Big Pumpkin

The world record for giant pumpkin is over 2000 pounds!!! How can people grow such a large pumpkin?! Alternatively, can you grow a “teeny-tiny” pumpkin over time?

This model provides young students with a simple interface to explore selection and the impacts of environmental factors on plant traits.

Grades: 3-5

NGSS Standards: 3-LS3-1, 3-LS3-2; 3-LS4-2.


NetLogo version: 6.0.2 or higher

1. Start with a pumpkin patch

2. Press button to pick a pumpkin in simulation window and then plant it

3. The buttons below help you find the largest/smallest pumpkin.

4. Adjust water and/or fertilizer levels

5. Plant pumpkins without selection


Model Components and Rules

  1. Variation: In this simulation pumpkins always vary in size and weight. Larger pumpkins are heavier.
  2. Heredity: The pumpkin size is inheritable. Bigger pumpkins produce big pumpkins on average, so do the smaller pumpkins.
  3. Selection: Users may choose to plant a pumpkin with a certain weight. Users may also observe the changes in pumpkin weight when no selection acts on the population.
  4. Environmental factors: Insufficient water or fertilizer will limit pumpkin growth so it will take much longer to get large pumpkins. But too much water and fertilizer will kill the pumpkins.
  5. Life cycle: Pumpkins complete one life cycle within a year.

Other rules:

  • The smallest pumpkin weight is defined as 1 pound so that you don't get a pumpkin that is smaller than 1. This is to avoid getting a negative size over time.
  • The large end of the pumpkin weight is defined as 500 pounds but you can keep going up. The world record is over 2000 pounds !!!
  • Sometimes the largest/smallest pumpkin hides under a leaf. Look for the weight number instead.



  • Introduce the phenomenon: giant pumpkin. Pumpkins always remind young kids of autumn and of course, Halloween. They are amazed to know that the world record for giant pumpkin is over 2000 pounds, basically as heavy as 45~50 elementary students. Ask students how farmers can grow such a large pumpkin. Students can come up with a lot of ideas.


  • Allow students to try out some ideas, such as provide a lot of water/fertilizer, grow a long time, or choose special seeds. At the end of this phase, provide students with a reading about how farmers grow giant pumpkins.


  • Allow students to examine 12-15 pumpkins of the same species, e.g., the small pumpkins from grocery store work fine. Ask students to describe the traits of these pumpkins, especially the weights. Students should realize these pumpkins weight differently.
  • Ask students which pumpkin they would harvest seeds for growing a larger pumpkin next year. When students propose their ideas, have them provide explanations.
  • Introduce students the pumpkin contest simulation. Allow students to explore the simulation for a few minutes. Then let students first discuss how they can grow a large pumpkin in the simulation over time. Let students work in groups to collect data for comparing the largest pumpkin 1) with and without selection and 2) with more or less water and/or fertilizer. Conduct whole class sharing and discussion at the end.


  • Give students a challenge to grow a 500-pounds pumpkin within 30 years.
  • Invite students to consider whether and how they can grow smaller pumpkins over time.


  • Students construct a written argument from the data collected from class activities and the simulation articulating that pumpkins inherit traits from their parents and variation of these traits exist in each generation.
  • Students construct an explanation supported by the data from simulation elucidating that pumpkin traits can be influenced by the environment.



The teaching materials are designed by

April Mitchell, Science Coach, Salt Lake City School District

Lin Xiang, Assistant Professor of Science Education, University of Kentucky

The NetLogo model was developed by Dr. Lin Xiang at Weber State University in 2018. If you mention this model in a publication, we ask that you include the citations below.

Xiang, L. (2018). Pumpkin Contest. Zoology Department, Weber State University, Ogden, UT.