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Why do trees grow so tall?
Plant Adventures Unit | Lesson 3 of 4
Back > Share

Why do trees grow so tall?

Plant Adventures Unit | Lesson 3 of 4
Lesson narration:
English Spanish
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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.

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

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Discuss:

Why do you think the leaves are moving?

plantsmoving

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Discuss:

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

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Discuss:

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

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# Extensions
Below are ideas for extending this topic beyond the activity & exploration which you just completed.
# 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.

# 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.

# 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, and 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 sped up video.

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

Discuss, then watch Cameron's video.

# Distance Learning: Time Lapse of Grass Growing

Instead of growing Grass Heads, you can try this substitute activity!

Show this time-lapse video of grass seeds growing. [5 seconds = 1 day in real time]

Ask your students to answer the following questions:

  • What happens in the dirt on Day 3 and Day 4?
  • What happens on Day 5 and Day 6?

Have students draw what they notice.

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
Credits

Featured Reviews

“The kids were really excited to make their grass heads, and it was especially cool to hear them make connections from the seed viewer lesson to this one. ”
· Tess · Teacher
“We are waiting for them to grow. The surprise that the plant without light grew taller than the others for awhile stumped everyone. Then the "light" went on and they realized it was trying to find light.”
· Elise · Teacher
“We have been loving watch our grass heads sprout! My students have become so confident in making observations because of these hands on activities! ”
· Sharon · Teacher
“It worked much better than last year because we really used a lot of paper towels. Our grass heads were bigger and the grass was healthier.”
· · Teacher
“Love the sped up part that shows the plants moving toward the sunlight and how the roots always can find the way to grow downward.”
· Erica · Teacher
“My students enjoyed this activity. We had to discuss that patience is REQUIRED in this activity for it to come together since they had to work with their partners. Also, immediate results will not happen. When they heard that it may take up to two weeks, you could hear the sighs. LOL”
· Cheryl · Teacher
“ The students loved making the grassheads. They clearly understood that trees grow tall to get the sunlight! ”
· Elaine · Teacher
“The Grass heads look pretty hilarious. We were able to buy disposable nylons (the footies you get at shoe stores) and they worked great! ”
· Ness · Teacher
“The exploration had a lot of great information. The students had great discussions. The steps for the activity were simple and easy for my group of second graders to follow. The students loved it!”
· Crystal · Teacher
“Great to get a reminder email to water the grass heads before the weekend. ”
· Ashley · Teacher
“Once again, the excellent videos and the opportunities for students to share and discuss their predictions made it fast-paced and engaging.”
· Molly · Teacher
“Grass Heads were a big hit!!!”
· Courtney · Teacher
“Fabulous lessons!! I love it so much! These are the best science lessons. The kids stay engaged and even I am learning so much. I also love the activities.”
· Wendy · Teacher
“The best part was that the students did not actually guess the solution to what would happen to the plants in the dark, or why; so they were rapt to find out! For the activity, the excitement over Grass Head was palpable. ”
· Katie · Homeschooler
“They loved seeing how the bean sprout grew towards the sun. We haven't yet done the grasshead, but after spring break we will do that. They can't wait. I loved getting the email reminder to water them...very helpful (even though he hadn't done it yet, I loved the thought).”
· Amy · Teacher
“Love it! I'm trying to find funding for next year!”
· Kelly · Teacher
“We learn something new with each of these lessons. The explorations are very clear and thorough, and the activities are great, too!”
· Eileen · Homeschooler
“My kids loved watching the plants move to follow the sun/light source in the sped up videos. They thought the plants looked like they were dancing!”
· Kira · Homeschooler
“The video and questions were so engaging. We loved discussing what we thought would happen and were delighted to see what actually happen--and discuss that as well. Very well thought out lesson! Thank you!”
· Debbie · Homeschooler
“It was fantastic!”
· Geralyn · Teacher
“My students really enjoyed making the grassheads. Science can indeed be fun!”
· Susan · Teacher
“The kids absolutely loved making their grass heads and watching them grow. I loved how they were able to meet the lesson's objective.”
· Kristina · Teacher
“The grass head was fantastic!! We also loved watching the forest in a year video in the extra section. These lessons have inspired my daughter to start growing her own plants. The bean we germinated in the root viewer weeks ago has now been transplanted into a larger pot and is thriving. She even wanted to visit a nursery and was asking all kinds of questions to the employee and now we know even more about the specific plants we are growing, especially her granny apple seed tree that she also germinated in the root viewer and now is in a big pot as well. We have learned the best kind of minerals to feed the plants for the best results. I am convinced that none of this learning would have happened if it wouldn't have been for your mysteries. Thanks again!!”
· Imelda · Homeschooler
“Students LOVE seeing the fast motion camera of the plants moving toward the sun! Your program is AWESOME!!!!”
· Beth · Teacher
“Great video! Kids learned a lot! Immediately the kids started noticing the trees around us and how they grow differently because of their need for sun!”
· Zahra · Teacher
Lesson narration:
English Spanish

Grade 2

Plant Adaptations

Light, Leaves, & Competition

2-LS2-1

Activity Prep

Print Prep
In this lesson, 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

I have a Mystery Pack

Grass Head worksheet 30 copies
Ceramic Coffee Mug
Used to store the Grass Heads so they can sprout.
Details
3 mugs
Pen
Or a Sharpie. Water-soluble markers will not work.
Details
30 pens
Rulers
30 rulers
Craft Sticks
30 sticks
Paper Plates
30 plates
Paper Towels
60 sheets
Plastic Plates (10")
Used to hold ¼ cup of grass seed for each group of students. You can also use bowls.
Details
8 plates
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
Rubber Bands (#12)
Small rubber bands.
Details
90 bands
Solo Cups (9 oz)
8 cups
Fast Sprouting Grass Seeds
Must be "Fast Sprouting" so that they grow in 1-2 weeks.
Details
2 cups
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
15 socks
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 lesson. 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 Lesson 4.

Exploration

25 mins

Hands-On Activity

45 mins

Grade 2

Plant Adaptations

Light, Leaves, & Competition

2-LS2-1

Slow internet or video problems?
Credits
 
Plants Lesson 3: Why do trees grow so tall?

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