Flowering Seeds: Winnowing
Place of Learning: 
Grade Level: 
This food system lesson introducesthe concept that there are processes for getting food to the fork. It can be paired with a science and/or humanities lesson on ancient culture’s methods for processing grains. The activities experiment with different winnowing methods and reflect on how they compare to modern agriculture. You may want to invite students to create a timeline on the history of seed saving in farming.
Student Learning Goals & Objectives: 

Students will:

  • Identify cultures that usedwinnowing.
  • Compare methods of winnowing.
  • Experiment with two winnowing methods.
Materials & Prep: 
  • Sieve, Screens, or Strainers
  • Metal Bowls
  • Small Containers
  • Cloth Sacks
  • Wooden Boards
  • Wheat Stalk with Weed Berries
Procedure Steps: 
Activity Preparation
  1. Collect samples of seeding flowers from the garden. Prepare different stations for winnowing.
Why and When for Winnowing?
  1. Show students a plant with the seeds and the flower intact.
  2. Review flower anatomy, focusing on the seeds found in wheat flowers particularly.
Methods for Winnowing
  1. Ask:
    • Why do we need wheat seeds?
    • How do we process the seeds?
  2. Review the different methods for winnowing seeds:
    • Threshing: Perhaps the most common method. Place seed pods in a pillowcase or cloth sack and thrash (“thresh”) it against a hard surface to break the seeds from their coverings.
    • Pressure: Apply gentle pressure to crack open the pods with boards.Take care not to press so hard you split the seeds.
    • Screening: Separate dirt from seeds with screens orstrainers. Screens with meshes of varying sizes provide a quick way to separate debris from seeds. A single screen is a vast improvement over hand picking. Screens work especially well for seeds (such as lettuce) that do not have pods. A set of graduated screens will cut out about 80% of the hand work. You can build screens yourself or order seedcleaning screens from sources like Horizon Herbs.
    • Wind power: Outside on a breezy day, drop seeds from one container into another and let the wind blow away the unwanted chaff. Use your breath to slightly blow on the seeds at an angle to separate them from the chaff. This method works particularly well for amaranth.
    • Gravity: This works well for round seeds. Use gravity to help roll seeds down a newspaper into a container. The heavier seeds roll down, while the chaff remains behind.
  3. Once the grain has been separated it can be milled into flour, which is used to make bread.
Practice Winnowing
  1. Review past content on whole foods and processed foods.
    • Tell students that whole grains are whole foods, which means they have fiber.
  2. Demonstrate how to collect amaranth or wheat flowers that are seeding in the garden.
    • Students work in small groups to practice winnowing flowers using two of the methods discussed for amaranth, hollyhock, wheat, and/or cosmos.
    • Students compare the chaff of seeds from different plants.
    • Direct them to pair-share with their small groups to explain the differences in detail.
Student Reflection
  1. What are the benefits of modern processing for separating seeds? What are the benefits of ancient winnowing seeds?
English Language Learning (ELL) Focus: Phrasal Verbs
  • Separate from
  • Blow away
  • Roll down
  • Blow on
  • Crack open

Academic Standards

Next Generation Science Standards

Disciplinary Core Ideas


Human Impacts on Earth Systems: Human activities in agriculture, industry, and everyday life have had major effects on the land, vegetation, streams, ocean, air, and even outer space. But individuals and communities are doing things to help protect Earth’s resources and environments.