WTF Fun Fact 12978 – How Does Temperature Affect the Color of Leaves?

Have you noticed that autumn looks a bit different every year? Sometimes the leaves fall early. Other times they’re on the trees much longer to give a full display of color. A lot of this has to do with the temperature outside. But how does temperature affect the color of leaves?

The temperature of fall and its effect on leaves

As the nights get cooler in the northern hemisphere in September and October, we begin to see the trees change. If you’re lucky enough to live around a mixture of trees, you’ll begin to see bright red, orange, and yellow leaves appear.

Without as much daily sunlight, trees don’t go through as much photosynthesis. This is aprocess that produces sugars, which trees use as energy to grow and flower.

A reduction in photosynthesis leads to a reduction in chlorophyll as well, which is the pigment that makes leaves green. As they lose chlorophyll, they lose their green color and prepare to shed for the winter so trees can conserve their energy inside the branches and bark.

How does temperature affect the color of leaves?

But that still doesn’t explain the role of temperature.

The weather leading up to shorter days is actually quite important when it comes to determining how fall plays out for leaves .

We know that a reduction in chlorophyll leads to leaves being less green, but what makes some seasons produce more vibrant red leaves than others? Why does a tree turn bright orange one year and only a dull copper the next year?

Well, it turns out that the pigments that begin to show up once chlorophyll is reduced are dependent on both temperature and moisture conditions right before days start getting shorter. For example, some weather conditions make a leaf turn red early. It also helps it stay on the tree longer, so it goes through its full range of colors before falling off.

The role of weather in fall leaf displays

According to scientists at Michigan State (cited below), lots of warm days and cool nights narrow the veins in leaves. This helps trap the sugars made during photosynthesis in those leaves. When this happens, the sugars produce more vivid pigments.

“The most brilliant leaf displays follow a period of warm days filled with sunshine and cool nights. During this weather cycle, leaves produce an abundance of sugars during the sunny days. The cooler nights and gradual narrowing of leaf veins in the fall, means that a majority of the sugars produced are trapped in the leaf. An abundance of sugar and light in the leaf lead to the production of vivid anthocyanin pigments, which produce red, purple and crimson colors. Yellow and gold leaf colors are produced by carotenoid pigments, which are ever-present in the leaves and are therefore less dependent on the aforementioned conditions.”

Other factors in fall leaves

“Soil moisture also plays a role in the timing and brilliance of leaf color. The best displays are produced when the soil has been adequately moist throughout the year coupled with the aforementioned late summer weather. A late spring, or severe summer drought can delay the onset of color. A warm period during the fall can also decrease the intensity of fall colors by triggering early leaf drop before the colors have had a chance to develop.”

Finally, MSU explains that other factors can play a role in individual trees:

“Trees on the edge of low-lying areas, where cooler air collects at night, often display colors sooner than trees in an upland forested setting. Trees that are diseased or in decline may also display fall colors earlier than their healthy neighbors.

And that’s why no two autumns will ever look the same.  WTF fun facts

Source: “How weather affects fall colors” — Michigan State University Extension

WTF Fun Fact 12964 – Our Obsession With Pumpkins

Pumpking beer, pumpkin lattes, pumpkin cookies, pumpkin-spiced…you name it. Our obsession with pumpkins knows no bounds.

Even if you hate the taste of pumpkins, you might still be soothed by the sight of them. And there’s a reason for that.

What’s with our obsession with pumpkins?

Most pumpkin-flavored things don’t really taste like pumpkin or even contain pumpkin – in fact, most are made with a different type of squash altogether. We’re mostly in it for the spices.

Still, there’s a reason we market everything as “pumpkin flavored” – and it’s all about nostalgia.

According to NPR (cited below), a professor of American Studies at St. Louis University named Cindy Ott wrote a book titled Pumpkin: The Curious History of an American Icon in which she describes why we’re so drawn to the round, orange gourds.

It’s a vegetable that represents this idyllic farm life, and the best sort of moral virtue. And Americans have become attached to that,” she said.

“‘The rehab of pumpkin’s popularity began when 19th century Americans began to move away from rural life and into the city,’ Ott says. ‘People became stressed about… moving into the office and off the farms, and [the pumpkin] starts to appear in poems and in paintings,’ she says. ‘We’re celebrating the nostalgia for this old-fashioned, rural way of life that no one ever really wanted to stay on, but everyone’s always been romantic about.'”

Recycling pumpkin-flavored ideas

Did you know pumpkin beer isn’t a new phenomenon? Pumpkins were once the food of pure desperation.

NPR explains that “…pumpkin beers and pumpkin breads have been produced since colonial times, Ott says that they weren’t always the specialty foods that they are today. ‘Pumpkin beer was used when there was no barley. [If] there was no wheat for bread, they used pumpkin [for] bread,'”

If anyone mocks you for your pumpkin-flavored obsession, just tell them you’re helping the economy.

“Big corporations advertise many pumpkin-themed products, but due to their limited seasonal availability, many fresh pumpkins sold every fall still come from local family farms,” Ott told NPR. “And that’s actually helping to rejuvenate those farms.”  WTF fun facts

Source: “Why Americans Go Crazy For Pumpkin And Pumpkin-Flavored Stuff” — NPR