What is seed stratification?

Have you ever wondered about what the term seed stratification means? Within the circles of horticulture, stratification would be considered as the process of actually pretreating seeds in a similar way that mother nature would. In the process the seed would be subjected to cold as well as moist conditions where the temperature would vary between 34 degree Fahrenheit to 41 degree Fahrenheit (1-5 degrees Celcius).

When controlled, the stratification process is nothing more than ensuring that the seeds in question are subjected to cool, but not freezing conditions for a period that is long enough for the relevant plant species. The time period could be anywhere between one to three months.

Well, in short, it is a term that describes a process. The significant thing about this process is that it is beneficial for the seed because it makes it easier for it to germinate. Which, in turn, makes it possible for it to become a plant, and, eventually, to grow into a vegetable, a tree, a beautiful flower or whatever it is striving for. An example of a plants that needs to be stratified, is Atropa belladonna.

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Atropa belladonna (a perennial plant) does require stratification. Photo by Peganum.

Most gardeners become skilled in the art of stratification by effectively copying the set requirements for a particular seed, but doing so indoors. They do this by placing the seeds in a moistened paper towel that gets put in a sealed container, and in the case of cold stratification, they would place it in refrigerator. For warm stratification, the seeds would just be stored indoors in an environment where the temperature does not exceed 85 degrees Fahrenheit (30 degrees Celcius).

Another way to explain cold stratification. It is the process where one would fool seeds into thinking it is winter, when it is not.

When would cold stratification be needed? Generally, cold stratification are applicable to seeds that need time in the ground during winter time to get them ready for the germination process.

How does it work? In short, the process of seed stratification means that the seed goes from one state to another; it leaves the dormancy and starts to germinate. The seed stratification process may follow different steps depending on what seed we are talking about. For example, it may be a cold process or warm process. Further, the process may occur in your garden or in your home, if it is something that you are working with, or in the nature if it is a wild plant. Seed stratification is described in many books about flowers and plants, for example, Zimdahl’s book Fundamentals of Weed Science, Third Edition, published by Elsevier. There is also plenty of information and advice on the Internet, for example on this web site. We have tried to make this site accessible to as many as possible, to the benefit of gardeners and their plants everywhere.

What seeds would normally need to undergo the cold stratification process for them to break dormancy and then germinate? The plants that would normally require stratification would include Fuchsia, Hardy Hibiscus, Evening Primrose, Sedum, Ironweed, Hen-and-Chickens, Chinese lantern, Perennial Sweet Pea, False sunflower, Foxtail, Butterfly bush, Catmint, Black Eyed Susan, and Lavender.

Gardeners taking it upon themselves to speed up the stratification process would need to take much needed care in ensuring that any additional material such as seed-pod fragments, cone scales, fruit pulp, and the like are carefully removed from the seeds without removing the shell of the seed they want to stratify. The stratification process can be shortened further by soaking seeds in cold water for at least 6 to 12 hours before it gets placed into a sealed bag or container. Other seeds would need warm stratification which are then followed by cold stratification. This is accomplished by planting the relevant seeds in a mulched garden bed that would be ready for germination during the following Spring season. Some gardeners have a knack for stratification, while others would have to practice to get it right.

Do all plants require stratification? No. You do not have to stratify, for example, anemones:

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Anemones (a spring bulb) does not require stratification. Photo by Özgür Mülazımoğlu.

In summary, seed stratification is a process that you will have to master, eventually, when you progress as a gardener. Browse this web site with its texts, images, and links to learn more and to become inspired. Good luck with your gardening.