Why do pinecones open and close?
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What do you think happens to the seeds when the pinecone finally opens all the way?
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Transcript
Have you ever seen a pinecone open up, then close tight? Let's find out why!
When rain falls, the pinecone's little scales soak up water and squeeze shut. Closing keeps the seeds inside safe and dry.
When the sun comes out, the scales dry up and curl open wide. The dry air makes the wooden scales bend outward like little doors.
Once open, the wind can reach the seeds tucked between the scales. The wind carries them far away to grow into new trees.
So that's why pinecones close in the rain and open in the sun—it's how they keep their seeds safe and send them off to grow.
For grown-ups: the science
Pinecone scales soak up water and swell shut when wet, then dry out and open up when the sun comes back.
Pinecone scales are made of layers that absorb water differently, causing them to bend. Wet weather makes scales swell and close, protecting seeds from rain; dry, sunny weather makes scales shrink and open, letting seeds fly out on the wind. This hygroscopic movement needs no living cells to work, even on a fallen pinecone.