Register with GEF for FREE to enjoy these great benefits! 

    • member only contests and raffles

    • sustainability program news and updates

    • significant discounts at GEF Institute

Note: If you have problems registering, contact This email address is being protected from spambots. You need JavaScript enabled to view it.


Taking a GEF Institute Course? Login by clicking here.






Join Us

Sign Up for National Green Week!
Please note: Your privacy is very important to GEF. We do not share or sell any of your data.  It is with the sole purpose of providing you with relevant information that GEF will contact you.

Welcome to the Sustainability Lesson Clearinghouse

Here, you can find free sustainability lessons to use in your class and upload your own lessons to share. Be sure to rate the lessons you use and leave comments for your colleagues!

All of GEF's lessons and programs are offered at no cost.  Become a member to support GEF and enjoy member only benefits! 
Join button_03

Professional Development

GEFinstitute LOGO_WEB GEF Institute offers affordable, online sustainability courses eligible for professional development or academic credit.
Give your resume a boost!

Sponsor a Teacher

Support educators in your community by helping them earn a Certificate in Sustainability or take an online course. Find out more about sponsorship!
Sustainability Lesson Clearinghouse

How Many Seeds

Lesson Description:
Students will guess how many seeds are in a cucumber and then count to find out.

  1. Ask the class if they have ever cut open a cucumber? What’s inside? Then ask the class how many seeds they think are in a cucumber. Ask for a show of hands for those who think there are 5 seeds, those who think there are 20 seeds, and about 50.
  2.  Let’s find out: divide the class into groups of two. then cut the cucumbers in half for the students.
  3. Hand out the cucumbers, spoons, and cups for each student. Explain that their job is to remove the seeds and place them into the cup. Once they have removed all the seeds, each group can count how many seeds they have.
  4. Once the students have finished counting, ask them what their total number of seeds was and record on the board. then ask the class what their strategy was for counting the seeds? By 1’s? by 2’s? Also ask if they think the size of the cucumber determines the number of seeds.
  5. Afterwards the students can eat their cucumbers.
  • The activity can be shortened or lengthened depending on the size of fruit or vegetable used. pumpkins are great for a larger activity during October, and apples work well for a shorter activity or during apple picking season.
  • Before cutting the cucumbers, students can measure and record the length and circumference in the widest part of the cucumber.
  • Make more groups and cut cumcumbers into smaller pieces.

Lesson Type:
  • Group Work
  • Other

Sustainability Topic:
  • Gardening

GEF Program Category:
  • Green Thumb Challenge

Time Needed:
30 minutes
Materials Needed:
  • cucumber
  • a knife for cutting the cucumber
  • spoon
  • cup

School or Group:
Contact Email:

The Sustainability Lesson Clearinghouse is brought to you in partnership with

Center for Green Schools