Light and dark germs: list & differences

One hears again and again of dark and light germs. We reveal exactly what the difference is and which plant belongs to which group.

Seedlings in the sunlight — Germination works under the right lighting conditions [Photo: lovelyday12 / Shutterstock.com]

If you want to propagate plants from seeds, it is seldom enough to simply put a hand with the seed in it Throwing up a dug up bed and hoping that in summer there will be a wonderful vegetable or flower garden has grown. Depending on the plant genus or species, there are a few things to watch out for when sowing, which must be individually adapted for successful propagation. The budding plants need enough water, oxygen, warmth and even now enough sunlight. Depending on the plant, there are differences in germination temperature and duration as well as in the lighting conditions required for germination. Depending on the required light intensity and light spectrum, the plants are then divided into two groups.

We explain the difference between dark and light germs and what you have to consider when sowing so that the respective germination capacity is optimally supported. We have also put together a list of the most important light and dark germinating plants for you.

contents

Light and dark germs: different lighting conditions
Different types of seeds and demands
- Sowing and claims of light germs
- Sowing and demands of dark germs
List of dark and light germs
- Examples of light germs
- Examples of dark germs

Light and dark germs: different lighting conditions

It should come as no surprise to many that mature plants react to different lighting conditions. But even as seeds, the plants perceive light and its different intensities. The intensity or the energy contained in the light depends on the wavelength of the light - the light spectrum. Short-wave, high-energy light is blue, while long-wave, low-energy light appears dark red. The light spectrum is registered in the plant and in the seeds by proteins, so-called photoreceptors. The resulting changes that occur in the seed are called photomorphogenesis. This process is the prerequisite for germination of all seeds.

Seedling with hand and water — All plants need water, oxygen and light to germinate [Photo: Pasuwan / Shutterstock.com]

Plants and their seeds react to changes in light with the help of so-called phytochrome receptors. These sensor pigments primarily register the incidence of red light: light red (HR with 660 nm) and dark red (DR with 730 nm). Exposure to HR leads to a conversion of the phytochrome to the active DR form. If one is now exposed to DR, the active DR phytochrome in turn converts into the inactive HR form. In the dark, the DR phytochrome falls back to the HR phytochrome. The essential factor here is the ratio of phytochromes. In germination and many other processes, such as flower induction, the ratio of active to inactive phytochrome play a decisive role in the external light conditions reflect.
Blue light is registered by cryptochromes, which can also contribute to or inhibit germination. The germination directly is activated by transcription factors of genes through the transmission of light information.

So all plants need light to germinate. However, different types of plants need different light intensities or light spectra, which serve as the starting signal for germination. Depending on the light spectrum required, plants are divided into two groups of germination types: dark germs and light germs.

Different types of seeds and demands

Light germs need light with a high intensity in the range of blue light or bright red light for germination. The seeds are usually very small and therefore contain little storage material, which the seedling uses as an energy source during germination. If it does not receive enough light, the small plant would not be strong enough to fight its way through a layer of soil when it germinates. The seeds therefore do not even begin to germinate when they lie underground in the dark. For this reason, seeds of light germs are sown on earth. Light germs, like some types of lettuce, germinate at a high HR: DR ratio.

The whole thing looks different with dark germs: The seeds are usually large and thick. Accordingly, they are bulging with reserve substances for a powerful budding. A layer of earth on them is not a problem. On the contrary, the layer of earth filters or dims the light. This is necessary so that the germination process is started in the seeds of dark germs. The seeds are therefore pressed into the soil during sowing, but only so deep that enough short-wave light can still reach the seeds. Dark germs like cucumbers (Cucumis sativus) germinate at a low HR: DR ratio (<0.02).

Seedlings in soil — Depending on how much storage material there is in the seed, the seedling can make it through an additional layer of soil or not [Photo: Bogdan Wankowicz / Shutterstock.com]

Sowing and claims of light germs

The basic process of sowing light germs is the same for all types of plants and works as follows:

Clean cultivation vessel with a high-quality cultivation soil such as the Plantura organic herb & seed compost to fill
Flood the potting soil
Drain excess water
Sow seeds at a distance of about 2 cm on the ground, just press lightly to make contact with the ground
Apply a thin layer of sand to minimize the risk of mold (no more than as thick as the seed itself)
Cover the cultivation vessel with a foil hood to increase the humidity
Always keep the substrate moist, but not wet (use a water atomizer, as the seeds are not washed away this way)
Bright location, but no direct sun
After germination, remove the foil cover once a day for ventilation and acclimatization
Prick out into small pots when the second pair of leaves is formed
Cover pots with a foil hood

The most important thing when sowing light germs is that the seeds get enough light in the short-wave range. Individual attention must then be paid to the germination temperature and the time of sowing. The germination time can also differ considerably. There are plant species in which the first seeds germinate after a few days and others in which you have to wait several weeks for the first seedling.

As an alternative to the seed tray, you can also moisten a handkerchief with water. The handkerchief is spread out and the seeds are distributed on it. Then the cloth is closed so that there is a single layer of moist handkerchief under and on top of the seeds. The whole thing is put in a clear container or bag and stored at the right temperature in a light place until the seeds germinate.

Sowing and demands of dark germs

With the dark germs, too - depending on the type of plant - certain parameters have to be set individually, but in principle the sowing of dark germs proceeds as follows:

Clean seed tray with potting soil - for example our Plantura Organic herb & sowing soil - to fill
Water the potting soil from below until the soil is well soaked; Drain excess water
Sow seeds
Put seeds in soil at least twice as deep as the seeds are large; alternatively cover the seed tray with cardboard
Cover the seed tray with a foil hood or something similar
Shady location
Moisten the soil with a water sprayer or pour it carefully
After germination, remove the foil cover once a day for ventilation and acclimatization
Prick out into small pots from the second pair of leaves
Cover the potty with a foil hood

Sowing dark germs — After sowing, the seeds of the dark germs are covered with a layer of soil [Photo: amenic181 / Shutterstock.com]

Here, too, as described for the light germs, the handkerchief variant can be used as an alternative to the seed tray. The damp handkerchief can also be a little thicker. After that, the wrapped handkerchief package is placed in a shady place until the seeds germinate.

List of dark and light germs

It is true that you can distinguish between dark germs and light germs just by looking at the size of the seed, but a list gives you a sense of security. We have therefore put together an overview of dark and light germinating plant species for you.