Why do leaves change colours?

October 4, 2006 at 9:56 pm 26 comments

I see this tree everyday and I am fascinated at how only one side of it is turning yellow.


I know that some trees turn colours earlier than others


but usually the changes are scattered throughout the tree.


Or sometimes it’s the top part that usually turns yellow or red first.


But the tree in the above photo, it’s just that side.  I thought that maybe it’s because that’s the side hit by sunlight the most.  But then again, I remember learning in Science that it is sunlight that gives leaves their green colour, the chlorophyll, through the process of photosynthesis.  So it didn’t make sense to me that the leaves on that side were the ones turning yellow first.   

I found myself googling the reason why leaves turn colours.  This is what I found out on this website. 

First, let’s have a refresher course on photosynthesis.


Leaves are nature’s food factories. Plants take water from the ground through their roots. They take a gas called carbon dioxide from the air. Plants use sunlight to turn water and carbon dioxide into glucose. Glucose is a kind of sugar. Plants use glucose as food for energy and as a building block for growing. The way plants turn water and carbon dioxide into sugar is called photosynthesis. That means ‘putting together with light.’ A chemical called chlorophyll helps make photosynthesis happen. Chlorophyll is what gives plants their green color.” 

How do leaves change colours?


As summer ends and autumn comes, the days get shorter and shorter. This is how the trees ‘know’ to begin getting ready for winter. During winter, there is not enough light or water for photosynthesis. The trees will rest, and live off the food they stored during the summer. They begin to shut down their food-making factories. The green chlorophyll disappears from the leaves.

As the bright green fades away, we begin to see yellow and orange colors. Small amounts of these colors have been in the leaves all along. We just can’t see them in the summer, because they are covered up by the green chlorophyll.


The bright reds and purples we see in leaves are made mostly in the fall. In some trees, like maples, glucose is trapped in the leaves after photosynthesis stops. Sunlight and the cool nights of autumn cause the leaves turn this glucose into a red color.


The brown color of trees like oaks is made from wastes left in the leaves.


It is the combination of all these things that make the beautiful colors we enjoy in the fall.”


Since we have shorter days now, it is actually the lack of sunlight that causes the leaves to lose their green colour.  And going back to the tree in the above photo, I guess that side is the one exposed to the cold the most so the leaves on that side are the ones changing colours first, wither and and then fall off the branches.  The other side is protected from the cold temperatures by the other trees and the house behind it.


Entry filed under: Autumn.

The other (ugly) side of Fall Autumn is a second spring

26 Comments Add your own

  • 1. Lazarus  |  October 5, 2006 at 12:04 am

    very informative. Thank God for the colors! Nature has its way of beautifying itself in different seasons.

  • 2. ladybug  |  October 5, 2006 at 12:57 am

    I find the colors of fall very beautiful. Too bad there are only 2 seasons here in the Philippines.

  • 3. sesame  |  October 5, 2006 at 1:48 am

    That’s interesting! The trees are alive!

  • 4. mmy-lei  |  October 5, 2006 at 2:49 am

    thanks for refreshing our minds regarding photosynthesis and chlorophyll.

  • 5. Kyels  |  October 5, 2006 at 2:59 am

    Yes, I like the colors of fall. They are nice.

    But well, I still have yet to experience the four seasons. And I wish I could be somewhere snowy right now. Heehee.


  • 6. melai  |  October 5, 2006 at 3:59 am

    wow review sa ecology ito 🙂 at sa natural science 🙂

  • 7. watson  |  October 5, 2006 at 5:33 am

    Niceheart, ang ganda naman. Thanks for sharing your fall fascination. At least parang galing na rin kami dyan 🙂

  • 8. Leah  |  October 5, 2006 at 10:07 am

    Yes, thanks for the great info.
    Fall is one of my favourite seasons. I love the colours and when leaves fall, the crunching sound of the leaves when you step on them is just wonderful. It will be nice to go for a nature walk on a sunny day.

  • 9. ipanema  |  October 5, 2006 at 1:35 pm

    It’s funny that sometimes I see trees here turning reddish – not many though- and I didn’t bother why. But there must be a reason somewhere. I like to see different colours of leaves, they’re a great contrast to the everlasting natural green.

  • 10. niceheart  |  October 5, 2006 at 11:03 pm

    I also think, Lazarus, that there is beauty in every season.

    Aren’t they pretty, Ladybug? Don’t feel too bad about having only 2 seasons. Winter here can be harsh. 😦

    Sesame, they are alive. They just hibernate in the winter. I remember my mother telling me that when she first experienced winter here, she thought that the trees died. 🙂

  • 11. niceheart  |  October 5, 2006 at 11:08 pm

    Mmy-lei and melai. It’s like being in first grade again, no? 🙂

    Kyels, glad you like the colours too. But be careful what you wish for. 🙂

    You’re welcome, watson. I sometimes feel like a kid when the seasons change here. 🙂

  • 12. niceheart  |  October 5, 2006 at 11:11 pm

    Hello, Leah. I also like that crunching sound when you step on the leaves.

    Leaves turn red there, too, Ipanema? I also love that contrast between the evergreens and the different coloured leaves. That’s why I include them in my photos.

  • 13. melai  |  October 6, 2006 at 12:00 am

    thanks po niceheart sa comment 🙂 … got a message earlier i pass the interview at may appointment na ko ng medical 🙂 ang saya ko .,.. now health ko naman ang kailangan kong ipagpray lol!! I don’t know yet kung makakapagsuot ako ng winter coat this year lol!! I just hope so 🙂

  • 14. aurea  |  October 6, 2006 at 11:25 am

    Maybe since one side of the tree is exposed to more sunlight, there’s more glucose there. According to the article, it’s the glucose that turns red – so this may be why the top of the tree changes color first. But I’m just speculating 🙂

  • 15. haze  |  October 6, 2006 at 12:39 pm

    Thanks for refreshing me on how chlorophyll & photosynthesis work ! It’s true that the color of fall is fascinating ! But the negative side of this is the falling flowers & pollen which make us susceptible with allergies 😦 . Nose & eyes irritation masama pag may kasamang fever.

  • 16. Abaniko  |  October 7, 2006 at 3:41 am

    Be glad you’re treated to some seasonal visual feast. Here, we generally have two colors for the leaves, green and bown. Boring, eh?

  • 17. Sidney  |  October 7, 2006 at 9:21 am

    Very informative post! I learned something new today !

  • 18. niceheart  |  October 7, 2006 at 11:01 pm

    Congrats, melai. And goodluck on the medical exam. 🙂

    Aurea, I think you are right in your speculations.

    That’s true, Haze. The pollens can trigger allergies in some people. But that usually happens in the Spring. I think it’s the cold weather that causes allergies in the Fall.

  • 19. niceheart  |  October 7, 2006 at 11:02 pm

    I don’t think it’s boring, Abaniko. There are lots of colourful and beautiful flowers there all year long.

    Thanks, Sidney.

  • 20. cruise  |  October 7, 2006 at 11:16 pm

    wow may natutunan ako dito, yun pala ang reason kung bakit nagbabago kulay ng mga dahon. meron pa rin kaunting halaman na di affected nito, bakit kaya?(tulad ng mga pines)

  • 21. zeroimpact  |  October 8, 2006 at 1:08 am

    Now I know something more… thanks
    The changing colours does provide us with a beauty that we never cease to grow bored of
    It’s just beautiful how life depicts it’s chapter and never fail

  • 22. bugsybee  |  October 8, 2006 at 7:13 am

    That was a good refreseher, niceheart! Complete with pictures too. How I wish learning was like this in my grade school days! Thanks a lot.

  • 23. Toe  |  October 8, 2006 at 8:32 am

    Beautiful pictures Niceheart! You have a very curious mind. Not only did you appreciate these beautiful colors, you also took time to find out the reason for these amazing changes.

  • 24. niceheart  |  October 8, 2006 at 11:00 pm

    Cruise, the pines have special leaves that are resistant to cold and moisture loss. I’ll write about this in a future post.

    Zeroimpact, the changing colours is the only exciting thing I enjoy with this season.

    Bugsybee, I wish that were too. Grade school kids here are always asked to collect leaves for their art and science projects.

    Thanks, Toe. I guess I am curious because I didn’t experience this growing up. 🙂

  • […] Dig deeper into the topic here […]

  • 26. shugen  |  April 29, 2010 at 8:38 pm

    woah..every single thing that happens to our surrounding really affects us,its good to know and appreciate this.


Leave a Reply

Fill in your details below or click an icon to log in:

WordPress.com Logo

You are commenting using your WordPress.com account. Log Out /  Change )

Google+ photo

You are commenting using your Google+ account. Log Out /  Change )

Twitter picture

You are commenting using your Twitter account. Log Out /  Change )

Facebook photo

You are commenting using your Facebook account. Log Out /  Change )


Connecting to %s

Trackback this post  |  Subscribe to the comments via RSS Feed

%d bloggers like this: