Some like it hot. But some don't.
There are seeds that prefer the brisk cold air, desiring temperatures between -4 and 4°C in order to germinate. These cold-weather seeds are best sown in autumn or winter if you want to grow them in your garden or pot the following year. Such seeds include wild garlic, meadowsweet, lady's mantle, cyclamen, violets, bluebells, Christmas roses, cowslips, lavender and many more.
It's kind of crazy: instead of warmth, "cold seeds" actually need the cold weather to germinate. So don't try and sow these seeds in the spring or summer. Best wait for autumn and winter, and let nature work for you!
And here's a little trick: in your refrigerator you can fool the seeds into thinking it is winter, making them sprout in spring. This method might be a bit hit-or-miss, as plant seeds, for example, need cold periods or temperatures of different lengths or preceding warm phases. But you can still give it a shot – after all, gardening is most fun when we bring a spirit of experimentation, curiosity and optimism!
Here's a general rule for cold seeds: a plant flowers, forms seeds and usually lets them fall to the ground in early autumn. There the seeds lie about at mild temperatures as they get acclimated to the cooler weather in late autumn. Finally, winter comes and gives the seeds the cold-rush they need. Like the cold air outside on a winter morning, the cold wakes them up, breaking the hibernation and dormancy.
This is caused by growth-inhibiting substances in the seeds. Its purpose is to prevent the seeds from sprouting directly after being sown naturally in early autumn, and the frost-sensitive young plants from freezing to death in winter. The cold stimulus ensures a slow, gradual breakdown of the growth-inhibiting substances. The seeds then sprout in spring, sometimes not even until early summer, when the temperatures are just right. Just like Goldilocks.
If you want to sow cold germs yourself, there are different approaches:
For autumn / winter sowing in your bed: sow the seeds in a predetermined location. Then water them. Nature does the rest! The natural climate uses cooler temperatures to determine when the seeds germinate. If it does snow, don't worry! A layer of snow on the already-sown seeds is kind of like a blanket – definitely advantageous, as it keeps the temperature (optimally between -4 and 4 ° C) and humidity stable. Plants dig that.
For autumn / winter sowing on your balcony: just like you after a long day in the office, let the seeds soak in a warm water bath. Smooth jazz playlist and glass of red wine optional. The next day, take the seeds out and distribute them in the pots / window boxes with potting soil at the intended distance, sifting over with some fine soil according to the type of seed (light germinator / dark germinator). Then water them. Place in a sheltered place, preferably in a partially shaded location. Place grids or rabbit wire over them to protect them from hungry birds who might be feeling peckish. Always keep them slightly moist for the next few months until they germinate.
For autumn / winter sowing in a seed tray:
Here's what you need:
Flat piece of wood to press seeds
Spray bottle / shower ball
If necessary, a sieve
Wire or fleece
Let your seeds soak in a warm water bath overnight.
Fill your seed tray with potting soil, up to about 1 cm below the edge.
Lightly press the soil.
Sow the seeds in rows so you can see them better after they germinate.
Carefully press the seeds down with a flat piece of wood. Do not use too much force; in fact, the soil should remain loose so that it can absorb water and oxygen.
If you have sown dark germs, you have to sift a thin layer of soil over it.
Moisten with a spray bottle or shower ball.
Cover with fleece or mesh for protection against birds.
Put it outside in a sheltered place.
Keep it moist.
4. For sowing in spring using a refrigerator: if the winter is too mild and does not have enough of a cold period, or if you simply prefer to sow in spring, you can put the seeds in the refrigerator for a few weeks. Your refrigerator must have a temperature between 0 and 5°C (the temperature in the brackets on the inside of the refrigerator door is usually only 8°C). You can also put your seeds in a warm water bath overnight. Then put them in a seed tray with potting soil or on a mixture of potting soil and sand. Gently press it down with a piece of wood. You may still want to sift a thin layer of soil over it, depending on whether your seeds are light germs (these don't require an extra layer of soil) or dark germs. Once you've sown the seeds, moisten the whole thing with a spray bottle or a shower ball. With this refrigerator method, of course, you don't need a grid. Instead, you should put a foil over the seed tray to slow moisture loss. Even with this method, you have to make sure that your seeds don't dry out.
Note 1: If you don't have space for a seed tray in your refrigerator, or if you simply don't want to grow the plants in trays, you can put the seeds in a sealable container with some sand and soil and put that in the refrigerator.
Note 2: The freezer compartment is not suitable for breaking the hibernation phase, as the seeds will get way too cold too quickly.
After a few weeks of refrigeration, remove the seed tray and place it in a bright place with a temperature between 5 and 12°C. The seeds will slowly get used to the warmth again and receive that long-awaited message-in-a-bottle: “springtime – time to!”. Still, a little patience is required. Depending on the seed, it can take several weeks, sometimes even months, before you see the first spot of green.
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