The blackout stage is one of the most misunderstood parts of microgreens growing — and getting it wrong is the single biggest cause of leggy, yellow crops. Here's exactly what it is, why it matters, and how to time it correctly in India.
What Is the Blackout Stage?
After sowing, you cover your tray with another tray to block all light. This does two things: the darkness triggers the seedling to push upward aggressively seeking light, and the weight of the cover pushes roots down into the cocopeat. Together, these produce strong, upright stems.
How Long to Keep in Blackout
| Season | Duration |
| Summer (25–40°C) | 36–48 hours — check at 36h |
| Winter (15–25°C) | 48–60 hours — check at 48h |
| Monsoon (high humidity) | 36 hours maximum — humidity risk |
How to Know When to Remove the Cover
Check at the earliest time. Lift the cover: if shoots are 1–2cm tall and pushing against the lid, move to light immediately. If shoots are only just sprouting (under 0.5cm), cover for another 12 hours and check again.
What Happens If You Leave It Too Long?
Shoots stretch desperately seeking light and become leggy — long, thin, and weak. They often fall over. This is one of the most common beginner mistakes. If this happens, move to light immediately — the crop is still edible but won't fully recover.
Questions about blackout timing? Ask Sonia 🌱