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Plant Needs: Sunlight

Set up an experiment to test whether plants need light to grow.


  • grass seeds
  • paper towel
  • plastic sandwich bags
  • paper plate
  • bucket (optional)

Key Science Concepts

  • Plants need light to grow.


Emphasize science process words like experiment, test, compare, describe, observe, and prediction.


Ask children, What do you think plants need to grow and stay healthy? Then say, Let’s set up an experiment to find out if plants need light to grow. Have the group set up one experiment together.

  1. Fold two wet paper towels and add each to two plastic bags. Add grass seed to the bags and seal.
  2. Put a paper plate on top of one of one of the bags, blocking light from reaching the seeds. Leave the other bag exposed.


You may also try putting a bucket upside down on a grassy area outside. Ask children to check periodically to see what happens to the grass underneath the bucket. 

Reflect and Share

Ask children:

  • Why did we set up two different bags? What is different about the two bags? How might this experiment show us whether seeds need sunlight to grow?
  • What do you predict will happen?  

Have children document the experiment on paper. (They might draw a line through the middle of the page. On one side they could draw the seeds receiving sunlight; on the other, the seeds covered by the plate that won’t get sun.)

One Week Later: What Happened?

Check on the results of the sunlight experiment.


  • drawings from sunlight experiment
  • markers or crayons

Key Science Concepts

  • Plants have different parts: roots, stems, leaves, and fruit. 
  • A tree is a very large plant. There are many different types of trees.


Encourage children to use science process words such as experiment, observe, describe, compare, predict, and results.


Remind children that it’s been about a week since you set up your experiment, testing whether seeds need sunlight to grow. Have children look back at their drawings of the experiment. Explain that it’s now time to look at the results.

Gather around the sunlight experiment and ask for a volunteer to explain the experiment. Why is one plate of seeds uncovered and one covered by a paper plate? What will this show us? Then take the plate off the covered seeds and ask children to compare the grass seeds on the two plates: 

  • What do you notice about the grass seeds?
  • How would you describe the seeds that got sunlight? How would you describe the ones that didn’t?
  • Have children look very closely at the seeds that were covered and ask if they see any signs of growth. (Depending on what they see, children may conclude that seeds can still grow even without sunlight).
  • What do you think we learned from this experiment?

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