If you are looking for a simple fall nature experiment you’ve got to try this one! We always have amazing pine cones that cover our yard. This spring, during a random flooding event, we ended up painting pine cones to pass the long day of no school. Aren’t they pretty? But….notice anything strange about them?
They are all closed! They had been soaking in a torrential rain downpour for days when the picture was taken. This realization reminded me of the pine cone experiment that I had seen here. So we decided to conduct our own experiment to see how long our pine cones would take to close.
How to do it?
- Choose a few open dry pine cones
- Fill a jar or vase with water and place pine cones inside (don’t worry if they aren’t fully submersed)
- Guess how long they will take to close up
While we were waiting we decided to find the seeds in a third pine cone. Can you spot them? 
After about 10 minutes we went back in to check on our pine cones and lo and behold they had closed up!
Before After 10 minutes
What’s the science?
Pine cones are hygroscopic which means they soak up water from their surrounding environment (like humid air or rainwater). The cells located at the bottom of the cone’s scales absorb water and that pressure is enough to move the rest of the scale forward. This amazing feature of the cone helps the seed come out when it is dry and warm and stay protected within the cone when it is wet or humid. Who knew pine cones could be so interesting!?
I hope you enjoy this simple experiment and discover all the fun science you can do out in nature!
Hello. I found your blog by chance as I was searching the web to see how this could have occurred: At the free store, I had picked up a basket of very old pine cones, that were dried and in the open position, and they have been in the house for several years. (Someone had even painted the tips – a practice I do not understand – applying the unnatural to the natural..).
In any event, I set one of the pine cones outside the other day, facing up, as it looked so much like a Christmas tree. It rained. Today, to my astonishment, the pine cone was completely closed. So, the question is this: how could the cells have stayed viable, allowing for the – hygroscopic is it? – absorption? These cones could well be many decades old. (I wish this would work with my dried out skin). Thank you.
Pretty amazing isn’t it? I am just as surprised as you that pinecones that are decades old will still demonstrate a hygroscopic capability. I also found this article on fossilized pinecones millions of years old with surprising functionality! https://www.nature.com/articles/srep40302
Thanks for this article. I had collected a bunch of large pine cones for a crafting project. I decided to disinfect them with water and a bit of bleach. I inadvertently left them soaking for about 2 hours. When I went to take them out they were all closed up.
I was glad to find that they will open up again once they are dry.
You are so welcome…I had a similar experience. Who knew a craft project could turn into a science experiment? Enjoy!😊