Vernalization: Definition & Process

Instructor: Lauren Posey

Lauren has taught intermediate reading in an English Language Institute, and she has her Master's degree in Linguistics.

Certain plants have very specific growth requirements. In this lesson you'll learn about a process called vernalization, how it works in nature and how to achieve it artificially.

Chill Out, Plants

When you think of flowers, what season comes to mind? Spring! That's when plants grow flowers that will develop into seeds to grow more plants. Many plants do this every year. But did you know that some plants, called biennial plants, only produce flowers every two years? These plants grow every year, but in the first year, they only produce roots and leaves, not flowers. Some examples include beets, onions, winter wheat, cabbage, and turnips.

In order to produce flowers and seeds, these plants have to go through a process called vernalization. Vernalization simply means that the plant has to experience a period of cold before it can produce flowers. It literally has to be chilled in order to reproduce. As a result, it only flowers every other year, so that it has a winter in between its first growth and its flowering stage.

Beets are an example of a biennial plant

Why Wait?

So, what is the purpose of this adaptation? It seems as though producing seeds every year would be better for the plant's goal of reproduction, right?

This adaptation is mainly seen in plants from temperate regions where there are distinct seasons, and it guarantees that the plants will flower at the right time. If they were to flower in the fall the seeds wouldn't have enough time to germinate, or sprout, before winter set in, and the new plants would die.

By requiring a period of cold weather before flowering, the plant ensures that it will flower in the spring and have the maximum amount of growing time. Each plant actually has a set number of hours that it has to be chilled before it can grow. This prevents the plant from sprouting if there is a warm spell in January, only to freeze and die when winter sets back in. Basically, the plants have adapted to ensure that they will survive the winter, and be able to reproduce once spring rolls back around.

Speeding Up the Process

Of course, if you are a gardener or a farmer, you might not want to wait two years to have a new crop. The vernalization process can be artificially recreated so that the plants will produce flowers every year and new crops can happen more frequently. The seeds are allowed to partially germinate, and then they are chilled down to 0 degrees C/ 32 degrees F until it is time to plant. This satisfies the plant's cold requirement and means that it will flower once planted, even if it is in the same year. Artificial vernalization also means that temperate plants can be grown in warmer regions, where the seasonal chill doesn't naturally occur.


Once a plant has been vernalized, it is also possible to reverse the process. This reversal is called devernalization. It is accomplished by warming up the vernalized plant, exposing it to temperatures at or above 26.7 degrees C/80 degrees F. This sets the plant back into its original non-flowering state.

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