# Autumn tree colors & sunlight **URL:** \ **Category:** Factual Questions\ **Created:** [March 29, 2023, 2:55am UTC](https://boards.straightdope.com/t/autumn-tree-colors-sunlight/981817 "2023-03-29T02:55:05Z")\ **Posts on this page:** 10\ **Page:** 1
**Author:** ![purplehorseshoe](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/purplehorseshoe/32/2996_2.png) [@purplehorseshoe](https://boards.straightdope.com/u/purplehorseshoe)\ **Post date:** [March 29, 2023, 2:55am UTC](https://boards.straightdope.com/t/autumn-tree-colors-sunlight/981817/1 "2023-03-29T02:55:05Z")
When trees (esp. those that show spectacular autumn colors, such as maples) get sunlight from predominantly one side, does the “sunny” side stay greener longer, or is that the side that loses chlorophyll and shows red/orange/yellow first? (I’m doing some artwork featuring a blazing autumn maple, and since I’m trying to show the “sideways” autumn light we get here in Michigan, I wanted to make it as botanically accurate as possible.) Many of our autumn trees have a “tie-dye” effect, with various colors on the same tree, which I assume must be the result of varying light - shade from other trees, the sun “hiding” behind a house, etc. Any & all info related to the topic highly welcomed! ---
**Author:** ![gnoitall](https://avatars.discourse-cdn.com/v4/letter/g/bb73d2/32.png) [@gnoitall](https://boards.straightdope.com/u/gnoitall)\ **Post date:** [March 29, 2023, 3:36am UTC](https://boards.straightdope.com/t/autumn-tree-colors-sunlight/981817/2 "2023-03-29T03:36:36Z")
Color change is a full-tree phenomenon. The changes are internal, and the entire tree undergoes it all at the same time. It’s triggered by shortening day length. [https://www.fs.usda.gov/visit/fall-colors/science-of-fall-colors](https://www.fs.usda.gov/visit/fall-colors/science-of-fall-colors) **Length of Night** > **In early autumn, in response to the shortening days and declining intensity of sunlight,** leaves begin the processes leading up to their fall. The veins that carry fluids into and out of the leaf gradually close off as a layer of cells forms at the base of each leaf. These clogged veins trap sugars in the leaf and promote production of anthocyanin. Once this separation layer is complete and the connecting tissues are sealed off, the leaf is ready to fall. ---
**Author:** ![solost](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/solost/32/11776_2.png) [@solost](https://boards.straightdope.com/u/solost)\ **Post date:** [March 29, 2023, 1:13pm UTC](https://boards.straightdope.com/t/autumn-tree-colors-sunlight/981817/3 "2023-03-29T13:13:31Z")
> [@gnoitall](#): > > It’s triggered by shortening day length. > > [https://www.fs.usda.gov/visit/fall-colors/science-of-fall-colors](https://www.fs.usda.gov/visit/fall-colors/science-of-fall-colors) Also by weather, as your post states. Temperature and moisture level, specifically. Anecdotally, I seem to have noticed the trees here in SE Michigan routinely turning color later in the season than in past years due to longer warm seasons caused by global warming. @purplehorseshoe , would love to see your artwork when it’s finished. Post it here if you like, or PM me a pic! ---
**Author:** ![Jasmine](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/jasmine/32/2964_2.png) [@Jasmine](https://boards.straightdope.com/u/Jasmine)\ **Post date:** [March 29, 2023, 2:00pm UTC](https://boards.straightdope.com/t/autumn-tree-colors-sunlight/981817/4 "2023-03-29T14:00:59Z")
> [@gnoitall](#): > > Color change is a full-tree phenomenon. The changes are internal, and the entire tree undergoes it all at the same time. As a native of the Berkshire Hills in western MA, I can visually attest to that. ---
**Author:** ![Shoeless](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/shoeless/32/7099_2.png) [@Shoeless](https://boards.straightdope.com/u/Shoeless)\ **Post date:** [March 29, 2023, 4:58pm UTC](https://boards.straightdope.com/t/autumn-tree-colors-sunlight/981817/5 "2023-03-29T16:58:19Z")
> [@gnoitall](#): > > Color change is a full-tree phenomenon. The changes are internal, and the entire tree undergoes it all at the same time. Huh. I definitely remember walking around the neighborhood in the fall and seeing trees that had turned red or yellow on one side and were still green on the other. Also there were trees that lost all the leaves on one side but not the other. It seemed to be an east-west thing, but I don’t remember which sides were which. I assumed it had to do with which side was getting more sun during the day. I’ll have to remember this thread in the fall and see if I can get some pictures to post. ---
**Author:** ![purplehorseshoe](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/purplehorseshoe/32/2996_2.png) [@purplehorseshoe](https://boards.straightdope.com/u/purplehorseshoe)\ **Post date:** [March 29, 2023, 6:54pm UTC](https://boards.straightdope.com/t/autumn-tree-colors-sunlight/981817/6 "2023-03-29T18:54:53Z")
> [@Shoeless](#): > > I definitely remember walking around the neighborhood in the fall and seeing trees that had turned red or yellow on one side and were still green on the other. Also there were trees that lost all the leaves on one side but not the other. It seemed to be an east-west thing, but I don’t remember which sides were which. This is precisely what I’m asking about. Currently scrolling through 1,000s of cat pictures on my phone to see if I can find an example. ---
**Author:** ![purplehorseshoe](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/purplehorseshoe/32/2996_2.png) [@purplehorseshoe](https://boards.straightdope.com/u/purplehorseshoe)\ **Post date:** [March 29, 2023, 6:59pm UTC](https://boards.straightdope.com/t/autumn-tree-colors-sunlight/981817/7 "2023-03-29T18:59:33Z")
Gave up, too many kitties, but here’s some professional photos (watermarked) > **[Multi-colored autumn leaves on a Bradford Pear tree Stock Photo - Alamy](https://www.alamy.com/stock-photo-multi-colored-autumn-leaves-on-a-bradford-pear-tree-117338811.html)** > > Download this stock image: Multi-colored autumn leaves on a Bradford Pear tree. - GPW6RR from Alamy's library of millions of high resolution stock photos, illustrations and vectors. … and the banner photo for this page: > **[Top 10 Trees with colourful Autumn foliage at the Irish National Stud](https://irishnationalstud.ie/top-10-trees-with-colourful-autumn-foliage-here-on-the-farm-gardens/)** > > Over the coming weeks deciduous trees across the grounds here at the Irish National Stud will offer a final touch of drama to the gardens, as their leaves turn magnificent shades of golden yellow, orange, and red, before falling. I have compiled the... ---
**Author:** ![Spiderman](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/spiderman/32/230_2.png) [@Spiderman](https://boards.straightdope.com/u/Spiderman)\ **Post date:** [March 29, 2023, 7:43pm UTC](https://boards.straightdope.com/t/autumn-tree-colors-sunlight/981817/8 "2023-03-29T19:43:29Z")
> [@purplehorseshoe](#): > > Currently scrolling through 1,000s of cat pictures on my phone to see if I can find an example. You’re wasting your time; cats don’t change colors in Fall. ---
**Author:** ![Chronos](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/chronos/32/134_2.png) [@Chronos](https://boards.straightdope.com/u/Chronos)\ **Post date:** [March 29, 2023, 9:53pm UTC](https://boards.straightdope.com/t/autumn-tree-colors-sunlight/981817/9 "2023-03-29T21:53:37Z")
Some buns do, though. And leaves falling off one side before the other could easily be explained by differences in wind. If all of the leaf-stems are equally weakened, but there’s more wind on one side than the other, then it might be enough to pull off the leaves only on that side. ---
**Author:** ![dtilque](https://avatars.discourse-cdn.com/v4/letter/d/d6d6ee/32.png) [@dtilque](https://boards.straightdope.com/u/dtilque)\ **Post date:** [March 29, 2023, 10:08pm UTC](https://boards.straightdope.com/t/autumn-tree-colors-sunlight/981817/10 "2023-03-29T22:08:03Z")
As someone posted upthread, temperature and moisture influence how fast the fall colors form in the leaves. The local environment of the tree may cause one side of the tree to be warmer or more moist than the other side. Also, human produced lighting can have the same effect. I once had an office with a view of a row of trees along the side of the parking lot and was also partially alongside the building next door. For most of the trees, the leaves turned brown and fell off every fall. But one section of one tree stayed green the entire winter. This puzzled me until I realized that there was a bright light on the side of that building right next to that section of the tree.