What happens to a rotting pumpkin?

What happens when you let a pumpkin rot?   That was the question proposed by my son last year…so we decided to find out.

Pumpkin Science What Happens to a Rotting Pumpkin

Rotting Pumpkin:

We carved our pumpkin & put it on the porch to greet visitors.
Rotty September 142

After a few weeks, our pumpkin, who Reese named Jack Rotty, began to get a little mushy.   We got a tray for Rotty to sit on so he wouldn’t rot directly onto the porch. We made a journal to record our daily findings. We got to work!

Rotty September 191

Halloween Activity: Journal

Friday, 6:00pm
“Rotty is turning soft like a sponge. It’s got black mold. It’s getting eaten by a bug & looks black and not so good.”

Reese poked his finger into the mushy parts….
Rotty September 192 Reese
Each day, Mom recorded Reese’s observations. I drew the outline of Rotty & Reese colored in the mold spots & mushy parts.   If you have an older child, let them do the recording & drawing.
Rotty September 194

September 13

Saturday, 6:00pm
“Where I stuck my finger it grew mold. The back is all fuzzy moldy. It has bugs. More mold is growing inside. I can’t believe where I stuck my finger got mold!”

Rotty September 227

September 14

Sunday, 7:15pm

Rotty September 238 Reese“It’s rotten. It looks kind of ashy. His mouth is getting all rotten. I see a spider on the pumpkin. There is more mold today. I see bugs. They must be looking for food in Rotty. He feels soft.”
Rotty September 242

September 15
Monday, 6:30pm
“He’s rotten & smells like a dirt pile. His face is all gooey. You can see where I stuck my finger in. Look at all the pumpkin juice! The back is falling & tipping over. I wish Rotty would stay a little bit longer. His color is black & orange.”
Rotty September 305

September 17
Wednesday, 7:15pm
“He is rotten. He is smaller because he’s going down. Inside there’s a lot of mold! It smells like pumpkin to me…and dirt. I don’t see any bugs today. There’s a soft part on his head.”
Rotty September 339

September 21
Sunday, 7:15pm
“He’s so small! Not big & bumpy. You can still see where I put my finger. He’s decomposing. Part is soft from decomposing, but part is hard because it dried up. There’s a fly on him. He must eat the pumpkin. The back is sinking fast!”
Rotty September 305

September 22

Monday, 7:30pm
“He’s not like that anymore…not full. He looks like rotten eggs. He’s all brownish. Look inside…mold! He is small. I see a Junebug in there…it’s laying in Rotty. I see a fruit fly inside…lots of fruit flies!”

Rotty September 498

September 26
Friday, 3:00pm
“He’s not big & tall. He feels hairy. He’s dry. It’s called evaporate. Our guess was wrong. I thought he would turn into goo. We see fruit fly larva from Larva Land. No, really, they came from fruit flies.”
Rotty September 532September 530September 537

Pumpkin Faces:

We loved watching how the face of Rotty got grumpier and grumpier as it aged.   This was a GREAT experiment to do together. It was Reese’s first chance at long term observation, and our record book helped keep track of the changes each time we looked. I had to put a note on Rotty that said “Please excuse our science experiment!” because I was afraid our dear UPS lady would think we’re nuts!

How do you decorate your pumpkins?


  1. HappyCampers says:

    Doing it this year!!

  2. This is GREAT! I think I remember seeing it last year when ya’ll did it; but this is so detailed and great pirctures! In fact, I was laughing my head off as I scrolled down. GROOOOSSSSSSS! But so hilarious; and such a great project. I love love love it. We are TOTALLY doing it this year. Jack (8) will go CRAZY for this!!

  3. Love that you turned something that is normally a ‘groan task’ (i.e. who gets to throw out the rotting pumpkin) and turned it into a science project! So cool!

  4. Great project, I may have to try this with my step grandson, who is 10. I’ll have to find out what they are doing in Science.

    1. HappyCampers says:

      I would encourage you to do it with your grandson no matter what they’re doing in Science! It’s a fun way to see what really happens to those pumpkins after Halloween 🙂

  5. I can’t help but think of you every time I see a rotting pumpkin…in a nice way :).

  6. This is BRILLIANT! I loved reading Reese’s observations and can’t wait to try this with my kids when they’re a it older.

    1. HappyCampers says:

      You’ll have to let us know how it goes!

  7. What a great science experiment – I think mine are a little young at the moment but can’t wait till they are old enough to do something like this (may also use it when I return to teaching as a great science experiment)

  8. my three year old class observed our pumpkin from (2010) decompose, then germinate in the spring (2011), to produce our halloween pumpkin! They used powerful words to describe the process….gross, disgusting, ugly, shrinking, moldy, hairy, germinate, flower, vine, tendril. The pumpkin is about ready to harvest, a life cycle completed!

    1. HappyCampers says:

      That is amazing! What a unique, meaningful experience you gave them. I guarantee they will remember much more about pumpkins & their growing cycle than if you had just read a book & done a cut-and-paste! And talk about learning dealyed gratification!

  9. What a great, but simple idea! Poor Rotty. Thank you so much for linking up to Fun Sparks.

    Emma @ScienceSparks

  10. Big M threw Little M’s pumpkin… it broke (of course). After handing out the appropriate consequences I decided this pumpkin would NOT go to waste. We are on day three of our pumpkin experiment. It’s in a container and we just cut off the top of the pumpkin. The seeds are still in… I can’t wait to see what they think of the results. I have been taking pictures and writing in our family science journal. Having them keep their own picture records is a great idea. I think we’ll start that tomorrow!

  11. This seems so cool, I would love to do this with my little girl. She would love it;-)

  12. What a fantastic idea! I love the fun science that appeals to all kids =-) Thanks for linking up at TGIF! Have a great weekend,
    Beth =-)

  13. This is the one blog which I visit from last two weeks and I really like this and it helps

  14. Hello just wanted to give you a quick heads up and let you know a few of the images aren’t loading properly. I’m not sure
    why but I think its a linking issue. I’ve tried it in two different internet browsers and both show the same outcome.

  15. That is awesome–the story of Pumpkin Jack in real life!

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