Autumn Enigma

December 1, 2015 6:47 AM

Why are autumn leaves mostly yellow in Europe and red in North America? The colour of a British wood in autumn is predominantly yellow. There are relatively few European trees which have red leaves in the autumn....Autumn is much redder in North America and east Asia than it is in northern Europe, and this can’t be explained by temperature differences alone.
posted by caddis (25 comments total)

This is one of those better kind of mysteries. I had spent a fall in England and hardly noticed the absence of red. Incidentally, I vividly remember the final fight scene in The House of Flying Daggers, set in China, and thought, "That could be a field somewhere in North America by the way the trees look."
posted by Atreides at 7:20 AM on December 1, 2015 [1 favorite]

I thought it was caused by a difference in the minerals in the soil. The soil in New England has lots of iron in it (relatively speaking) and this gets absorbed by the trees and moves up to the leaves.

Also, the last scene of House of Flying Daggers was filmed in Ukraine.
posted by Chocolate Pickle at 7:29 AM on December 1, 2015 [9 favorites]

Predominantly red in the American northeast. In aspen country in the Rockies, it;s yellow.
posted by ocschwar at 7:30 AM on December 1, 2015 [3 favorites]

In terms of climate, the American Northeast has a lot in common with Manchuria, Korea and Japan. It's on the leeward side of a large continent, so it gets the weather extremes. Europe and the Pacific Northwest get the temperature moderation from being on the windward side. (Albeit thanks to the Rockies, the moderation doesn't last very far inland.)

Note the Northeast's Anishinabe name, Wabanaki, is "land of the rising sun," and both regions are full of maples.
posted by ocschwar at 7:40 AM on December 1, 2015 [2 favorites]

I'm in Chicago, I see a lot more yellow and orange than red.
posted by JoeZydeco at 7:43 AM on December 1, 2015 [4 favorites]

Getting a lot of red and oranges along w/ yellows down here in north TX. It's very pretty. But a lot of those red/orange trees are not native to our state, pretty sure some of them were imported because of their pretty coloring. The author also says some species imported to UK from US have red coloring. So I don't think it's the soil.
posted by emjaybee at 7:50 AM on December 1, 2015

In Wisconsin, our reds seem to be mostly maples and sumac, but I feel like the red/yellow ratio is about 50/50. There's a lot of trees I'm not yet familiar enough with to identify.
posted by LionIndex at 7:57 AM on December 1, 2015 [1 favorite]

Autumn is the reason why I miss living in a temperate climate so much.
posted by destrius at 7:58 AM on December 1, 2015 [1 favorite]

It feels like the trees in the northeast are getting yellower.
posted by jeather at 8:08 AM on December 1, 2015 [1 favorite]

One of the themes of our developing awareness of forest ecology is how things are linked - trees are part of huge networks mediated by intermeshing roots, subterranean fungi and who knows what else communicating through chemical signals. It wouldn't surprise me if one of the evolutionary drivers behind the different pigmentations was how the leaves were re-integrated into the substrate after they fell, whether it's to preserve certain chemicals for use outside the tree, adjust the timing of the fall, or (as the article says) modulate the effect of leaf-eating insects or other things. Or whether it's a harmless atavism.

I miss living among trees, though. Autumn woodlands are psychedelic, in the best way.

(Actually, woodlands are in any season, but with different nuances.)
posted by Devonian at 8:12 AM on December 1, 2015 [4 favorites]

I thought it was caused by a difference in the minerals in the soil. The soil in New England has lots of iron in it (relatively speaking) and this gets absorbed by the trees and moves up to the leaves.

No, because it varies by tree species. I mean, there's also some variation from tree to tree and year to year (I can never *quite* predict the conditions, but a rainy summer seems to make for drab fall colors. Stressed trees, those near buildings for example, tend to turn early and spectacularly.), but maples and sumac will always have red(dish) leaves and the birches and aspens will always be yellow.

I'll be back after reading the article, but the short answer is almost certainly "evolution".
posted by maryr at 8:23 AM on December 1, 2015 [4 favorites]

Also, the last scene of House of Flying Daggers was filmed in Ukraine.

Boom!
posted by Atreides at 8:38 AM on December 1, 2015

huh, so.... is there even a mystery here? Or did the writer just notice that two places they've visited have different colors of trees?

(also, the answer is, as always - "Maybe evolution had something to do with it??")
posted by rebent at 9:40 AM on December 1, 2015 [1 favorite]

Well, I've got a tree that turns red in the fall. It's a cultivar of Norwegian maple.

Pretty sure that's all there is to it: Yes, there are a few successful native species that are naturally red, but mostly we import stuff from Europe and redden it through selective breeding because that's what sells here.
posted by Sys Rq at 10:15 AM on December 1, 2015

Some science
posted by caddis at 10:49 AM on December 1, 2015

According to this page, carotenoids give rise to the yellow and orange colors and are present throughout the Summer, whereas anthocyanins are responsible for the reds but are produced in the Fall, most strongly in response to certain conditions:

Perhaps you've noticed that in some years, the red fall colors seem brighter and more spectacular than in other years. The temperature and cloud cover can make a big difference in a tree's red colors from year to year.

When a number of warm, sunny autumn days and cool but not freezing nights come one after the other, it's going to be a good year for reds. In the daytime, the leaves can produce lots of sugar, but the cool night temperatures prevent the sugar sap from flowing through the leaf veins and down into the branches and trunk. Anthocyanins to the rescue! Researchers have found out that anthocyanins are produced as a form of protection. They allow the plant to recover nutrients in the leaves before they fall off. This helps make sure that the tree will be ready for the next growing season. Anthocyanins give leaves their bright, brilliant shades of red, purple and crimson.

And if we look at a map of the Gulf Stream, it's clear that Fall conditions of sunny days followed by nights cool enough to make it difficult for sap to flow are far more likely in New England than they are in Europe.

So I would say the answer to the enigma lies in the existence of the Gulf Stream.
posted by jamjam at 11:17 AM on December 1, 2015 [3 favorites]

There are relatively few European trees which have red leaves in the autumn

fraula is not in teh europes?!
red leaves in France
orange and yellow leaves in Paris
red-orange leaves in front of Gothic church
red-orange-yellow-green (my favorite photo from this autumn)
HI I CAN HAZ RED LEAVES
posted by fraula at 11:47 AM on December 1, 2015 [2 favorites]

Well, I've got a tree that turns red in the fall. It's a cultivar of Norwegian maple.

Pretty sure that's all there is to it: Yes, there are a few successful native species that are naturally red, but mostly we import stuff from Europe and redden it through selective breeding because that's what sells here.

I don't think that's it. The sugar maple and red maple are two of the most common species in the U.S. and both are native to North America. Silver maples are also quite common. It does seem that human-driven changes to the ecosystem are making maples even more common, but that's not about taking a tree from Europe and breeding the heck out of it.

I've lived all my life in either Vermont or the upper Midwest (mostly Minnesota, but a little Iowa, Michigan, and even Wisconsin) and my visits to Europe have been in other seasons so it just never occurred to me that there would be a place that had Fall but without so many red and orange leaves. I like articles like this one that remind me that other places in the world are different in ways I hadn't contemplated.
posted by Area Man at 11:48 AM on December 1, 2015 [2 favorites]

Vermont maple leaves.
posted by maryr at 12:22 PM on December 1, 2015

In Pacific NW North America, the native trees are a lot more yellow than red, although shrubby plants can provide some potent red.
posted by polecat at 2:08 PM on December 1, 2015

In Pacific NW North America, the native trees are a lot more yellow than red, although shrubby plants can provide some potent red.

I'm always looking for reasons to hate Oregon so this is welcome news.
posted by Area Man at 2:12 PM on December 1, 2015 [1 favorite]

That article is not very scientific. I'll start out as unconvinced that there are continental differences in leaf color. Then I'll point out that the red and yellow colors in leaves are always there, but masked when chlorophyll is present. They are part of photosynthesis, so while they are undoubtedly selected for, there's no point in randomly speculating about herbivory. Right now my front yard Liquidambar is green, yellow, orange and red. It's gorgeous.
posted by acrasis at 3:49 PM on December 1, 2015

I have heard an explanation of this phenomenon that relates it to the geography of mountain ranges and their interaction with glaciation. But it sounds like this is less than fully settled. I've just spent my first fall in England after living my whole life in the USA, and I definitely noticed the lack of vivid red colors.

red and yellow colors in leaves are always there...did you read the article? It specifically addresses this point; red pigments are not present in the leaf during the spring/summer but rather are produced in the autumn.
posted by dendrochronologizer at 6:47 PM on December 1, 2015

From what I can remember from college ecology courses, trees do produce new red and yellow pigments during the fall as well as break down and remove leaf components before they drop.
posted by 3urypteris at 6:50 PM on December 1, 2015

Wait, it's not as though entire species have gone extinct in Europe in ways they haven't here.
posted by persona au gratin at 7:15 PM on December 1, 2015