Let’s plant a seed and watch it grow.
This is going to be a looong video!
Just kidding.
That didn’t take very long at all, did it?
We did speed up the video a little bit.
It takes about 60 to 90 days for a short little flower to grow to full size.
Now imagine how long it must take for a big tall tree to grow!
Trees grow much, much taller than flowers.
The tallest trees are the California Redwoods, and they can get up to 300 feet -
over 90 meters!
So how long does it take for a tree to grow?
Some trees grow faster than others.
Trees that live in warm climates grow faster than the trees that grow in the cold weather.
Close to the equator, there are some trees that grow several meters each year!
Pine trees and other evergreens up in the mountains grow a lot slower: more like one
foot - or a third of a meter - per year.
So it takes them a lot longer to grow to their full size.
If you see a seed, do you know what kind of tree it will grow into?
Let’s find out!
Do you recognize this tiny seed, maybe from your lunchbox?
It’s an Apple Seed!
This is an Acorn, and it grows into a mighty Oak Tree.
This is a cone from a Redwood tree.
Did you know that the seeds in a redwood cone need FIRE to help them grow?
That means they have to wait around for lightning to strike.
If you’ve ever made guacamole, you’ll recognize the Avocado pit.
This hairy Coconut grows into a Coconut Palm Tree.
Not all palm trees make coconuts.
Some make other kinds of fruit, like dates!
Yum.
That’s a peach pit!
The seeds from apricots, nectarines, and plums all look very similar.
We call these all stone fruit.
This delicious fruit is hard to eat because it has a giant seed inside - the Mango!
Have you ever stepped on one of these spiky balls?
It’s a Sycamore seed ball.
This kind of seed is called a Buckeye - because it kind of looks like the eye of a deer.
It grows into the buckeye tree, which is a kind of Horse Chestnut.
This giant seed is the Coco de mer, also known as Lodoicea.
This is the largest seed in the world!
So trees start out as seeds, and then they sprout into little seedlings.
Then, when it’s a young tree, with a slender trunk, we call it a sapling.
But then what?
Do you know HOW trees grow up into their full size?
You might think they grow like people, and just get taller and longer all over.
When you grow, your legs grow, and your arms grow, and the middle of your body grows, too
- animals like us grow bigger and taller all over!
But that’s NOT true for trees.
Trees only really grow taller in a few special areas: the roots, and the shoots.
At the very bottom of a plant, underground, at the very tips of the roots, plants keep
growing new cells.
The new cells are added to the ends of the roots.
This is how roots grow longer and longer, to help a plant find water underground.
The same thing happens at the very top of a plant!
We call these parts the shoots.
New cells can appear at the very ends of the shoots.
So trees grow taller by adding more cells at their tops!
Does this mean trees don’t get any taller in the middle?
YES!
I know it’s hard to tell, because trees grow so slowly.
It’s not like we can watch them grow.
That would be even worse than watching paint dry.
Here’s how you can tell that trees don’t grow taller in the middle.
If you make a mark on a tree trunk, and come back years later,
the mark is still in the same place!
It didn’t get any higher off the ground.
That’s because, remember, trees only get taller at their very tips, the shoots.
There’s also growth happening underground, at the roots.
Now that’s how trees and all sorts of plants get TALLER.
But you know, they also get WIDER.
That’s something that CAN happen in the middle for sure!
I bet you know a sign that trees get wider around every year.
TREE RINGS!
Let’s look at a cross section of a tree trunk.
Look at all those rings!
Each year a tree grows, it gets another ring.
We can actually count up the rings to figure out how old a tree is.
And if we look closely, we can understand how trees keep growing wider.
Some of these layers are growing, and some aren’t.
In fact, some of the tree trunk is dead!
What!!?
It’s true.
The very middle, what we call the heartwood, isn’t alive.
It’s sort of like the tree skeleton.
This center part used to be live cells, but over time,they get smushed in and compressed
by the new layers of tree that grow on the outer rings.
The heartwood is usually darker than the rest of the wood, but not always.
Then comes the lighter coloured sapwood, and these layers of the tree are alive.
This is where water and minerals are transported, up and down the tree,
kind of like a circulatory system.
Water and minerals move through a tissue called xylem.
Farther towards the outside of the tree, just under the bark, is where you’ll find the
sap - all the sugary nutrients - moving through a tissue called phloem.
But neither of these make a tree grow wider.
HERE’S the very thin layer where the tree trunk is growing wider by adding new cells.
It’s called the CAMBIUM, and it’s between the xylem and the phloem.
On the outer edge of this layer, cells are added towards the outside of the trunk.
On the inner edge of this layer, cells are added towards the middle!
So the tree is actually getting wider in two directions!
There’s a special name for the parts of the tree that divide and add new cells - meristem.
In the tree trunk, we call it lateral meristem.
Lateral means to the side, and that makes sense, because that’s how a tree gets wider,
by growing sideways.
In the roots and shoots, we call it apical meristem.
This comes from the Latin word apex, which means point or tip.
Does that make sense to you?
Trees grow at their tips, both above ground and below.
So the next time you look at a tree, and think it’s just standing there, you’ll know
that it’s actually very busy, secretly growing taller at its roots and shoots, and wider
inside its trunk.
Sneaky trees!
Do you love these sneaky beautiful trees and want to help them grow?
Your favourite YouTubers have a plan to grow 20 million Trees by January 1st, 2020.
There’s a good chance we can do it, with your help! #TeamTrees is raising $20 Million
dollars with the Arbor Day Foundation to plant 20 Million trees.
That’s 1 dollar per tree.
What a bargain!
You can donate at teamtrees.org and be a part of #TeamTrees!
Ask your grownup for their help.
Or plant a tree at your house or your school.
Just remember, you’re going to have to be patient - because now you know how much work
goes into growing a tree.
Did you recognize the trees we talked about today?
Do they grow where you live?
We’re so lucky to have trees.
Take some time to be with a tree today!
Now it’s Time to watch another SMART + FUN video from Socratica Kids.
You get to pick!