Light and dark germs: list & differences

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

If you want to propagate plants from seeds, it is rarely enough to simply put a hand in the seed throwing up a dug bed and hoping that in the summer it will be a lush vegetable or flower garden has grown. Depending on the plant genus or species, there are a few things to pay attention to when sowing, which must be individually adapted for successful propagation. The budding plants need sufficient 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 light 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 is optimally supported. We have also compiled a list of the most important light and dark germinating plants for you.

Light and dark germs: different light conditions

It shouldn't come as a surprise to many that mature plants react to different light conditions. But even as seeds, 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-wavelength, high-energy light is blue, while long-wavelength, low-energy light appears dark red. The light spectrum is registered in the plant and in the seed by proteins, so-called photoreceptors. The resulting changes that occur in the seed are called photomorphogenesis. This process is the prerequisite for germination for all seeds.

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: bright red (HR with 660 nm) and dark red (DR with 730 nm). Exposure to HR results in conversion of the phytochrome to the active DR form. If you now expose with DR, the active DR phytochrome is converted back 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 crucial role, which is the external light conditions reflect.
Blue light is registered by cryptochromes, which can also contribute to or inhibit germination. Germination is directly activated by transcription factors of genes through light information transmission.

All plants need light to germinate. However, different plant species need different light intensities or 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 seed types and claims

Light germinators 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. Accordingly, 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 if they lie underground in the dark. For this reason, seeds of light germinators are sown on earth. Light sprouters, like some lettuce varieties, sprout at high HR: DR ratios.

The whole thing is different with dark germs: the seeds are usually large and thick. Accordingly, they are bulging with reserve substances for a strong budding. A layer of soil on them is not a problem. On the contrary, the layer of earth filters or dims the light. This is necessary to start the germination process in the seeds of dark germs. The seeds are therefore pressed into the ground 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).

Sowing and requirements of light germs

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

• Clean seed pot with a high-quality potting soil such as the Plantura Organic Herb & Seed Soil to fill
• Flood potting soil
• Drain excess water
• Sow the seeds about 2 cm apart on the soil, only pressing lightly to make contact with the soil
• Apply a thin layer of sand to minimize risk of mold (maximum as thick as the seed itself)
• Cover the culture vessel with a foil hood to increase the humidity
• Always keep the substrate moist but not wet (use a water atomizer so that the seeds are not washed away)
• Bright location, but no direct sun
• From germination, remove the foil hood once a day for airing and acclimatization
• Transplant into small pots as soon as the second pair of leaves appear
• Cover pots with foil hood

The crucial 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 significantly. There are plant species where the first seeds germinate after just a few days and others where you have to wait several weeks for the first seedling.

As an alternative to the seed bowl, you can also moisten a handkerchief with water. The handkerchief is spread out and the seeds are spread on it. The cloth is then folded closed so that a single layer of damp handkerchief is underneath and on top of the seeds. The whole thing is placed in a transparent container or bag and left in a bright place at the right temperature until the seeds germinate.

Sowing and claims of dark germs

Depending on the plant species, you also have to set certain parameters individually for dark germs, but in principle the sowing of dark germs works as follows:

• Clean seed tray with potting soil - for example our Plantura Organic herbal & seed soil - to fill
• Water the potting soil from below until the soil is well saturated; drain excess water
• sow seeds
• Sow seeds at least twice as deep in soil as the seeds are tall; 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 spray or water carefully
• From germination, remove the foil hood once a day for airing and acclimatization
• Transplant into small pots from the second pair of leaves
• Cover pot with foil hood

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

List of dark and light germs

Although one can distinguish between dark germinators and light germinators based on the size of the seed alone, a list gives you a feeling of security. We have therefore put together an overview of dark and light germinating plant species for you.

Examples of light germs

Light germinators include plants such as:

• Medicinal Valerian (Valeriana officinalis)
• oyster plant (Mertensia maritima)
• basil (Ocimum basilicum)
• Savory (Satureja)
• blackberry (Rubus sectio Rubus)
• curry herb (Helichrysum italicum)
• dill (Anethum graveolens)
• Real chamomile (Matricaria chamomilla L.)
• Real coriander (Coriandrum sativum)
• real lavender (Lavandula angustifolia)
• Real thyme (Thymus vulgaris)
• elephant foot (Beaucarnea recurvata)
• strawberry (Fragaria)
• tarragon (Artemisia dracunculus)
• Red Foxglove (Digitalis purpurea)
• garden cress (Lepidium sativum)
• geranium (pelargonium)
• bluebell (campanula)
• raspberry (Rubus idaeus)
• Horned Violet (Violoa cornuta)
• carrot (Daucus carota subsp. sativus)
• catnip (Nepeta cataria)
• lettuce (Lactuca sativa)
• Caraway seed (Carum carvi)

• snapdragons (antirrhinum)
• lily of the valley (Convallaria majalis)
• marjoram (Origanum majorana)
• evening primrose (Oenothera)
• carnation (dianthus)
• oregano (Origanum vulgare)
• pampas grass (Cortaderia)
• petunia (petunia)
• peppermint (Mentha × piperita)
• primroses (Primula)
• rye (Secale cereale)
• rosemary (Rosmarinus officinalis)
• sage (Salvia)
• celery (Apium)
• Mustard (Sinapis)
• Tomatoes (Solanum lycopersicum)
• venus flytrap (Dionaea muscipula)
• Forget Me Not (myosotis)
• Virginia tobacco (Nicotiana tabacum)
• lemon balm (Melissa officinalis)
• lemon verbena (Lippia citriodora)

Examples of dark germs

Most types of vegetables belong to the group of dark germs, but also other plants such as:

• aubergine (Solanum melongena)
• borage (Borago officinalis)
• Christmas rose (Helleborus niger)
• aconite (aconite)
• Lamb's lettuce (Valerianella)
• fuchsia (fuchsia)
• cucumber (Cucumis sativus)
• pumpkin (Cucurbita)

• lovage (Levisticum officinale)
• lily (Lilium)
• lupine (lupinus)
• Corn (Zea mays)
• parsley (Petroselinum crispum)
• Larkspur (delphinium)
• snowdrop (Galanthus)
• chives (Allium schoenoprasum)
• sunflower (Helianthus)
• pansies (Viola tricolor)
• hollyhock (Alcea)
• lemongrass (Cymbopogon citratus)
• zucchini (Cucurbita pepo subsp. pepo convar. giromontiina)

You don't know exactly when which plants should best be sown? Our sowing calendararticle can surely help you!