Light germinators and dark germinators and how to grow them correctly
Plants are known to be classified and sorted according to many characteristics. One of these identifying characteristics is whether the plant is a dark germinator or a light germinator. It sounds complex and scientific, but it's not. In fact, the terms actually mean exactly what they express: Do plant seeds need light to germinate? Or is light detrimental to proper growth?
What makes light germinators sprout
Light-germinating plants won't germinate if the seeds receive sufficient warmth, oxygen, and moisture—but no light. Whether it's purple loosestrife, forget-me-nots, Virginia tobacco, or prominent crops like celery, lettuce , carrots , thyme , basil , and other culinary herbs, all of these plants won't sprout if their seeds don't receive light. The photoreceptors of phytochromes, proteins that respond to light stimuli, are responsible for this. The process that causes seedlings to sprout is called photomorphogenesis, and we could explain it in detail here, but that would probably be rather boring. If you'd like to know more, look it up in the encyclopedia of biology :) 
Daisies are light germinators. Therefore, the seeds in these seed bombs are placed on the outside.
It's more interesting to shed light on (in the truest sense of the word) how light-germinating plants are made to grow in gardening terms, i.e., in practice. This is how it works: First, the seedlings must be gently pressed down to make contact with the soil. However, the layer of soil covering the seeds must not be thicker than a single plant seed, because light must penetrate. And the soil needs moisture, which is best preserved with transparent film. If the seedlings are then irradiated with infrared or red light, their germination capacity increases dramatically. In keeping with Goethe's last words: more light! But please, the right kind.
Dark germinators like it dim, but still need light waves
The opposite of light is dark, and this already suffices to describe what dark-germinating plants need: a generous layer of soil to prevent direct light from penetrating the seeds. Light inhibits the growth of these seeds , at least short-wave, bright light. However, dark-germinating plants cannot survive entirely without light waves: biologists suspect that long-wave light can penetrate the soil layers and also trigger photomorphogenesis in the plant seeds. Nevertheless, a darkened room is ideal for growing dark-germinating plants.
But which plants are dark germinators? There are some edible ones here too, such as sweetcorn , coriander , nasturtiums, cucumbers, chicory, pumpkins and lamb's lettuce. Most vegetables are dark germinators - and they can be germinated relatively easily on a plate. Simply place a folded tissue that has been sprayed with water on the plate, then scatter the seeds on it, then cover this with a second damp tissue and finally store the whole thing in a sealed plastic bag until the seedlings sprout. Okay, you can't grow a three-meter-long stalk of corn this way, but lamb's lettuce and nasturtiums will thrive this way in your own kitchen.
The rule of thumb
If you're not entirely sure whether a plant is a light or dark germinator (and can't or don't want to Google it right now), you can follow a rule of thumb. It states that very small and light seeds are light germinators because the energy contained in the seed isn't enough to allow the seed to grow to the light. Dark germinators, on the other hand, have large seeds with a lot of stored energy, allowing these seeds to fight their way through the soil to the surface.
