Why do trees grow so tall?
Scroll for prep
Full Screen
Exit Full Screen

Predict:

After 2 weeks, what do you think will have happened to the plant in the dark compared to the plant in the light?

Turn to someone next to you. Tell them your prediction and your reason why.

Full Screen
Exit Full Screen
Full Screen
Exit Full Screen

Discuss: Why might the plant in the dark have grown taller? Look closely at the plants to see if there are any clues.

Full Screen
Exit Full Screen
Full Screen
Exit Full Screen

Discuss:

Why do you think the leaves are moving?

plantsmoving

Full Screen
Exit Full Screen
Full Screen
Exit Full Screen

Discuss:

How can a tree get more sunlight when a lot of other trees are starting to get in its way?

Full Screen
Exit Full Screen
Full Screen
Exit Full Screen

Discuss:

So now if someone asked you, "Why do trees grow so tall?" how would you explain it to them?

Full Screen
Exit Full Screen
Full Screen
Exit Full Screen
Full Screen
Exit Full Screen
Full Screen
Exit Full Screen
Full Screen
Exit Full Screen
Full Screen
Exit Full Screen
Full Screen
Exit Full Screen
Full Screen
Exit Full Screen
Full Screen
Exit Full Screen
Full Screen
Exit Full Screen
Full Screen
Exit Full Screen
Full Screen
Exit Full Screen
Full Screen
Exit Full Screen
Full Screen
Exit Full Screen
Full Screen
Exit Full Screen
Full Screen
Exit Full Screen
Full Screen
Exit Full Screen
Full Screen
Exit Full Screen

Extensions

Below are ideas for extending this topic beyond the activity & exploration which you just completed.
Full Screen
Exit Full Screen

Extra Activity:

How to Train a Bean Plant

In this Mystery, we showed photos of a bean plant that we grew here at Mystery Science. We planted the bean in a cardboard box with a hole in it. The bean grew toward the light, snaking its way toward the hole to escape the dark box.

You can duplicate this experiment in your classroom. Just follow these detailed instructions on the website of the Chicago Botanic Garden.

Full Screen
Exit Full Screen

Time Lapse Video:

A Year in the Forest

In less than three minutes, this amazing video shows your students how a forest changes over the course of a year. This can be used as an interactive classroom exercise in observation. Ask students to raise their hands when they know what season it is in the forest. Stop the video when enough hands are up, then ask students to explain what clues tell them the season.

Full Screen
Exit Full Screen

Video: What will happen if...

Third grader Cameron Wright wondered what a plant would do if she moved the light shining on it. So she decided to experiment.

She got a plant light, planted some peas, & set up a camera to take a picture every 2 minutes. Every 12 hours, she moved the light from one side of the plant to the other. Then she put the pictures together to make a speeded up video.

What do you think the video shows? What does the plant do?

Discuss, then watch Cameron's video.

Full Screen
Exit Full Screen

Image & Video Credits

Mystery Science respects the intellectual property rights of the owners of visual assets. We make every effort to use images and videos under appropriate licenses from the owner or by reaching out to the owner to get explicit permission. If you are the owner of a visual and believe we are using it without permission, please contact us—we will reply promptly and make things right.

Exploration
4 leaves by Vinayaraj
Forest by OSU Special Collections & Archives
Tree trunk by Tomwsulcer
Trees and sunset by Steve Partridge
Dead sprout by Imgur
Huge tree trunk by Allie_Caulfield
Looking up at tree leaves by David Patte/U.S. Fish and Wildlife
Plant growing in cup by Kirsty
Tree and sunlight by FotoDutch
Few patches of sunlight by Joshua Mayer
Looking up at trees by Rowan, Dick, Photographer
Spiral leaves by Just chaos
Canopy by Phil P Harris.
Ferns in forest by National Park Service
Tree soared into sky by Bradluke22
hole in box by Harris Sisters (Donna)
Dinosaur by LadyofHats
plant in box by Kathy J
Sun shining through trees by Richs5812
dark forest floor by Jim Barton
seeds in a cup by Kirsty
Beans in dark box by Imgur
Light/dark growth by Kirsty
Seed sprouts in cup by Kirsty
sun flowers by ajgarrison3
Calendar by Imgur
Leaves by Hana Kirana
Print Prep
Activity Prep

In this Mystery, students will learn the importance of sunlight to plants, which is collected by their leaves. In the activity, Grass Head, students make a person out of a paper towel and a popsicle stick with grass for hair! Then, students make predictions about the direction that the grass will grow based on the orientation (standing up or lying down) that they place the Grass Head.

Preview activity

Number of students:
Ceramic Coffee Mug
Used to store the Grass Heads so they can sprout.
Details
3 mugs per class
Pen
Or a Sharpie. Water-soluble markers will not work.
Details
1 pen per student
Rulers
1 ruler per student
Craft Sticks
1 stick per student
Paper Plates
1 plate per student
Paper Towels
2 sheets per student
Plastic Plates (10")
Used to store the Grass Heads so they can sprout. Plates must have raised edges so they’ll hold water.
Details
4 plates per class
Plastic Plates (10")
Used to hold ¼ cup of grass seed for each group of students. You can also use bowls.
Details
1 plate per group
Rubber Bands (#12)
Small rubber bands.
Details
3 bands per student
Solo Cups (9 oz)
1 cup per group
Fast Sprouting Grass Seeds
Must be "Fast Sprouting" so that they grow in 1-2 weeks.
Details
1 cups per group
Nylon Kneesocks
Ten pairs is enough for 40 students because each student needs half of a nylon. You will cut each nylon in half during activity prep (see below).
Details
1 sock per pair
Grass Head printout 1 per student
Prep Instructions

Each student will make their own Grass Head, but will need a partner to help with a few steps. Homeschool students can work on their own, but will need a partner to help with a few steps.

You will need access to water and a sunny windowsill for this activity.

Label Four of the Plastic Plates

Label two of the plates “Face Up.” Label the other two plates “Face Down.” The other plates will be used to distribute grass seeds to groups of students and do not need to be labeled.

Prepare the Nylons

This step takes about 15 minutes. Cut the stockings in half and tie the open ends as shown in this video.

Fill Cups with Water and Plates with Seeds

For each group of four students, fill a Solo cup with water. For each group of four students, fill a plastic plate or bowl with about ¼ cup of fast sprouting grass seeds.

Keep Your Grass Heads Watered & Hold On to Worksheets (After Class)

Store the Grass Heads in the ceramic mugs and the plates labeled “Face Up” and “Face Down” while you wait for the grass seeds to sprout.

The paper towel of the Grass Head will soak up water and keep the seeds wet — but only if part of the paper towel stays wet. Make sure to keep a water supply in each plate and cup so your Grass Heads stay wet. Grass Heads can soak up lots of water.

It will take 1-2 weeks for your Grass Heads to sprout, so plan accordingly. Your class will examine your Grass Heads during the next Mystery. You’ll talk about whether students’ predictions were right, so collect student worksheets and keep them safe until the next lesson. Students may also find a surprise! For more on that, see the Activity Prep in the Grassheads Revisited activity in Mystery 4.

Extensions
Download this Mystery to your device so you can play it offline: