How to avoid damping off in cannabis seedlings

Published Aug 10, 2021 01:00 p.m. ET
iStock / Yarygin

There is nothing worse than investing your hard-earned cash into cannabis seeds that get you all excited when they sprout, only to die off suddenly afterward with no apparent cause or reason. It can be devastating, especially if you’re germinating seeds that need to be ready for transplanting once the weather outside cooperates, because by this point, you’ll have lost precious time and energy, and there’s no going back. Instead of dealing with the disappointment of losing a batch to the dreaded damping off, it’s best to do everything you can to avoid it.

What is damping off?

Damping off is a disease or condition that can occur in cannabis seedlings, and it’s generally caused by one of several different pathogens that can suck the life out of your plants at their most fragile stage. In some cases, perfectly healthy-looking cannabis seedlings will suddenly double over, looking deflated, a process that can happen as quickly as overnight, but there are often signs and symptoms well before their ultimate demise. Droopy leaves, softs stems, and discoloring can all be caused by damping off.

When does it happen?

Since damping off is essentially a type of root rot, it can technically happen at any point during these plant's growth, but this condition most commonly impacts cannabis seedlings shortly after germination is complete. This is when the root system is at its weakest, rendering the fresh sprout vulnerable to attack. It’s also most prevalent in cool, wet environments.

Why does it happen?

Damping off is caused by different types of mould or fungus that thrive in damp, cool conditions. Unfortunately, it infects the plant from beneath the soil, in some cases hitching a ride in on the seeds you planted. Once so much of the roots are impacted, it doesn’t take long for a die-off to occur because then there is no longer any way for the seedlings to absorb essential nutrients or water which is absolutely necessary for their survival.

How to identify damping off

For beginner growers, it can be difficult to tell whether or not such a small cannabis plant is truly in good health, but there are some specific symptoms to look out for if you’re worried:

  • Seedlings never make it through the soil

  • Stems and cotyledons (the first leaves) may be soft and feel drenched in moisture

  • Extraordinarily thin stems

  • Discoloured stems or leaves

  • Wilted leaves

  • Roots aren’t forming

  • Fluffy, white webbing on any part of the plant (often occurs in plants that are kept in high humidity)

How to avoid it

Damping off can happen to anyone, regardless of how careful growers might be. Still, there are more than a few ways to prevent this condition from ever starting, and if you use all of them, good luck will lean more in your favor for future crops.

  1. Sterilize everything from pots to tools that you’ll be using

  2. Use only new, high-quality soil

  3. Store all tools (trimmers, shovels, gloves, etc.) in a clean environment between uses

  4. Heat trays of soil to 70°F-75°F using an electric heating pad/blanket

  5. Wait for the right temperatures to grow

  6. Potting mixes with good drainage should help you to avoid this problem

  7. Always use fresh, clean water to nourish your cannabis seedlings

  8. Maintain 13-16 hours of light using soft fluorescent grow lights

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