Speaker 1: Welcome to brain Stuff production of iHeart Radio, Hey brain
Speaker 1: Stuff Lauren vogebam here. Evergreen trees seem to thrive during
Speaker 1: the colder months, steadfastly holding onto their brightly colored, needle
Speaker 1: like leaves as temperatures plummet, bringing welcome color and contrast
Speaker 1: to snowy landscapes. On the other hand, the wide and
Speaker 1: flat leaves of their deciduous counterparts transformed into brilliant shades
Speaker 1: of red, orange and gold during the chili and dry
Speaker 1: days of fall and early winter, only to eventually shed
Speaker 1: Their branches will remain barren until spring. So why are evergreens,
Speaker 1: which include many, but not all, conniferous trees such as pines, furs, junipers,
Speaker 1: and spruces immune to seasonal leaf changes in shedding, while
Speaker 1: species of deciduous trees like aspens, birch, cherry, oak, and
Speaker 1: maple aren't. It mostly comes down to a little thing
Speaker 1: you might have learned about in biology class called photosynthesis.
Speaker 1: Both deciduous and evergreen trees use energy from the sun
Speaker 1: and water from the ground to turn carbon dioxide in
Speaker 1: the air into food. The difference is that shorter days
Speaker 1: brings less sun during the fall and winter, and that
Speaker 1: translates into less energy, so deciduous trees bearing broad flat
Speaker 1: leaves go dormant or into a sort of hibernation mode,
Speaker 1: and shed their leaves to help them conserve water and
Speaker 1: stay alive until spring arrives and new leaves grow from
Speaker 1: new buds. Evergreens, meanwhile, boast needles that are actually tightly
Speaker 1: rolled leaves, and the low surface area of this shape
Speaker 1: helps the needles conserve water throughout the fallen winter. A
Speaker 1: waxy coating on the needles also helps keep water from
Speaker 1: evaporating compared with broad, delicate leaves. These dense, waxy needles
Speaker 1: resist cold and stay moist, which keeps them green throughout
Speaker 1: the winter. But evergreens actually do shed their needles, just
Speaker 1: not all at once. As needles age, they turn yellow
Speaker 1: brown or a reddish tan and will fall from the tree,
Speaker 1: but usually only a handful at a time. The trees
Speaker 1: are constantly growing new needles, so they can stay green
Speaker 1: year round. Evergreens greater leaf longevity means they can survive
Speaker 1: in environments that don't work for their deciduous cousins. In fact,
Speaker 1: evergreens can be found on every continent except Antarctica. The
Speaker 1: bottom line is that Although those colorful deciduous trees attract
Speaker 1: their share of seasonal leaf peepers, trees that stay green
Speaker 1: year round add character to people's yards during the fall
Speaker 1: and winter, offer shelter to birds and small animals when
Speaker 1: the winter is cold, and many species are dense enough
Speaker 1: to serve as wind breaks and privacy screens. Today's episode
Speaker 1: was written by Windy Bowman and produced by Tyler Clang.
Speaker 1: The brain Stuff is production of iHeart Radious How Stuff Works.
Speaker 1: For more in this and lots of other evergreen topics,
Speaker 1: visit our home planet, how stuff Works dot com. And
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