Whenever kids get interested in something, it’s fun to run a quick experiment. A few weeks ago in the park my five year old overheard other kids saying that if you get a pine cone wet it opens up. He told us that, and I said “I’ve never heard that. Let’s test it.”

So, we gathered three pine cones, in various stages of “open-ness.”

We took them home and put them in water for a few days. Here’s what happened.

They actually closed up. The opposite of what we’d been told they’d do.

So, we set them on a counter for a few days. Here’s what happened.

One just opened up a bit. The others opened all the way. So, pinecones close when they’re wet and open when they’re dry. Why?

Female pinecones open and close.  “The scales open when dry because their outer halves shrink more than their inner halves, and they pull away from the cone.” (Source)Before the seed is formed, it is thought that they open up so they can be pollinated. Pollen is wind-borne and can be spread more easily on dry, sunny days. After the seed is formed, they open up on warm sunny days to release their seeds.

More info at: San Diego Union Tribune, Davidson Institute of Science Education.

A fun extension of this experiment: soak pinecones till they close, then put them inside a clear bottle or jar with a narrow neck they just barely fit through. Then let them dry – they’ll open up, and it’s like a ship in a bottle – people won’t be able to figure out how you got the pinecones inside the bottle.