Regrowing Green Onions: Easy Preschool STEM Activity

Have you ever thought about using everyday kitchen ingredients for a science experiment? Regrowing green onions (also called scallions) in water is a fantastic way to introduce your preschoolers to how plants grow. It’s simple, quick, and inexpensive. With just a few supplies, you can create an exciting growing project that your preschoolers will love.

Why I Love this Project for Preschoolers

I love doing this project with preschool children for several reasons:

• Adaptable for All Ages: This experiment works well for children ages two to six.
• Quick Results: Green onions regrow in just a few days, sometimes overnight.
• Durable Plants: Green onions can handle being held and observed by young children.
• Affordable: For less than $5, each of my fifteen students could have their own onion to grow.
• Measuring Component: Students can use linking cubes or other nonstandard forms of measurement to track growth.

Background on Green Onions

Green onions, also known as scallions or spring onions, are a variety of onion harvested while the tops are still green and before the bulb fully develops. Although green onions look different from most vegetable plants, they have the same basic parts: roots, a stem, and long, hollow green leaves. On some onions you may observe a small bulb near the roots. 

Materials Needed for

• Scissors
• Rubbing Alcohol and cotton ball
• Green Onions (1 per child)
• Small jars
• Water
• Magnifying Glasses
• Linking Cubes
• Observation Pages (Use your own or Click here to Purchase)

Lesson Preparation

1. Disinfect the scissors by wiping the blades with a cotton ball soaked in rubbing alcohol.

2. Label individual jars with each child’s name.

Lesson Introduction

1. Show the children the scallion and describe the parts, pointing out the roots, stem, and  leaves. 
2. Pass around a plant to give students the opportunity to touch and smell the onion. 
3. If desired, hand out small pieces of pre-cut green onion to taste and ask for their observations.
4. Explain that a plant’s roots grow underground and absorb water and nutrients to help the plant grow. Mention that some plants can regrow even after their leaves are cut off, as long as they still receive water and light.
5. If you have the Growing Green Onions resource, show the class the “Parts of a Green Onion” poster. 

Demonstration: Taking a Cutting

• Show the students how to cut the top off the green onion. 
• Stack two or three linking cubes upright on a table and place the green onion next to the cubes. 
• Using disinfected scissors, rest the blades on the cubes and snip the green onion. The cubes act as a guide for students to know how big their cutting should be. 

Step-by-Step Instructions

1. Fill jars one-third to one-half full of water.
2. Have the students cut a green onion as demonstrated.
3. Give children magnifying glasses to observe their onions and note the layers and roots.
4. Fill out an observation form for Day 1 or simply have your children draw what their green onion looks like today.
5. Place each onion root end in a jar labeled with the child’s name, ensuring the top end of the onion is not underwater.
6. Place the jar in a window that receives indirect light.
7. Change the water every 2-3 days to keep it fresh.
8. Check the experiment daily and note changes on additional observation forms.

Note: If you have extra green onions, place them in the refrigerator to observe later.

Making Observations

• Magnifying Glasses
• Observation Pages
• Pencils, Crayons or Colored Pencils

Hand out supplies to each student.

By the next day, you may notice some of these changes in the green onions:

• The roots around the edge of the green onion may be growing, while the inner roots are not. 
• The inner part of the stem may already be growing. The outer layer should be drying out.
• Each day, you should see more growth and changes.

If you had extra onions that you refrigerated, bring them out daily to compare to the onions in water. These comparisons may bring up ideas for future experiments. Our resource has a blank experiment form for you to fill in and use with your class. 

First, give your students time to use the magnifying glasses to examine their green onion. If they don’t see any changes in the stem, then encourage them to look for changes in the roots. Next, have them compare their green onion with their classmates’ onions to look for differences. Finally, ask them a few of these questions:

• How many cubes tall is your green onion today?
• Did the roots grow?
• Did the stem grow?
• Do you see new leaves?
• What color are the new parts?
• Did everyone’s green onions grow the same? If not, what is different?

Once students have had a chance to look at their onion, they can record their findings on an observation page.

Two-Year-Olds: Set out the magnifying glasses and allow the children to make observations. If desired, set out the linking cubes and allow students to pretend to measure the onions. 

Three-Year-Olds: Set out linking cubes and magnifying glasses and allow the children to make observations. If students want to record their findings, use Version 1 of the recording page.

Four-Year-Olds: Set out linking cubes and magnifying glasses and allow the children to make observations. Use Version 1 or 2 of the recording pages, either as a class activity or with individual pages.

Kindergarten and Up: Set out linking cubes and magnifying glasses and allow the children to make observations. Use Version 2 or 3 of the recording pages. 

How Does Growing Green Onions Fit in with the Scientific Method?

Regrowing green onions in water is a great hands-on way to introduce preschoolers to a simplified version of the scientific method. For example:

1. Ask a Question: Can we regrow a green onion from the roots and a short stem?
2. Make a Hypothesis: If we put a cut green onion in water, then it will grow more roots and a long stem.
3. Conduct an Experiment: Place cuttings in water.
4. Record Data: Use magnifying glasses to observe changes and record finding on observation sheets.
5. Share Findings: Compare cutting with other students. Plant the cutting and take it home.

Extending the Learning: Experiment with Other Herbs

Try this experiment with basil, mint, thyme, or oregano. Mint, basil and thyme root within a week or two, but oregano may take up to a month to see roots.

I hope you enjoy learning about plants and how they grow with this regrowing experiment. If you try this with your class or at home, I would love to hear from you.

I have a blog post about growing basil and growing mint.

Make planning easy by picking up this bundle of plant science experiments from my TPT store.

The children loved this project. In past years, I pre-cut the green onions before class, but I won’t do that again. The children enjoyed the process of measuring the green onion against the linking cubes. Some of the children continued to snip the remaining onion leaves into small pieces, which helped them practice fine motor skills.

When all the green onions had grown for about a week, we decided as a class to plant the onions in our school garden. As we planted the onions, several students reminded me that we would need to water our onions so that they could grow. We continued to water and observe our green onions until the plants were almost two feet tall. 

I love when a science lesson starts as a simple experiment and ends with my students wanting to do and explore more. I hope you will try this with your children. 

My Favorite Resources

Note: I don’t earn any commission from these links, I just want to share items that have worked well for me!

Magnifying Glasses: Toddler or 3’s

Magnifying Glasses: PreK or K