Why Are My Microgreens Not Germinating?

Opening your tray on day 3 and finding bare, damp medium where sprouts should be is one of the most frustrating experiences in microgreens growing. It wastes time, seeds and effort — and if you do not understand why it happened you are likely to repeat the same mistake on the next tray. Germination failure in microgreens is almost always caused by one of a small number of identifiable and correctable factors.

Old or Treated Seeds

Seed viability degrades over time. Old seed stored in warm or humid conditions loses germination rate faster than seed stored cool and dry. A packet labelled "germination rate 85%" from two years ago may now be at 50% or lower. Treated seeds — coated with fungicide for outdoor planting — often have much lower germination rates in the dense, moist conditions of a microgreens tray, and the coating can inhibit the early root development that makes microgreens germinate so quickly. Always buy from a reputable microgreens seed supplier and check the packet date. If the seeds are over 2 years old, test a small batch before committing a full tray.

Temperature Too Low

Most microgreens seeds need a minimum temperature of 15 to 18°C to germinate, and they germinate fastest at 20 to 22°C. A cold kitchen (below 16°C overnight) can slow or stop germination entirely for temperature-sensitive crops. Basil is the most sensitive, requiring 22°C minimum — it will simply refuse to sprout at cooler temperatures. If your kitchen is cold, use a seedling heat mat under the covered tray during the germination phase. Check the mat temperature with a thermometer and aim for 20 to 22°C at medium level.

Medium Too Dry or Too Wet

Seeds need consistent, even moisture to germinate — neither dry nor waterlogged. A medium that is damp at the surface but dry below will germinate some seeds and not others, producing a patchy tray. A medium that is saturated will create anaerobic (oxygen-free) conditions that prevent germination entirely and encourage fungal rot of the seeds. The medium should feel moist like a wrung-out sponge throughout its depth when you sow. After sowing and misting, the cover should trap enough humidity to keep the medium from drying out for 2 to 3 days. If the medium feels bone dry when you check on day 2, mist again and re-cover.

Seeds Buried Too Deep

Microgreens seeds should sit on the surface of the growing medium, not buried in it. They need oxygen from above to germinate, and the seedling needs only a short distance to push to reach light. If seeds were pressed in deeply or covered with a layer of medium, germination will be slow and patchy. Press seeds gently onto the surface — contact with the medium is all that is needed. Do not cover with extra medium.

Large Seeds Not Pre-Soaked

Sunflower, peas, wheatgrass and corn all have hard seed coats that require soaking in water for 8 to 12 hours before sowing. Without soaking, the seed coat takes several additional days to soften enough for the root tip to emerge — this is not a germination failure but it looks like one on days 2 to 3. If you skipped the soak step for a large-seeded variety, add water to the tray, keep the temperature at 20°C and wait — most will eventually sprout, just later than expected.