Hi there! Have you ever noticed how the leaves change color and fall off the trees when it gets colder? It’s such a beautiful sight, especially in places like Seoul, Korea, and Vermont in the United States. Maybe you can see these amazing fall colors where you live too!
Today, we’re going to answer a question from someone named Henry. He asked, “Why do all trees lose their leaves in the fall?” That’s a great question, Henry!
Not all trees lose their leaves in the fall. Some trees, called deciduous trees, do lose their leaves. These trees have broad leaves, and when winter comes, they look bare. But other trees, like evergreen trees, keep their leaves all year round. Evergreen trees have thin, needle-like leaves.
Let’s think about why some trees drop their leaves. Imagine a big snowstorm. The broad leaves of deciduous trees can catch a lot of snow, just like tiny snow catchers. If too much snow piles up, it can weigh down the branches and even break them! So, deciduous trees drop their leaves to avoid this problem.
Evergreen trees, like pine trees, have thin needles instead of broad leaves. These needles don’t catch much snow. In fact, they often point downward, so snow slides right off! This helps keep the branches safe from breaking. That’s why evergreen trees can stay green all year long.
There’s another reason trees drop their leaves. The green parts inside leaves are important for the tree, but freezing temperatures can damage them. So, trees pull the green material back into their trunks in the fall to save it for later.
So, in summary, deciduous trees drop their leaves to protect themselves from heavy snow and ice, while evergreen trees keep their needle-like leaves because they don’t have the same problem. Isn’t nature amazing?
Thanks for the great question, Henry! Remember, there are always more mysteries to explore. Stay curious and keep asking questions!
Leaf Collection and Observation: Go on a nature walk with an adult and collect different types of leaves. Try to find both broad leaves from deciduous trees and needle-like leaves from evergreen trees. Once you have your collection, compare the leaves. What differences do you notice? Which leaves do you think would catch more snow? Why do you think that is?
Tree Journal: Choose a tree near your home or school and observe it over a few weeks. Draw a picture of the tree each week and note any changes you see. Does the tree lose its leaves? Does it stay green? Write a short story about what you think the tree is doing to get ready for winter.
Role Play: The Life of a Leaf: Pretend you are a leaf on a deciduous tree. Act out what happens to you during the fall and winter. Why do you change color? Why do you fall off the tree? Now, pretend you are a needle on an evergreen tree. How is your story different? Share your role play with your family or friends and explain why leaves fall from some trees but not others.
Sure! Here’s a sanitized version of the transcript:
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(phone rings) – Hi, it’s Doug. I love the fall. It’s the time of year when it starts getting colder and many people head outside to catch a glimpse of the leaves. The colors of the fall leaves are absolutely beautiful in places like Seoul, Korea, and Neka, Iran, as well as in Vermont and the Northeastern parts of the United States. Maybe you live in a place where you can see some amazing fall colors in your area.
Someone named Henry has a question about leaves. Let’s give Henry a call now. (phone rings) – Hi, Doug. – Hi, Henry. – I have a question for you. Why do all trees lose their leaves in the fall? – Ooh, that’s a great question. Some trees completely lose their leaves in the fall and look bare by winter, but others don’t. Why is that?
Well, I think the best way to answer this question is to look more closely at which trees lose all their leaves and become bare in the winter, like these, and which ones stay green, like these. One pattern you’re going to notice on the trees that don’t look bare in winter is that they tend to have leaves that are much narrower and thinner than most other leaves. We call them needles.
Trees like these, which don’t drop their leaves in winter, are called evergreen trees. Pine trees are probably the most famous of the evergreen trees, but there are other evergreen trees too, like Junipers, Cedars, and Redwoods. Trees that do drop their leaves in the fall and go bare in winter always have leaves that are broader in shape. We call them deciduous trees, from the ancient Latin word “decidere,” which means to fall down.
So what’s going on? Do you think the shape of the leaves could have something to do with whether they drop off in the fall or not? Now would be a good time to pause the video and discuss.
Okay, you ready? Well, here’s an interesting clue. You see the snow falling on these branches? This can cause problems for a tree. Because the leaves on a deciduous tree are broad, if there’s a snowstorm or an ice storm, the snow or ice can collect on them. It’s almost like the leaves are mini snow catchers.
Now, a little bit of snow or ice on one leaf doesn’t weigh very much, but add up all the leaves on a tree, and there are thousands of them all catching ice and snow. All that snow can really weigh the tree down until branches start to break. That’s not good. So it seems that one reason that trees with big leaves in cold places might drop their leaves in the fall is to prevent snow or ice from accumulating and breaking their branches.
Now, let’s compare that to evergreen trees. Look how thin those needles are. Snow and ice aren’t going to pile up on them like they do with broader leaves. A lot of evergreen trees have needles that point downward, almost like a slide, so that the snow can slide right off. Having thin needles keeps branches from getting weighed down and breaking off, which is great for the tree. Since the leaves are safe, there’s no reason to drop the needles, and the evergreen tree can stay green all year.
There is more to why some trees drop their leaves than just protecting their branches during the winter. For example, scientists have discovered that freezing temperatures alone can damage the green parts inside the leaves, which are important for the tree. This is why most trees will pull the green material from their leaves back into their trunk in the fall to save it.
So in summary, evergreen trees have thin, needle-like leaves that keep snow and ice from piling up and damaging branches. Since these leaves don’t need to drop off in the fall, evergreen trees can stay green all year.
That’s all for this week’s question. Thanks, Henry, for asking it. We’ll be back with a new episode in a couple of weeks. But in the meantime, here are some older questions from the question jar. You can vote on which one you think we should send out next week. You can choose from: what’s that red thing on a turkey? Why are pumpkins so popular every fall? Or, why do people eat turkey on Thanksgiving? So submit your vote when the video’s over. We want to hear from all of you watching. There are mysteries all around us. Stay curious and see you next week.
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