WEBVTT - BrainStuff Classics: Why Don't Evergreen Trees Lose Their Needles?

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<v Speaker 1>Welcome to Brainstuff, a production of iHeartRadio. Hey brain Stuff,

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<v Speaker 1>I'm Lauren vogele Bomb. And this is another classic from

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<v Speaker 1>our archives. This one details why evergreen trees like pines

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<v Speaker 1>and many other conifers get to keep their green leaves

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<v Speaker 1>year round, seemingly thumbing their nose at seasonal changes. Hey

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<v Speaker 1>brain stuff, lourenvogel Bomb. Here, evergreen trees seem to thrive

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<v Speaker 1>during the colder months, steadfastly holding on to their brightly colored,

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<v Speaker 1>needlelike leaves as temperatures plummet, bringing welcome color and contrast

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<v Speaker 1>to snowy landscapes. On the other hand, the wide and

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<v Speaker 1>flat leaves of their deciduous counterparts transform into brilliant shades

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<v Speaker 1>of red, orange and gold during the chilly and dry

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<v Speaker 1>days of fall and early winter, only to eventually shed

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<v Speaker 1>Their branches will remain barren until spring. So why are evergreens,

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<v Speaker 1>which include many, but not all coniferous trees such as pines, firs, junipers,

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<v Speaker 1>and spruces, is immune to seasonal leaf changes in shedding,

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<v Speaker 1>while species of deciduous trees like aspens, birch, cherry, oak,

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<v Speaker 1>and maple aren't. It mostly comes down to a little

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<v Speaker 1>thing you might have learned about in biology class called photosynthesis.

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<v Speaker 1>Both deciduous and evergreen trees use energy from the sun

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<v Speaker 1>and water from the ground to turn carbon dioxide in

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<v Speaker 1>the air into food. The difference is that shorter days

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<v Speaker 1>brings less sun during the fall and winter, and that

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<v Speaker 1>translates into less energy. So deciduous trees bearing broad, flat

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<v Speaker 1>leaves go dormant or into a sort of hibernation mode

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<v Speaker 1>and shed their leaves to help them conserve water and

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<v Speaker 1>stay alive until spring arrives and new leaves grow from

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<v Speaker 1>new buds. Evergreens, meanwhile, boast needles that are actually tightly

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<v Speaker 1>rolled leaves, and the low surface area of this shape

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<v Speaker 1>helps the needles conserve water throughout the fall and winter.

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<v Speaker 1>A waxy coating on the needles also helps keep water

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<v Speaker 1>from evaporating. Compared with broad delicate leaves, These dense waxy

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<v Speaker 1>needles resist cold and stay moist, which keeps them green

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<v Speaker 1>throughout the winter. But evergreens actually do shed their needles,

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<v Speaker 1>just not all at once. As needles age, they turn

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<v Speaker 1>yellow brown or a reddish tan and will fall from

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<v Speaker 1>the tree, but usually only a handful at a time.

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<v Speaker 1>The trees are constantly growing new needles so they can

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<v Speaker 1>stay green year round. Evergreens greater leaf longevity means they

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<v Speaker 1>can survive in environments that don't work for their deciduous cousins.

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<v Speaker 1>In fact, evergreens can be found on every continent except Antarctica.

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<v Speaker 1>The bottom line is that although those colorful deciduous trees

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<v Speaker 1>attract their share of seasonal leaf peepers, trees that stay

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<v Speaker 1>green year round add character to people's yards during the

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<v Speaker 1>fall and winter, offer shelter to birds and small animals

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<v Speaker 1>when the winter is cold, and many species are dense

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<v Speaker 1>enough to serve as windbreaks and privacy screens. Today's episode

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<v Speaker 1>is based on the article why evergreen trees don't shed

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<v Speaker 1>their needle like leaves on HowStuffWorks dot com, written by

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<v Speaker 1>Windy Bellman. Brain Stuff is production of iHeartRadio in partnership

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<v Speaker 1>with how stuffworks dot Com and is produced by Tyler Klang.

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<v Speaker 1>Four more podcasts my heart Radio, visit the iHeartRadio app,

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<v Speaker 1>Apple Podcasts, or wherever you listen to your favorite shows.