Why does a tomato have so many seeds?

This activity would be a great to do towards the end of a seed unit, once students have already learned about what a seed needs to grow and also seed dispersal.  I love the connections made and the discussions that often happen here, even with very young students.

Start out by asking students to predict how many seeds they think are in a cherry tomato (hold one up to help with the predictions).

Cherry Tomato
Cherry Tomato (Photo credit: Wikipedia)

Record predictions on the board and tell students we are going to look inside a cherry tomato to find out how many seeds.  Cut each tomato in half, so they can explore the insides easily.  For older students, you will need one tomato per student.  If you have younger students, you might want to give each student half, to make counting easier and more manageable.  When I have done this, we usually found between 60-90 seeds per cherry tomato.  I like to hand out little paper plates for the students to use  to spread the seeds out on while counting.  After students finish counting, allow them to record their results on the board for everyone else to see.

Compare predictions with actual amounts.   If your class is old enough, you may want to figure out an average number of seeds per tomato.  If you are working with younger students who counted half tomatoes, compute the number on seeds in one tomato on the board for the students to see (by adding the number’s from each half).

green cherry tomatoes Houston, Tx
green cherry tomatoes Houston, Tx (Photo credit: Wikipedia)

Next, if you have a cherry tomato plant in the garden, inspect it to see how many cherry tomatoes are growing on the one plant (if you don’t have a cherry tomato plant, you may want to show a picture of one and count the tomatoes growing in the picture).    Ask your younger students to imagine how there must be SO many seeds on the plant right now with all those seeds inside all those tomatoes.  For older students, you can compute how many seeds are located on your tomato plant (ave. # of seeds per tomato times the # of tomatoes).

Now you can get so some really rich discussion….

Ask students if they think every single seed will turn into a plant?  Imagine if every seed turned into a plant, what might the garden look like?  Ask students why do they think the plant creates SO MANY seeds? Why won’t some of the seeds turn into plants?  Discuss the possible reasons seeds might not turn into plants (they get crushed and eaten, they land on concrete (no soil), they land in a desert (no water), they land in the water (no air), they land in a shadow (no sun), etc…). Allow input and questions from students, and you’ll be surprised by the connections and understandings they create.

This might be a good point to read “The Tiny Seed,”  by Eric Carle, a book about a seed travelling with a large group of seeds, many of which do not end up growing up as plants, for various reasons.  I like to end the book by saying something like, “good thing the flower created so many seeds, since only one of the seeds survived to create a new plant…”  and then I might ask, what if there was only one seed from the flower?

Any other activities you might add to this lesson?


2 Comments Add yours

  1. Jim Hilton says:

    Interesting way to stimulate young minds. I like how you think 🙂


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