V for Vernalisation

Bet you didn’t think I had anything for ‘V’ hiding away!

We’re back to the sciencey stuff today with another trip down technical-lane, this time though, we’re delving into something arable-related instead of cows… Vernalisation Requirement.

Vernalisation – Plants or seeds gaining the ability to flower and therefore reproduce, or advancing flowering, by exposure to a period of cold temperatures.

The Farm Dictionary

Before we get to that big word that I’m still not sure I’ve spelt right, we need to talk about Winter and Spring crops.

You might have heard a crop of Wheat being referred to as Winter Wheat or Spring Wheat- that’s because different varieties can be sown art different times of the year.

Winter varieties of different crops…

  • Can be sown from August to February, depending on the variety.
  • Are higher yielding (more grain and straw produced).
  • Are harvested first.

Spring varieties…

  • Can usually be sown from February onwards.
  • Are generally lower yielding (less grain and straw).
  • Are harvested after their Winter counterparts.

Now for the technical part. Why can’t Winter and Spring varieties be the same, just sown at a different time?

Well, I wondered that too. It turns out that Winter varieties have a Vernalisation Requirement, which means the plant has to go through a period of low temperatures in order to trigger flowering later on, and therefore, for it to produce seeds/grain to be harvested.

Different crops and varieties have different vernalisation period temperature, duration and timing requirements. If the temperatures are too low or too high, or don’t stay within the temperature threshold for long enough, no vernalisation happens.

Vernalisation helps delay plants from flowering until the Spring, when there’s less chance of cold temperatures to damage the flowers and the conditions are more suitable for grain production.

If the flowers get damaged too early (before they’re pollinated and fertilised), or there are no pollinators around in the cold, wet days to pollinate the flowers that need them, they don’t produce any grain. In the same way if your fruit tree’s flowers get damaged by a hard frost straight away, you don’t get any fruit that year.

No Flowers = No Grain = No Harvest

And yes, crops like Wheat and Barley flower, just not in the way we’re used to seeing, which I was very surprised to learn!

In Wheat, you can see tiny, yellowish pollen sacs, called Anthers, hanging from the grain-bearing head (ear) of the plant in early Summer. They look whitish and shrivelled, like the ones on the picture below, when the plant’s stopped flowering and is now developing the grains.

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