One of the interesting little bits of lore about germinating seeds I’ve picked up over the years is that most annual and vegetable seeds (perennials too come to think of it) germinate quite nicely without being buried or restricting light.
While some (pansies come to mind) absolutely require darkness, most others don’t.
What they need however is a slight seed covering that helps them orient themselves and keeps a steady moisture level around the germinating seed. We’re not talking a lot of moisture here – but “just damp”.
The Best Coverings For Seed
The absolute best germinating covering is soilless mix. It allows light through to induce germination in most seeds while keeping the soil moisture correct. ( Do not use anything on impatiens – “maybe” a very light covering of vermiculite as they do require light to germinate.)
Put 1/8 inch of soilless mix. on top of seeds for the vast majority of germination needs.
You’ll know you need a covering when you see seeds germinate and the radicles (first long root) curl around on top of the soil or the seed stems are really long in the seedling tray.
I generally use an old aquarium covered with a clear plastic household wrapping for seed germination (the clear plastic wrap almost completely eliminates the need to water once the soil in the germinating pot is thoroughly wet before sowing)
An old trouble light with a 100 watt bulb keeps the temperature warm enough.
And the day I see seeds start to germinate in the pot is the day I take it out of the aquarium and put it on a growing shelf (higher light).
I do not allow seeds to grow in the aquarium as there will be far too much moisture and heat for great growth.
But the trick is in the covering. Just enough to give the seed a sense of up-down and to retain a moisture level around the seed. But not too much so the seed is “buried” and dark.