We wrote this article to help give you confidence and to help set an expectation that you can successfully germinate and grow any seed of your choice. Learning how to grow seeds can be frustrating if you do not fully understand what is taking place when a seed germinates. It can be a breath-taking, a spiritual experience, if you could just watch nature and pay attention to what is actually taking place. Some of the most beautiful time-lapse footage is that of a seed sprouting and watching it grow.
Wikipedia explains stratification as in horticulture, stratification is a process of treating seeds to simulate natural conditions that the seeds must experience before germination can occur. Many seed species have an embryonic dormancy phase, and generally will not sprout until this dormancy is broken.
During our many years of growing seeds now which is now over 20 years, we have found this very useful in our plant production. This “cold-stratification” process. Especially, for seed germination. Seeds can be costly for different varieties and cultivars of plants and fully knowing how to grow seeds can help you get the germination results you want and expect.
So let’s see if we can explain cold stratification in a way that will help you in growing your next batch of seeds.
Many people think that when they get seeds that they will just automatically grow when the plant them in the ground. At that point you have set your self up to be disappointed very quickly. Don’t stop at the planting directions for growing your plant seeds. If they don’t work do not blame the instructions anymore. Go beyond someone else’s instructions and become a seed expert with this one little tip.
What is Cold Stratification of Seeds?
Tip 1 – Dry Seeds
Collect your seeds. Dry out your seeds. If you have received seeds from someone else make sure they are dry and not wet or damp. The water in the seeds will promote fungus and rotting of the seeds prior to the cold stratification process. This will make them not viable which means they will not grow and have been corrupted. Once your seeds are fully dry you are ready to move on to step two. Normally a seed will dry out within 48 hours.
Tip 2 – Cold Stratification (Prep)
Place the dried seeds inside a zip lock bag. Seal the bag tight because it will prevent any additional moisture getting in. You want an air tight package so that the seed stays viable and ready to grow when the time is right.
Tip 3 – Cold Stratification (The Process)
Your refrigerator is an ideal place to store your seeds while they go through the cold stratification process. Cold stratification is actually mimicking nature during its cold season.
When you purchased your seeds and then you received them but they did not go through this process, how will you know? You don’t know. Unless the company that sold you the seeds tells you they put your seeds through cold stratification, you will not know. So just assume that every seed package you get from now on did not go through this process.
Tip 4 – Cold Stratification (How Long Does It Take?)
You will want to keep your seeds inside the refrigerator or in storage at just above freezing (ideally your vegetable crisper) for a period of 3-4 weeks. This is the “sweet spot” the best length of time that we have come up with. Longer periods doesn’t improve the germination percentage or rate any more by adding time in the cold. Shorter periods however, will weaken and affect germination in a negative way.
Once your seeds have completed the cold stratification process, they are now ready to plant. Your seeds can stay in cold storage for as long as you want. This is in fact what seed banks do across the world. Seeds stay viable for hundreds of years this way. So if you have seeds ordered in winter, keep them in the fridge until spring. Once again, just make sure they are dried before doing this.
Additional “Pro Tip” about Cold Stratification of Seeds
We have used this method on our seeds and maintain and germination rate between 97-100% with viable seeds. One way to tell if a seed is viable do a “pinch test” if it feels like an full seed then the embryo is probably in tact.
Also, use this cold stratification method on your tropical seeds. Even tropical seeds enjoy a period of time in the cold. They come out more aggressive afterwards.
The 3 things a seed needs to grow. Sunlight (Warmth), Water and Earth (Soil) Check out our Grow Lights section if you are growing your seeds in the winter at home.
Now you are ready to add those three elements and watch your seeds thrive!