixing it. They get alot of light. There has not been any fungus growth that I have seen. All the containers used were all sterilized….

      7. The best organic solution to damping off is to use NoDampOff, which is milled sphagnum. The product controls over-watering and naturally resists the bacteria that causes damping off. It has been used for over 50 years by professional horticulturists and by the USDA. It should work on cannabis.

      8. Alex,

        Seedlings should be paced under a T5 lamp with fluorescent tubes 1-2″ above the seedlings. This promotes tight nodal spacing and does not allow the plant to stretch looking for light, thus weakening the stem.

        Sounds like they died from not being watered. I do not use a dome on seedlings; I only use a dome for cloning operations 🙂

        Hope this helps

      9. HELP! I’ve been soaking my seedlings in water till the tap root breaks through, then putting them into Rapid Rooters on a tray with a heating pad & humidity dome. I’ve had good success in the past with them popping up and going into Seedling stage, but this weekend I just lost almost ALL of my plants and I’m not sure why. I have a few theories but would love some advice.
        1. Did I keep the humidity dome on too long without direct light? The light was 3 or 4 feet up above the dome on 18/6. The stalks were tall and thin, then bent over and died indicating stretching.
        2. I overwatered? Because they wilted and died under the dome I thought that might be the case, but the rooters were totally dry so it would seem maybe they were under-watered?
        Ugh. I’ve done 4 successful harvests but now I feel like I can’t repeat this beginnin process very well.

      10. i am using rapid rooter plugs for my cuttings and was wondering do i need to use any type of nuts for them or just what is in the rapid rooter cubes

      11. A tiny pinch of cinnamon lightly sprinkled with kill the fungus that causes Damping off and it is organic. Just don’t over do it.

      12. […] Again, preventative care is the only real way to deal with damping off and other fungal disease-related problems. Usually, plants won’t be able to bounce back from damping off, and so it’s up to the grower to prevent it from happening in the first place. Read more about Damping off on marijuana seedlings […]

      13. The easiest and best way to prevent damping off is by using NoDampOff, which is milled Sphagnum Moss. Mosser Lee has been selling to gardeners and nurseries for over 80 years. Studies confirm that this product really works.

      14. […] Again, preventative care is the only real way to deal with damping off and other fungal disease-related problems. Usually, plants won’t be able to bounce back from damping off, and so it’s up to the grower to prevent it from happening in the first place. Read more about Damping off on marijuana seedlings […]

      15. My question was answerd about damping off never did I think it started as a seedling all plants died really messed with pocket book now screwed thank u for this site I will order more seeds from u and try again so pissed though they were looking fantastic thought was going to reep rewards was so excited till they started turning brown and stem damage leaves falling off lost a lot of money didn’t have now have u to fall back on for problems thanks so much for info Rodney-HP

      16. Hi, I am new to this but if you can help me I will order all of my future seeds through your ads. I have 30 seedling that have just popped up. They are in rockwool cubes with poland spring water with a ppm of 45 mixed with a small dose of general hydroponics rapid start (up to around 60 ppm.) The seedlings have just sprouted but some look a little brown to me. I am running 5 auto amnesia autoflowers, 10 thc bombs and 10 tch cluster bombs. The autos are green amd look healthier but the thc bomb strains look kinda brown and sickly. I was wondering if this was normal this early in development. They were planted four days ago amd are still babies but one of the autos looks bright green and already has a tap root protruding from the bottom pf the rockwool. Is it just advanced or are the other seedlings slow. Should I use any nutes at all this early and if so which ones? I have the full cyco line. Also I am using a homemade15 site undercurrent system with 13 gallon buckets, 2 alita 80 lpm pumps and a 1200 gph pump, if that makes any difference. The autos are going in regular bubble buckets.