Damping off is a common and devastating disease that affects seedlings in their earliest stages of life. Caused by a variety of soil-borne fungi and water molds—such as Pythium, Rhizoctonia, and Fusarium—this disease can wipe out an entire tray of healthy seedlings overnight.
Damping off refers to the sudden collapse and death of seedlings, typically at the soil line. Affected plants appear water-soaked, soft, or constricted at the stem base. This weakens their ability to hold themselves upright, resulting in a flopped-over appearance.
Damping off disease is caused by fungal pathogens that thrive in overly moist, warm environments. Contributing factors include:
Keep an eye out for these early signs:
Spotting these symptoms early can be the difference between saving your grow and starting over.
Maintain consistent warmth without excess humidity. A reliable heat mat like the Spider Farmer® Seedling Heat Mat ensures root temperatures stay optimal without creating overly moist conditions.
Always sterilize your seedling trays, pots, and tools before planting. This drastically reduces pathogen spread. Use a hydrogen peroxide solution or diluted bleach to disinfect surfaces.
Avoid heavy watering schedules. Let the top layer of soil dry before rewatering. Ensure trays have sufficient drainage holes, and don’t let water pool beneath seedling containers.
Consider sprinkling a light layer of cinnamon powder on top of the soil—it has natural antifungal properties. Chamomile tea and garlic water are also known to reduce fungal populations.
Soilless growing mediums with added biofungicides can give you an upper hand. Pro-Mix HP with Biofungicide + Mycorrhizae is one of the top recommendations for those seeking pathogen-resistant media from the start.
Remember: prevention is always easier than recovery when it comes to damping off.
Want to learn more about hydro growing techniques? Check out our guide on What Are Hydroponic Systems and How Do They Work?
