At the latest when you want to grow plants such as wild garlic or peonies from seeds, you will be confronted with the special requirements of cold germs. In this article, we explain what frost and cold germinators are and how you can reliably germinate their seeds.
Definition of cold and frost germs
Cold germs are plants whose seeds need a week-long cold stimulus to sprout. The seeds are initially in a resting phase (dormant). The seed dormancy in cold germs is almost always triggered by a highly concentrated plant hormone (abscisic acid) inside. It prevents the cold-sensitive plants from germinating in autumn and the tender young plants from freezing to death in the subsequent frost period.
The seeds survive the winter months outdoors. During this time, the abscisic acid is gradually degraded. As soon as the temperatures rise again, the level of the plant hormone has fallen so far that the seed sprout.
The term cold germs include frost and cold germs. However, frost germs require significantly lower temperatures for seed dormancy to break through than cool germs, which are adapted to moderate climates.
Which plants are typical cold germs
There are both vegetables and ornamental plants and trees that are among the cold germs:
- wild garlic
- apple tree
- Stone fruit such as cherries, plums, or mirabelle plums
- Christmas rose
- flame flower (phlox)
- forget Me Not
Sow cold germs
There are two ways to get cold germs to germinate reliably:
Sowing in autumn
Sow cold germs in November directly in the bed or in a seed container that you simply leave outside. Mark the spot with a plant label so that you can distinguish the germinating seed from weeds in spring.
During the winter months, you don’t have to worry about the seeds. When temperatures rise in spring, the seeds begin to germinate.
Stratify cold germs in the refrigerator
To break the cold dormancy, you can also store the seeds in the refrigerator for a few weeks. To do this, proceed as follows:
- Fill a freezer bag with two parts potting soil and one part sand.
- Add the seeds and mix thoroughly.
- Moisten the mixture slightly.
- Place the open foil bag in the vegetable compartment of the refrigerator.
- Make sure the mixture doesn’t dry out and shake it up once a week.
- When it gets warmer outside, sow the stratified seeds outdoors.