How do I troubleshoot common microgreen problems?

White fuzz at the base of microgreen stems is almost always root hairs, not mold. Root hairs are a normal, healthy sign of vigorous growth. Actual mold looks and behaves differently.

Mold is the most common microgreen problem, caused by high humidity, poor airflow, and overwatering. Prevention is far easier than treatment, but caught early, mold can be managed without losing the tray.

Yellow microgreens can have several causes, but the two most common are too little light and overwatering. The fix depends on when the yellowing appears.

Damping-off is a fungal disease where seedlings suddenly collapse at the soil line, with stems turning brown and mushy. It spreads fast and can wipe out an entire tray overnight. Prevention is essential because there's no cure once it starts.

Seed hulls (shells) stuck on top of microgreen leaves are a cosmetic nuisance that can also block light and slow growth. This is most common with sunflower, beet, and cilantro microgreens.

Tall, spindly microgreens with thin stems that fall over are etiolated — stretching toward insufficient light. This is purely a lighting problem and is easy to fix.

Patchy trays with bare spots and uneven growth are usually caused by dry seeds, uneven sowing, or inconsistent moisture during the critical first 24-48 hours. Pre-soaking larger seeds solves most germination problems.