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What does your family do with your jack-o-lanterns after Halloween is over? Most years we just throw them away. But last year we decided to do use our jack-o-lantern do some some Halloween science. An old jack-o-lantern was perfect for showing the kids the process of pumpkin decomposition. Decomposition, also known as rotting, is a process by which organic substances are broken down after death. Eventually, decomposition breaks organic matter down so that it becomes part of the soil again.
Note: You can find more Halloween activities on my Halloween Activities for Kids page.
So a few days after Halloween last year, we made the decision to NOT throw out our jack-o-lantern. Instead, we put our already-starting-to-rot pumpkin into an unused gardening box.
As you can see, even at the one week post-carving mark, the pumpkin was already starting to mold inside.
At the two week mark, the inside had turned black. Further, the pumpkin had started to shrivel and was beginning to collapse on itself.
And at the four week mark, it had shriveled up. By observing this process, the kids were getting a good sense for the process of pumpkin decomposition.
We actually let the pumpkin sit outside for several months. It eventually turned into a flat, hard item that was barely recognizable as a former jack-o-lantern. Sadly, I failed to get any pictures after the 4 week mark, and eventually one of the kids tossed it in the garbage. But we may just give this pumpkin decomposition experiment another go this year to see how it turns out.
If you plan to do this activity, you may also enjoy reading the book Pumpkin Jack by Will Hubbell. It is the story of a boy who carves a jack-o-lantern for Halloween, and then leaves it to rot in the backyard. By springtime, little was left of the jack-o-lantern, as it had mostly decomposed. But then a pumpkin vine began to grow where the jack-o-lantern had rotted, so the life cycle continued.
More pumpkin resources for kids
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