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What is Nyctinasty?

Why do Flowers Close at Night?

Why do flowers close at night nyctinasty


Simple definition:  The movement of leaves or petals in response to light; the closing of flowers at night. This may help to protect the pollen from dew.

I love learning about amazing things that happen right under my nose. Many of us have observed the way our dandelions are closed up tight in the morning and then the bloom opens up in the sunshine each day. But, have we taken the time to really understand how that happens and why it happens? Just recently I did a little research to find the answer to that question.  Now when I take note of my sleepy little flowers, I can appreciate the mechanism for this phenomenon: nyctinasty.

Poppy nyctinasty

Examples of flowers that open and close:

  • Tulip
  • Crocus
  • Dandelion
  • Poppy
  • Daisy

Fun fact – The leaves of some plants, like those of certain legumes, open and close as well.

 dandelion nyctinasty

Try This! Something to Observe

Find a patch of daisies or dandelions in your yard. Observe the flower at different times of the day. When are they opened up? When are they closed?

Advanced study: For an additional experiment, try covering a dandelion with a box to shut out the light. What do you think you will find when you take the box off the next day?

Taking time to notice these changes will help your child make a more intimate connection with the world around them. I guarantee you will look at dandelions differently after observing them up close!

Nyctinasty notebook page

If you’re an Ultimate or Journey level member here on the Handbook of Nature Study, you have a custom notebook page for creating a nature journal entry for nyctinasty in your download library.

tulip nyctinasty

Additional Links:

Why do plants close their leaves at night? – Audio explanation of nyctinasty.

Flowers on the Move – Super simple explanation of nyctinasty.

List of Flowers That Close at Night – Here’s a list to get you started.


Outdoor Hour Challenges for Flowers That Close At Night


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Ultimate Naturalist Library September 2017 @handbookofnaturestudy