Pumpkin Life Cycle STEM Activity ("Pumpkin Jack")

Autumn is the perfect time of year to learn about pumpkin life cycles.  You can find pumpkins at farmer's markets, grocery stores, and roadside stands.  And... you can even find them in coffees, teas, bread, pies, soups, muffins, and more!  Since pumpkins seem to be everywhere and in everything during this time of year, it makes sense to incorporate pumpkin life cycles into your science lessons in the fall instead of waiting until spring when other plant concepts are taught. Keep reading to learn about a fascinating pumpkin life cycle STEM activity and a popular children's book you can use as a part of your science lessons!

Decomposing Pumpkins Science and STEM Experiment: A STEM and science experiment inspired by the children's book Pumpkin Jack. Learn about the pumpkin life cycles/decomposition. #kellysclassroomonline

Disclosure: Affiliate links to Amazon are included in this post.
All photos in this post are used with the permission of Blakeley Kantor.



Pumpkin Life Cycle

Before starting this STEM activity with your students, it's important to introduce the phases of a pumpkin life cycle to them.  There are many ways to teach these phases, so feel free to teach them in a way that works for you and your students.  Just be sure your students are familiar with these vocabulary words:

  • seed
  • seedling, sprout
  • adult plant
  • vine, blossom
  • green pumpkin
  • orange pumpkin
  • life cycle
  • vine, leaves, roots, stem, blossom

Pumpkin Life Cycle

Other important vocabulary words to review for this STEM activity include:
  • harvest
  • germinate
  • germination
  • decompose
  • compost
  • fungus

Reading Pumpkin Jack

After reviewing the phases of a pumpkin's life cycle, get your students excited by reading Pumpkin Jack by William Hubbard to them.  Pumpkin Jack is about a pumpkin that was discarded outside once Halloween was over.  Throughout the story, readers see the changes the pumpkin went through as it rotted and how seedlings emerged from it in the spring.  Pumpkin Jack is the inspiration for this STEM experiment.

Pumpkin Jack by Will Hubbard

About Pumpkin Jack

Author Summary: The first pumpkin Tim ever carved was fierce and funny, and he named it Jack. When Halloween was over and the pumpkin was beginning to rot, Tim set it out in the garden and throughout the weeks he watched it change. By spring, a plant began to grow! Will Hubbell's gentle story and beautifully detailed illustrations give an intimate look at the cycle of life.

🍎 TitlePumpkin Jack
🍎 Author: Will Hubbell
🍎 Illustrator: Will Hubbell
🍎 Publisher: Albert Whitman & Company
🍎 Date: January 1, 2000
🍎 Pages: 32


Pumpkin Life Cycle STEM Activity

Now that you've introduced the phases of the pumpkin life cycle to your students and read Pumpkin Jack to them, it is time to plunge into this pumpkin science and STEM activity!  

You Will Need


Step One: Getting Everything Set Up

Take the large plastic container and cut a hole large enough to fit your small pumpkin through.  Save that piece.  Add several inches of planting soil to the bottom of the container and spritz with water until damp.  Do not saturate the soil.  Place the pumpkin in the container and replace the top of the container.  You may need to use packaging tape to fasten it in place.

Pumpkin Life Cycle STEM Activity

Step Two: Letting Mother Nature Do Her Thing

Your pumpkin will need warmth and water in order to decompose.  The warmer the air and soil get in the container, the faster your pumpkin will rot.  Place the container in a warm area of your classroom and leave it be.  Don't open it unless you absolutely have to.  Opening it will allow the warm air and moisture to escape from it... which will make it take longer for the pumpkin to decompose.

Pumpkin Life Cycle STEM Activity

Step Three:  Ewww

Throughout the autumn and winter, you will see the pumpkin go through the phases of decomposition.  Fungus and will grow on it and spread to the soil.  As the fungus decomposes the pumpkin, the pumpkin will change colors, shrink, and eventually disintegrate into the soil.  All of this is normal... kind of gross... but normal.

Pumpkin Life Cycle STEM Activity

Step Four: New Growth

Once the pumpkin has disintegrated into the soil, it's time to open the container and let the fresh air in.  (May I suggest doing this outside?  This will be really smelly!)  Cover the remains of the pumpkin and the seeds with planting soil.  Spritz the soil with water until it's damp, replace the top, and wait.  In a week or so, you should see little seedlings emerge!

Pumpkin Life Cycle STEM Activity

Step Five: A Mature Plant

After you see seedlings begin to emerge, you can remove and discard the top of the container.  Keep the container in a sunny window so the seedlings can grow.  Water the seedlings as needed and watch your seedling become mature plants!  

If there are too many seedlings in the container, you can thin out the smallest ones to make room for the others.  Don't throw those small ones out!  You can transplant them into paper cups for your students to grow at home.

Pumpkin Life Cycle STEM Activity

Step Six: Transplanting the Pumpkin Plants

Eventually, the pumpkin plants will outgrow the container they're in and will need to be transplanted.  Depending on the type of pumpkin you used for this activity, its vines can grow up to 20 feet long!  Carefully remove the plants from the container and transplant them into the ground... far away from the playground... or to a raised garden bed.  Continue to water and care for the plants as needed.  Depending on when your school year ends, you may be lucky enough to see some yellow blossom on the plants.

Pumpkin Life Cycle STEM Activity

Additional Resources

🍎 Farmer Christiana from Jones Family Farms talks about the pumpkin life cycle and reads Pumpkin Jack in the video below:



Did you enjoy learning about this pumpkin life cycle activity? If so, check out these blog posts about more STEM projects:

75 comments:

  1. Loved the experiment… just wanted to confirm with you do we have to leave the seeds in the pumpkin while carving or no seeds inside?

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    1. Thanks, Meenakshi! You can really do it either way. If you plan to use the pumpkin for Halloween, save the seeds and put them back in when you're ready to seal the pumpkin into the container.

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  2. I have so many questions, but one is, what is the perfect sized snack jar? I have walmart pick up available but don't want to get something too small!

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    1. That's a good question! As long as the pumpkin fits inside of the container, it's all good. Quite often farmers will sell their runty pumpkins inexpensively because everyone wants the big pumpkins. Buy your container first, then find a pumpkin that fits inside.

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    2. What size container/container source did you use? I have been planning on doing a modified version of this with my toddlers, but so far have been extremely dissatisfied with the largest container I was able to source for this.

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    3. Hi LRose. I recommend using one of the big plastic containers that cheeseballs or animal crackers come in. There is a link in the materials list for an example of what to look for. It's easier to buy the container first, then buy the pumpkin to fit inside it. I hope this helps! :D

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  3. Do you have to carve it for this to work?

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    1. Hi Katie. Thanks for your question. It is possible to do this with an uncarved pumpkin, however, the decomposition process will be slowed dramatically and your students may not see the entire pumpkin life cycle before the school year ends. This science experiment works best with carved pumpkins because the warm air and moisture will be able to start decomposing the pumpkin from the inside as well as the outside. I hope this helps! :D

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  4. We are doing this for our home school my son picked little white pumpkins will that work and can we use a large glass pickle jar

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    1. Good question! I don't know anyone who has used a white pumpkin for this science experiment... we just don't see them often in my area. But if you follow the process in this post, I don't see why it couldn't work. If I find out, I'll reply back to you in the comments.

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    2. We did white pumpkins and it worked!

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  5. I noticed someone used a small container w/a latching lid. Would that be ok??

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    1. Yes! As long as the pumpkin fits in the container and you keep the lid of the container closed tightly, it'll work! :D

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  6. Can I use a glass container? Thanks

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    1. As long as the glass container has a lid that will close tightly, it'll work! :D

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  7. Hi! About how long until I can get to the sprout stage?

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    1. Hi! It can take several months for them to grow. Decomposition can be a long and slow process.

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    2. I put my pumpkin in the container at Halloween, it's April 7 and we just got our first sprouts! So exciting! He didn't decompose all the way into the soil, but we have sprouts poking up through the brittle shell.

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  8. Hi! I'm doing this in the library with my PK-2nd grade classes. I have one class each day and last week each class per grade decided upon the shape of the cut I made. I'm waiting to put the dirt in after decomposition - Hopefully this works. Kids thought it interesting to see the pumpkin mouths start to "drool"!

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    1. That is a cool idea! Please let me know how it goes... I want to hear about the drooling pumpkin!!!

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  9. will this stink up my entire classroom?

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    1. Hahahaha! Good question! The only way it will stink up your classroom is if you fail to seal it with the tape properly or if one of your students cracks the seal.

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  10. How long did your pumpkin take to decompose, and start to sprout?

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  11. Good afternoon! Our pumpkin is at the stage to be covered, and I just had a couple of questions. First, how much soil would you recommend? And second, there is a lot of "juice" at the bottom. Is that normal?? Thanks!

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    1. Wow! That was fast! My pumpkin this year is still in the decomposing stage.

      When you are ready to add more soil to yours, add between 1/2 and 1 inch. (It doesn't have to be exact.) The 'juice' in the bottom is full of nutrients... don't dump it out! Some people call it 'compost tea.'

      Leave the top off of the experiment to allow some of the liquid to evaporate. Since the soil in the container is already 'juicy,' let your new soil absorb some of that moisture as well. No need to add more water yet. If the soils stays really juicy, you can drain off some of the water to prevent the seeds and seedlings from rotting. At this point, you can take care of your seeds the same way you'd take care of a houseplant. Keep me posted with your progress!

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    2. Okay, perfect! Thank you so much for your reply. :)

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    3. Mine has a lot of liquid as well! I have about 1 1/2" of soil and the liquid is about 1" above that! I hope we can still grow a pumpkin:)

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    4. That's a lot of water! Since you have so much water, go ahead and ladle it out. You want the soil to be moist, not swampy. After you ladle it out, add some more soil to any excess moisture. If you have seedlings, you can leave the top off it and grow it like a houseplant. Good luck!

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  12. When do we know that the pumpkin is ready to be covered with soil? My pumpkin is completely covered in white.

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  13. My pumpkin is not decomposing. It started too but has stopped. The mold that covered the pumpkin has disappeared and it looks like the day we put it in the container other than being black in a few spots. Did I do something wrong? What do I need to do at this point?

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    1. Hi Sherry. Your question stumped me, so I had to google it. As best as I can determine, your pumpkin might have something called black rot. This is what I found so far: "Black rot – One of the more prevalent diseases resulting in pumpkin or squash rotting on the vine is called gummy stem blight, or black rot, and is caused by the fungus Didymella bryonia. This disease is particularly fond of pumpkins and squash, so if your pumpkin fruits are rotting, this is a likely culprit." I'm still googling if black rot will prevent any seedlings from growing. It sounds like you didn't do anything wrong at all. It's possible your pumpkin had traces of this fungus when you purchased it.

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    2. This happened to me one year and I thought that it might be a genetically modified pumpkin. Since then, I have always purchased organic pumpkins and they work perfectly!

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  14. I'm doing this with my second graders and they are loving seeing all the changes so far. We are on stage 3, and watching it decompose is going to be so much fun! My students named our pumpkin, Jack Jr. 😆☺️

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    1. Jack Jr.! I love it! I'm glad you and your students are having fun with this!

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  15. Hi! I am a 7th grade science teacher and we started our pumpkin in August. It is now January and the pumpkin is still decomposing but the soil is completely saturated and very wet. Is this normal? Should I do something to fix it? Thank you so much for any help or advice you can give me.

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    1. Hello! The soil in your container should be moist, but not saturated to the point that there is standing water in it. If there is standing water in your container, it's OK to remove the lid and ladle some of it out. What does your pumpkin look like now? Are there signs of seedlings trying to emerge?

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  16. We never did end up with a lot of white mold... but now have three sprouts quickly popping up... we never added more soil, other than what we started with... can I leave the lid on till we have more growth and put it more in the sun?? we can still see the stem and the skin of the pumpkin, this has been a fun project so far, any further suggestions?

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    1. Good questions! At this point, you can take the lid off, add a thin layer of soil over what's left of your pumpkin, and take care of the seedlings in the same way you'd take care of a regular houseplant... warmth, water, and sunshine. If your room is a bit chilly because of the winter, you can keep the lid the container and move it into the sun to give the seedlings a bit more time to mature.

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  17. Hi! Thank you for this idea. Our pumpkin has been decomposing since just after Halloween. There are some juicy puddles in the bottom with lots of tiny little white bugs! Have you seen this before? Should I air it out? The pumpkin is pretty squished down now, but the top hasn't decomposed enough to see the seeds---although I do see one starting to germinate and push up. Recommendations? Thank you!

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    1. Hi Anna. It's October and I only now saw your post. Somehow, it landed in my spam folder. The little white bugs you mentioned could have come from the soil or from the pumpkin itself. Were they fruit flies?

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  18. We have loved this project in 2nd grade! We are on week 20 of the project. I had a seedling and it died. I don't have any other seedlings. All that is left is a remnant of a stump. Should I open it up? I don't have any liquid on top, either. Wondering if I did something wrong? Thank you!

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    1. Hi Courtney. It's October and I only just now saw your comments. Somehow it landed in my spam folder. It doesn't sound like you did anything wrong with your pumpkin.

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  19. Hi Kelly- We started in October. Our pumpkin went through the decomposition phase, but I have no sprouts or seedlings! The container has remained sealed. Any thoughts?

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  20. If I were to use a large animal cracker container as suggested can you explain why I wouldn’t just unscrew the lid and put it back on as needed? Why do you cut the bottom off and use it upside down?

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    1. If your pumpkin is small enough to fit through the opening of the container, then you don't need to cut the top of it off. Quite often people buy pumpkins that are too large for the opening.

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  21. I noticed you say that a carved pumpkin decomposes faster. I'm wondering do we remove all of the seeds or do you leave some for the sprouting? Planning to do this in October for the first time.

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  22. I noticed that you said the pumpkin will decompose better if it's been carved. Should I be leaving some of the seeds inside? Excited to try this in October.

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  23. So I have started this project, our pumpkin has been decomposing for about three weeks now. Did anyone else get build up of water in the container, if so did you empty the water out? The water level is now above the level of where the seeds would be the pumpkins has not completely decomposed yet does have some white mold,but has shrunk down some.

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    1. This can happen when you have a 'juicy' pumpkin. If it's a little bit of water, you can add some more soil to absorb it. If it's a lot of water, you can ladle the excess water out and let the soil dry out a bit before replacing the lid. I hope this helps!

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  24. Hii! So I did this project for my son this year for homeschool! So we used a pumpkin that was a little bit bigger than the example, it’s in the container with about 3 1/2- 4 inches of soil. It has been in the container for about 3 weeks. It is now decomposing, has white mold, and the pumpkin has shrunk down/folding in on itself. But the water from the decomposing, is now above the soil and level if not higher where the seeds are in the pumpkin. Should i empty the water out and reseal the pumpkin. I am just concerned that with that much water the seeds will not grow and with being sealed tight how will the large amount of water evaporate? Thoughts or suggestions appreciated!

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    1. You can definitely open the container and ladle out the standing water. Since the soil is completely saturated, you can leave the lid off for a bit to let the excess moisture evaporate before resealing the container.

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  25. Does it need to burped at all because of the gas that is created during decomposition?

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    1. Not usually. But if you have a huge build up of gas, it's OK to burp it.

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  26. Can I cut up the pumpkin into fourth's? Or does it have to be whole?

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    1. That is an interesting question... something I haven't considered. I've only used whole pumpkins in the past. I don't see why using fourths couldn't work. If you try using fourths, please let me know how it goes. You've piqued my curiosity!

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    2. We just started ours and I opted to cut the pumpkin into fourths instead of cutting our container!
      We'll see how it goes.

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  27. Hi.. this sounds great! Is it possible to use a large standing ziploc bag for this experiment?

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    1. Good question, but I don't know the answer to it. In theory, it seems like using a quality Ziploc bag should work. If you try it, will you let me know how it goes?

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  28. Hi, does it need light, or can I put it in a dark pantry?
    And if my son wants to take it out now and then to see, is it OK to be moved around?
    Thanks!

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    1. It won't need light until you can see the seedlings emerge from the soil. Once you see the seedlings, you should move the pumpkin to the light. It's OK if your son moves the container around to see what's happening. Just make sure the lid stays secured so the moisture doesn't escape.

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  29. My pumpkin Jack is covered in all different types of mold. Do you have a suggestion on where I can find out what types of mold is on it?

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    1. Good question! The website Wide Open Country has a list of 12 common types of mold with photos of each.

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  30. Hi, our pumpkin has been in the container for three weeks now. It has a lot of white fuzzy mold on it. It also has some yellow spotty mold and blackish looking mold. There is also something red on it that looks like blood. I’m not sure what it is. Is this normal?

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    1. That is definitely unusual. I wonder if there was an insect of some sort inside the pumpkin or in the soil you used? I'll have to do some searching online to see what that red substance could be.

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  31. So our pumpkins have no mold whatsoever ever. We have been decomposing for 40ish days. They are squashed and leaking fluid but that’s it. No mold…. Why? The container is also caving in a bit! Help?! How do I get mold?!

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    1. The mold isn't necessary as long as the pumpkin continues to decompose. If there is a lot of fluid, it's OK to open your container and drain the fluid. Are there signs of seedlings yet?

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  32. Help! We are in step 3 of the process and it has tiny organisms or bugs.
    Is this normal??
    It’s in a plastic container cut and then taped closed.

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    1. It sounds like there may have been organisms in the soil or inside the pumpkin itself. Although unusual, it's not terrible. If you'd like, you can open your container outside and release the bugs.

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  33. Mary WaldmannJanuary 10, 2023

    Hello, I made the mistake of cleaning my pumpkin way too well for Halloween and there were only 3 seeds in it when I started this experiment. Do you think we have a chance of getting sprouts ?

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    1. It's possible, but unlikely. If you don't get seedlings from one of those seeds, you could be sneaky and plant a couple of store bought seeds in the container. That way the children can still witness the decomposition of the pumpkin and the emergence of seedlings.

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