Few things test a gardener's patience like an empty tray, days past the "expected germination" window printed on the packet. Before you assume the seeds were bad, work through these five causes — in order of how often they're actually the problem.
1. Inconsistent Moisture
Germination is a chemical process that, once started, cannot be paused. If the soil dries out even once during germination, the emerging root can die and the seed won't get a second chance. The fix is consistency, not quantity: keep the medium evenly moist, like a wrung-out sponge, and check daily. Covering trays with a clear lid or plastic wrap until sprouting helps hold moisture without you having to water constantly.
2. Wrong Temperature
Every species has a germination temperature range, and it's usually narrower than people expect. Cool-season crops like spinach and lettuce can actually refuse to germinate if it's too warm, while tomato, chilli, and cucumber stall out in cold soil. If your trays sit on a cold floor or a draughty windowsill, germination can take two to three times longer than expected — or fail outright. A seedling heat mat or simply moving trays to a warmer spot solves this in most homes.
3. Sowing Too Deep (or Too Shallow)
Depth matters more than most people realise. Fine seeds like lettuce, petunia, and many herbs need light to germinate and should sit on the surface or under only a light dusting of mix — bury them and they'll never sprout. Larger seeds like beans and pumpkin need to be pushed down further, around 2-3 times their width, or they'll dry out before rooting. When in doubt, the seed packet's depth guidance is precise for a reason — follow it.
4. Old or Poorly Stored Seed
Seed viability drops over time, and heat and humidity accelerate the decline. Seeds stored in a hot shed or a damp kitchen drawer lose viability far faster than the same seeds kept cool and dry. If you're using seed that's more than a year or two old, or unsure how it was stored, do a quick germination test: place 10 seeds on a damp paper towel, fold it, seal it in a bag, and check after the expected germination period. If fewer than 6-7 sprout, sow more thickly than usual to compensate.
5. Damping-Off and Soil-Borne Fungus
If seedlings do emerge but then collapse at the soil line within days, that's damping-off — a fungal issue caused by overly wet, poorly ventilated conditions, often in reused pots or garden soil rather than a sterile seed-starting mix. Prevention is far easier than cure: use fresh seed-starting mix, avoid overwatering, ensure airflow once seedlings emerge, and never reuse trays without cleaning them first.
When to Just Re-Sow
If you've ruled out the above and nothing's come up by roughly double the expected germination time, it's usually faster to re-sow with fresh seed than to keep waiting. Gardening rewards troubleshooting, but it also rewards knowing when to start again.
