Fall Harvest Math and Science: Pumpkins, Seeds and Squash

Pumpkins and squash are some of the best teaching materials of the year. They are cheap, they are in every shop and farm stand in October, and they pack a surprising amount of math and science into one object. A single pumpkin can cover length, mass, counting, estimating, graphing, plant life cycles and the idea of a fair test.

None of it needs Halloween. Everything below works just as well with a small sugar pumpkin, a butternut squash or a big round one from a farm stand, and it works long after the carving is over.

Start with looking closely

Before any numbers, ask the child to look at the pumpkin for a full minute and describe it. What color is it? Are there ridges, and how many? Is the skin smooth or rough? Is the stem hard or soft? Close observation is a science skill, and the words the child picks (ridged, bumpy, waxy) give you a way to talk about properties.

Then ask a prediction question to keep things lively: “Do you think it will sink or float?” Write the guess down. We will come back to it.

Measure around: length with string

A pumpkin is round, so a ruler will not wrap around it. Use string instead.

1. Estimate first: “About how many centimeters around the middle?” (Use inches if that is what your child’s school uses.)
2. Wrap the string once around the widest part and pinch where it meets.
3. Lay the string straight along a ruler or tape measure and read the length.
4. Find the difference between the estimate and the measurement by subtracting the smaller number from the larger.

The question to ask is: “Why does string work better here than a ruler?” It leads to a real idea: we can measure a curved thing by turning it into a straight one. If you have several pumpkins, order them from shortest to longest around.

For older children, measure the height as well, then compare the distance around with the height. Is the tallest pumpkin always the widest? This links to the measurement topic.

Weigh it: mass in kilograms

Use a kitchen or bathroom scale. Metric first: a medium pumpkin may be 2 to 5 kilograms (about 4 to 11 pounds), and a small sugar pumpkin is often around 1 to 2 kilograms. Record the reading with its unit.

• Hold the pumpkin in one hand and a 1 kilogram bag of rice or sugar in the other. Which feels heavier?
• Estimate first, then weigh, and find how far off the estimate was.
• Compare it with two other objects around the house.

A good question: “Does a bigger pumpkin always have more mass?” Usually yes, but not always, because a large pumpkin can be thinner-walled and hollow while a smaller one can be dense. Children who test this with two or three pumpkins learn that “bigger” and “heavier” are different ideas.

Sink or float?

Fill a big tub or a clean sink and gently lower the pumpkin in. Most whole pumpkins float, because the air spaces inside make the pumpkin less dense than water. Some small, dense squash sink, and if yours does, that is a real result worth recording.

Make it a fair test:

• Try a pumpkin, a butternut squash, an apple, an orange and a potato.
• Write down a prediction for each before you test.
• Record the results in a table: object, prediction, what happened.

Ask: “What do the floaters have in common?” You are heading toward the idea of density without needing the word. For older children, the density lab tool is a natural next step.

Count the seeds, by tens

Scoop the seeds out of the pumpkin onto a tray. Before counting, estimate: is it closer to 10, 50, 100 or 500?

Then count properly. Make piles of 10 seeds. Count the piles by tens (10, 20, 30…) and then add the leftover seeds. A result of 4 piles and 7 left over is 47 seeds, which is 4 tens and 7 ones.

This is place value in its most hands-on form. Younger children practice skip counting and grouping, while older children can:

• Count the seeds in one pumpkin, then estimate how many are in a second, similar pumpkin.
• Count the seeds in one section and multiply to estimate the whole pumpkin.
• Compare the number of seeds in a small and a large pumpkin and work out how many more.

Squash, too: cut open a butternut squash, a kabocha or an acorn squash and compare its seed count with the pumpkin’s.

Make a graph

Data from a whole group of pumpkins (or the same pumpkin measured by several people) is a ready-made graphing project. Try these:

• A bar graph of the distance around for five pumpkins.
• A tally chart and bar graph of “sink” and “float” predictions from your family, class or neighbors.
• A line plot of seed counts from several pumpkins.

Read the graph aloud: “Which is the longest? How many more seeds does this one have?” See our data and graphs topic for more, and the graph maker tool for building one on screen.

The plant side: a life cycle

Don’t forget what the pumpkin is: a fruit that grows from a flower and holds the seeds of the next generation. Talk through the order together: a seed is planted, a sprout comes up, vines and big leaves grow, yellow flowers open, bees carry pollen from flower to flower, a small green pumpkin forms, and it ripens to orange. A seed from that pumpkin can start the cycle again.

Roasting some of the seeds is a nice finish. Rinse them, dry them, toss them with a little oil and salt, and bake at a low heat until golden. Let an adult handle the oven and the knife, and make sure the seeds are cool before children eat them.

A ready-made pack

If you would like the activities laid out as printable pages, the Pumpkin Investigation pack for Grades 1 to 3 covers looking closely, measuring around, mass, sink or float, counting seeds by tens, the life cycle, word problems, exit tickets and a worked answer key.

Safety

An adult should cut the pumpkin and handle any knives. Wash hands after handling the pulp and seeds, and keep the work area dry so no one slips.

Frequently asked questions

Can we do this with squash instead of pumpkins?

Yes. Butternut, acorn and spaghetti squash all work for measuring, weighing and seed counting. Sink or float gives different results, which makes a fun comparison.

What age is this for?

Looking, measuring with string and counting seeds by tens suit ages 5 to 8. Older children can estimate seed totals, compare ratios of mass to size and make graphs of class data.

Our pumpkin sank. Did we do it wrong?

Not necessarily. Pumpkins and squash vary in density, and a dense one can sink. Record it as a real result and ask why it might differ from the ones that floated. That question is what a good investigation is for.