Cold germs: list & procedure for sowing

Cold and frost germs require weeks of cold stimulation for germination. We introduce the phenomenon as well as some representatives of the cold germs and give tips for sowing.

Not all seeds are ready to germinate again immediately after they have been harvested and dried in autumn. Many of our domestic plants are cold germs or also cold germs. We will introduce you to the phenomenon, explain what it means for the seeds, provide a list of cold or frost germs and give tips on how to get them to germinate after all.

Cold germ: what does that mean?

Frost or cold germs are plants whose seeds cannot or only hardly germinate without a long cold period. The seed is in a seed dormancy, the so-called dormancy. This dormancy can result from a very hard seed coat, a not yet fully developed plant embryo inside or from germ-inhibiting substances in the embryo or nutrient tissue. Unfavorable environmental conditions such as drought also prevent the seeds from germinating. Many seeds are a combination of different types of dormancy that must be overcome before germination can occur.

The cold germs are mainly germ-inhibiting substances inside, which trigger dormancy. A highly concentrated plant hormone, abscisic acid, is usually responsible for this dormant seed. This hormone is supposed to prevent cold-sensitive plants from germinating as early as autumn and from perishing and freezing to death as a result of the winter frosts that follow. Instead, these seeds survive the winter outdoors and don't germinate until spring, when temperatures rise again. The abscisic acid is slowly broken down by the weeks of cold stimulation and the seeds can finally sprout. The exposure to cold either takes place naturally outdoors or it can be artificially simulated in the refrigerator or freezer.

The process of deliberately dissolving the dormancy through artificial cold is also called stratification. In addition to most native tree species, the cold germs also include numerous ornamental and useful plants in our gardens. Your seeds are prepared to wait for the cold winter first and only germinate in the following spring. In mild or tropical warm areas, the seeds of the native species usually germinate directly, there they have no frost or winter to fear and a cold-dependent dormancy makes no sense would.

Note: The term “cold germs” summarizes the frost germs and cooling germs. The former require significantly colder temperatures to break the dormancy than the cooling germinators, which are adapted to milder winters.

List of cold germs

Cold germs are generally at home in the temperate and polar zones, which also includes many plants that are native to us. In the following list we give you an overview of cold germinating useful and ornamental plants.

Which vegetables are cold germs?

When it comes to vegetables, there are very few cold germs, because many of the species that we cherish and care for in the garden come from significantly warmer areas where the seeds do not need any dormancy. These include the almost forgotten Chervil (Chaerophyllum bulbosum) as well as the two perennial vegetable bushes Wild garlic (Allium ursinum) and the one based on the coast Sea kale (Crambe maritima), which only needs mild temperatures above 5 ° C. Salad (Lactuca sativa) is not a cold germ, it is only preferably grown in the cooler months in spring and autumn, as it tends to shoot in summer and then no longer tastes particularly good.

Which types of fruit are cold germs?

Many types of fruit that grow here let their seeds rest in winter. Which includes Hazelnuts (Corylus avellana), Walnuts (Juglans regia), Wild fruit like that Cornelian cherry (Cornus mas) and all rose plants (Rosaceae). Belong to this big family Apples (Malus x domestica) and pears (Pyrus communis), as well as stone fruit - cherries (Prunus avium), Mirabelle plums (Prunus domestica subsp. syriaca), Plums (Prunus domestica) and Co.

Which herbs are cold germs?

Many herbs naturally occurring in our latitudes are also cold germs, for example chives (Allium schoenoprasum), dill (Anethum graveolens) as sage (Salvia officinalis), Woodruff (Galium odoratum) and arnica (Arnica montana).

Which flowers are cold germs?

Some domestic annual flowers that reproduce by seeds also belong to the species with a cold-dependent seed dormancy. Typical cold germs are poppy seeds (Papaver), Cornflowers (Centaurea cyanus), some species of light carnation (Silene) and violets (viola). Even Snapdragons (Antirrhinum), some mullein (Verbascum), the pretty corn wheel (Agrostemma pallida), the annual silver leaf (Lunaria annua) as well as some herons' beaks (Erodium) and some milkweed plants (Euphorbia) are among the cold germs.

Which perennials are cold germs?

Many of our native perennials are cold germs because they have adapted in their development to the cold winters in our latitudes. Exotic perennials from warmer areas, on the other hand, often lack dormancy. Cold-germinating perennials include, for example, Adonis (Adonis), Christmas roses (Helleborus niger), Flame flowers (phlox), Peonies (Paeonia), Cowslips (Primula veris), forget Me Not (Myosotis) and also the lavender (Lavandula angustifolia) is a cold germ.

List of cold germs at a glance:

• vegetables: Chervil, wild garlic, sea cabbage
• fruit: Hazelnuts, walnuts, Cornelian cherries, rose plants, stone fruits
• Herbs: Chives, dill, sage, woodruff, arnica
• flower: Poppies, cornflowers, some species of light carnations, violets, snapdragons, mullein, corn wheel, silver leaf, some heron's beaks, some milkweed plants
• Perennials: Adonis, Christmas rose, flame flower, peony, cowslip, forget-me-not, lavender

Sowing cold germs: this is how you proceed

There are two ways to successfully germinate cold germinated seeds. With little effort, you can simply sow the frost germinator outside in late autumn from October to November in the bed or in a sowing container that you leave outside for the winter. When sowing the cold germs, note the respective planting depth of the seeds and mark the place with a label so that you will know later what will come up here in spring. Now you can leave the seeds alone in winter, because they are still in dormancy and do not require any additional care. As of March, the seeds begin to germinate as the soil temperatures rise. Depending on the species, it can take until mid-April before you see the first little plants. Cold germs can also be sown outdoors in summer. However, they do not germinate until the following spring.

tip: Some seed dealers of dormancy seeds sell seeds that have already broken dormancy. You are only in a waiting state before germination, which is achieved by drying. They have a limited shelf life, but germinate immediately when they are sown. The processes for achieving this status are usually patented and have special additions to their names.

How do you sow cold germs outdoors?

• Sow in late autumn from October to November in the bed or in a sowing vessel that is outside.
• It is best to mark the location of the sowing so that you can still find it in the spring.
• Germination begins between March and mid-April when the temperature rises.
• Some seed traders sell seeds with broken dormancy that no longer require a cold stimulus.

A non-seasonal method is to break the dormancy of the seeds with the help of the refrigerator. Cold germs can be stored here for a few weeks all year round and then germinated. It is important to first let the seeds soak in warm water for one to two weeks. Dry seeds will hardly germinate even after cold treatment. Now mix the seeds with a potting soil, about a third of which has been topped up with sand.

Our Plantura organic herb & seed compost is ideal for this because it is low in nutrients and at the same time has a very loose consistency, which facilitates germination. Moisten the seed-soil mixture well and put it in a freezer bag. Label it with the date so that you can clearly see the weeks that the bag has now been in the refrigerator.

Alternatively, you can also put whole seed trays in the refrigerator. Here, however, it is important to ensure that the substrate never dries out. A cling film can easily help. Depending on the type of plant, the duration and optimal temperature for lifting the dormancy are different. In general, seeds from cold germs require temperatures between -4 and 4 ° C and three to twelve weeks of stratification. However, some trees need a few months of cold weather. After sufficient time in the refrigerator, set up the seed trays at a mild temperature of 5 to 12 ° C. The earthGSimply layer emic from the freezer bag flat in a cultivation vessel. At the slightly higher temperatures, the seeds now begin to germinate. After a few weeks, be piqued and implemented as usual.

How do you sow cold germs in the refrigerator?

• The dormancy of the seeds can also be broken in the refrigerator.
• For this purpose, the seeds are stored in the refrigerator for a few weeks in a freezer bag filled with potting soil and sand in a ratio of 2: 1.
• Alternatively, whole seed trays can be placed in the refrigerator, but the substrate must not dry out.
• Depending on the type of plant, different temperatures and lengths of the cold period are necessary for germination.
• If enough time has passed, the seeds are sown in cultivation containers or the finished seed trays are placed in a suitable location.
• A bright place at 5 - 12 ° C is ideal for germination.

Whether cold germs or not, we must first of all of all plants Gaining seeds and dry them well and store them until the next sowing. We give tips on individual species and how you can get good seeds from them.