How to stratify seeds correctly
If you want to grow bonsai from seeds, you cannot avoid stratification. I will help you to approach this topic successfully.
I find that growing bonsai from seeds has a certain charm. Of course, it takes incredibly long for a seed to become a real tree, but it also offers many advantages.
🌱 One of the most decisive advantages is probably that you have control over the shape of the tree from the very beginning. With nursery plants or Yamadori (trees from the wilderness turned into Bonsai), you always have to make certain concessions and compromises.
In addition, I see this as an opportunity to always sell a few pre-bonsai to get back money for new bonsai projects and of course to gain experience.
Seeds of trees from my area all need stratification to germinate. But why it is like that and how to ensure that stratification is successful, I would like to clarify with you in this article today.
🧐 What is stratification?
This is a process that promotes the germination of various seeds by imitating natural environmental conditions.
In nature, stratification or seed dormancy serves to delay the germination of seeds. This has two central benefits.
The first benefit is that the seeds do not start to germinate directly next to the mother plant. This is particularly useful in relation to trees, as trees need a certain distance from each other in order to grow well.
❄️ The second central reason is related to the seasons. Here in Germany we have cold winters and the seeds are already ripe in autumn. If the seeds were to germinate in autumn, the small plants would have very poor chances of survival in winter.
Therefore, nature has provided a mechanism that does not allow the seeds to germinate until spring arrives.
So during stratification, you simulate the cold period that is needed for the seed to germinate under controlled conditions.
🤔 What happens during stratification?
During the cold phase, the seed changes to improve its germination capacity. Its coat cracks open and water can penetrate the inside.
This triggers some hormonal changes that set the germination process in motion. The humidity during stratification keeps the seed moist and supports essential life processes.
🌸 Which seeds need to be stratified?
In principle, you should stratify all seeds of plants that have their natural origin in temperate climates. These include, for example:
Fruit trees and shrubs: apple, pear, cherry
Nut trees: walnut, chestnut, hazelnut
Ornamental plants and wildflowers: sunflowers, poppy, peony
🪴 How do I best stratify my seeds?
There are two ways to do this. Either you use your refrigerator, then you can stratify all year round or you use nature to do its job.
Let's stick to the refrigerator method today.
🏝️ For this you need a container with sand. It should not be completely closed to prevent mold. The substrate must be wet throughout the entire process. If it dries out, it can damage your seeds.
The sand-seed mixture is shaken once a week and you should check whether it is still moist enough.
Also check whether the seeds are starting to germinate. If this is the case, then the seeds are "ready" and can be sown.
At the moment I am trying a different method. Since my refrigerator is chronically overcrowded, it has to be space-saving.
📱 I saw a time-lapse video on the internet in which stratification was done in a piece of paper towel that was wrapped around the seeds and moistened. Then it goes into a resealable freezer bag and into the refrigerator.
Here you have to be particularly careful to look for mold. Because there is a lot of moisture in the bags and there is no air exchange.
I currently check once a week and renew the paper towels if I suspect that mold is forming.
In fact, I have already brought apple seeds to germinate with this method. The first ones have already moved from the bag to the flowerpot today.
⏰ How long does the process take?
That depends entirely on the seed you want to germinate. I recommend googling again at this point how long it could take in your case.
You also have to be patient. I sowed seeds for pomegranate trees at the beginning of the year and nothing happened in the period in which something should have happened. So at some point I lost interest and was about to throw away the bowl with the seeds.
But when the time came, I discovered green dots on the seeds. So I didn't throw away the bowl and that's why I have thirty pomegranate seedlings today that are waiting to become bonsai.
Nature has its own schedule!
💫 In Conclusion
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Okay, that wasn't a very good summary, so here I try again:
🌡️ Pay attention to the right temperature: The seeds must not be exposed to sub-zero temperatures. A temperature between 2°C and 7°C is fine. So put them in the refrigerator.
💦 Moisture: Your seeds need water to live. Unlike mature plants, they have no way of storing water. So keep them moist at all costs.
💨 Air circulation: Mold is the enemy! So make sure there is enough air circulation and check regularly.
😌 Patience: Give your seeds the time they need. Your bonsai will take 12 years to become a stately little tree anyway. So one more or less month doesn't matter either.
I'd love to hear about your experiences with stratification. What method do you like to use, what experiences have you had, and what might I have forgotten?
I look forward to hearing from you,
Until next time,
Your Sebastian