✍️ Sonia Pardasani, Founder BageechaBox | 🕐 7 min read | Troubleshooting Guide
Quick answer: Mold on microgreens is almost always caused by too much water, poor airflow, or seeds sown too densely. Prevent it with bottom watering only, correct cocopeat moisture, constant airflow, proper seed spacing, and clean trays between batches. If mold appears on a tray you intend to eat, don't try to treat and salvage it — discard the tray and start fresh with clean, sanitised equipment.
How to Prevent Mold on Microgreens
Mold is the most common problem in microgreens growing — and it's almost always caused by one of three things: too much water, no airflow, or seeds sown too densely. Here's how to prevent and fix it.
Prevention — The 5 Golden Rules
- Bottom water only — never mist the canopy after germination. Wet leaves = mould.
- Correct cocopeat moisture — moist, never soggy. Press test: water should not drip.
- Airflow at all times — keep a window open or a fan circulating near the tray.
- Don't overcrowd seeds — seeds should be close but never overlapping.
- Clean trays between batches — wash with soap, dry fully before reuse.
Root Hair vs Mold — How to Tell
Root hair (normal): Fine white threads close to the stem base only. Uniform pattern. No smell. Does NOT spread upward.
Mold (problem): Cottony fluffy patches spreading upward and across the surface. Musty or sour smell. Spreads visibly over 24–48 hours.
If Mold Appears — What to Do
- Confirm it's mold and not harmless root hair — see the comparison above.
- If confirmed, discard the whole tray, including the growing medium. Don't try to treat mold on food you plan to eat with home remedies — surface treatments don't reliably eliminate contamination below the visible patch.
- Don't reuse the discarded cocopeat in a future batch.
- Before your next sowing, fix the underlying cause — usually overwatering, poor airflow, or seeds sown too densely (see the Prevention section above) — and start with a clean, sanitised tray.
Monsoon Extra Care
July–September is the hardest season. Humidity above 70% means mold spores are everywhere. Harvest 1–2 days earlier, keep fans running continuously, and stick to fast-growing varieties like Radish and Mustard.
Frequently Asked Questions
What causes mold on microgreens?
Almost always one of three things: too much water (especially top watering that wets the canopy), poor airflow that lets spore concentration build, or seeds sown too densely so air can't reach the medium surface.
How can I tell root hair from mold?
Root hair is fine, uniform white threads close to the stem base only, with no smell, and it doesn't spread upward. Mold is cottony fluffy patches that spread upward and across the surface, usually with a musty or sour smell, visibly spreading over 24–48 hours.
What should I do if mold appears on my microgreens?
If you see mold (not harmless root hair — see above) on a tray you intend to eat, discard the whole tray and the growing medium rather than trying to treat it. Fix the underlying cause — usually overwatering, poor airflow, or dense sowing — before starting your next batch with a clean, sanitised tray.
Is monsoon season harder for preventing mold?
Yes, July–September is the hardest season for mold prevention — humidity above 70% means mold spores are everywhere. During monsoon, harvest 1–2 days earlier than usual, keep fans running continuously, and stick to fast-growing varieties like Radish and Mustard.