How do I prevent mold in microgreens?
Written by
Benjamin Miller
Reviewed by
Prof. Samuel Fitzgerald, Ph.D.To prevent mold in microgreens, it is helpful to understand the conditions that are most conducive to mold growth. Excess moisture and poor airflow create the best breeding ground for mold. To remedy this, I employ three basic methods that have all been developed through trial and error. These methods will keep your greens protected from harsh chemicals.
Bottom-Watering System
- Place trays in shallow water reservoirs allowing upward moisture absorption
- Keep soil surface completely dry depriving mold of germination sites
- Use trays with ¼-inch drainage holes for controlled water access
Airflow Management
- Position oscillating fans 3 feet from trays for gentle air movement
- Run fans 4 hours daily during daylight growth periods
- Avoid direct strong airflow that can dehydrate young seedlings
Moisture Monitoring
- Check soil daily using the knuckle test insert to first joint
- Maintain sponge-damp consistency never soggy or crusty dry
- Adjust watering frequency based on ambient room humidity
Use bottom-watering as your first line of defense against mold. This will keep the top surfaces of the soil dry while still providing hydration to the roots. I use old baking sheets as reservoirs of water under my trays. I only fill them up to half an inch of water when the soil feels dry underneath the surface.
Strategically manage air circulation to interrupt mold. Mild air movement will help alleviate any stagnant humidity pockets around the plants. My personal setup includes small USB fans on timers, positioned to produce a cross breeze without directly blowing onto delicate seedlings.
Become an expert at moisture monitoring with all of these easy tactile tests. The knuckle method will yield more accurate results than just examining the surface appearance. Whenever my finger comes out sponge-like clean with just a bit of dampness, it's a sweet spot. Supposedly, adding cinnamon powder to the soil inhibits the growth of some fungi (it's supposedly antifungal).
Immediately respond to any early signs of mold by isolating and treating the source of the issue. Separate the affected trays immediately. Two sprays of chamomile tea a day is a natural method until your plant regains health. These methods have saved and revitalized many crops in my urban garden, sort of thing.
Read the full article: How to Grow Microgreens Indoors at Home
