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Reading time: approx. 10 min.
- Yellow Leaves – Early warning signs & fixes
- Light Stress in Seedlings – Symptoms & relief
- Overwatering vs. Underwatering – Diagnose & correct
- Deficiencies – What to do about weak growth?
- Cannabis Seedling: 1 Week Old – Care tips & issues
Damping off is a nightmare for cannabis growers: it strikes seedlings and young plants—often suddenly, usually fatally. In this guide, you'll learn the causes, warning signs, and every quick fix to save your crop. Packed with practice-proven tips, expert advice, and modern prevention strategies.
What is Damping Off?
Damping off is a fungal disease that kills seedlings within days. The culprits: soil fungi like Pythium, Phytophthora, Fusarium, and Rhizoctonia. They attack the roots and stem base, causing seedlings to lose support, collapse, and usually die for good.
Causes: Why does damping off occur?
- Overwatering: Constantly wet substrate is a fungus magnet.
- Poor drainage: Pots without drainage holes cause root rot.
- High humidity & low temperature: The perfect climate for fungal spores.
- Old or contaminated soil: Pre-infected soil brings the fungi with it.
- Contaminated seeds: Low-quality seeds increase the risk dramatically.
- Seedling stress: Temperature fluctuations, light stress, or nutrient issues make seedlings more vulnerable.
Recognizing Symptoms: Early warning signs
- Limp, wilting leaves
- Soft, discolored stem (brown, black, thin)
- Seedling topples over or can't stand upright
- White or gray mold on the soil surface
- Rotten or blackened roots (visible if checked)
Infographic: Healthy vs. infected seedling (damping off)
Check: Healthy vs. infected seedling
- Strong, upright
- White root system
- Firm stem
- Limp, brown/black stem
- Mushy roots
- Moldy soil
Quick Actions: What to do if damping off strikes?
- Isolate the affected seedling—stop watering!
- Remove the top layer of soil and replace with fresh, dry substrate.
- Increase ventilation, reduce humidity.
- Dispose of all infected plant material and soil safely.
- Optionally: Use mycorrhizae/trichoderma products for remaining plants.
Prevention & Treatment: How to protect your seedlings
- Always keep the substrate moist, never wet!
- Disinfect pots & equipment before use
- Use only high-quality soil & seeds
- Don't keep seedlings covered for too long—ensure fresh air flow
- Keep humidity at max. 60–70%, temperature at 20–25 °C (68–77 °F)
- Let the soil dry slightly between waterings
- Optionally: Build up biological protection with trichoderma/mycorrhiza
Mark’s expert tip: “Less is more: waterlogging is the main enemy! Always check the soil and moisture before watering. Don’t plant seedlings too deep.”
FAQ: Frequently asked questions about damping off
Damping off can destroy your whole grow within days. But with the right quick actions, clean equipment, and smart watering habits, your seedlings stay healthy and strong. Better to water less and check more often!
Still have questions? Ask directly on Reddit with the Cannoptikum Crew or leave a comment!