How Do Banyan Trees Work?

 These giant trees grow trunk-like roots down from their branches and can cover the area of city blocks. Learn more about banyan trees in this episode of BrainStuff, based on this article: https://science.howstuffworks.com/life/botany/understanding-roots-banyan-tree.htm

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Episode Transcript

Speaker 1 (00:01):
Welcome to Brainstuff, a production of iHeartRadio, Hey Brainstuff Lauren Vogelbam.
Here in Kolkata, the capital of the Indian state of
West Bengal, tourists flock to a botanical garden to see what,
at first glance, looks like an expansive forest. Branches of
green leaves create a canopy about the size of a

(00:24):
Manhattan city block. But the most interesting thing about this
collection of plant life is that it's not a collection
at all. It's one massive tree, known simply as the
Great Banyan tree, and all of those apparently distinct members
of a forest are actually one of about three thousand,
six hundred aerial roots that this single organism has put

(00:44):
down over its two hundred and fifty years of life.
If you're wondering how in the world one tree could
cover some fourteen thousand, five hundred square feet of space
that's about three hundred and fifty square meters, and grow
branches as high as eight feet that's twenty five meters
and survive over two and a half centuries, it's time

(01:05):
to get to know a special group of trees known
as banyans. Abanyons are part of the Picus or fig genus,
and their history is rooted unintended in South Asia. Originally
the name only referred to a single species, a Ficus bengalensis,
named for the Hindu merchants and traders who conducted their

(01:25):
business under the trees canopies. In these days, the name
can refer to a number of species that fall under
the not at all threatening sounding category of strangler figs.
This means the trees grow from seeds that land on
other trees, growing their own vines up and sending their
own roots down to smother their hosts. Before the article,

(01:48):
this episode is based on How Stuff Works. Spoke via
email with Aaron Alvarez and Bart Schitzman, both lectures in
the Environmental Horticulture department at the University of Florida. They
explained these plants all start life as a seed that
germinates on another tree, grows as a vine, dependent on
the tree for support, and eventually strangles its host tree,

(02:08):
subsuming its structure. Later, roots grow from outward extending branches
and reach the ground, becoming trunk like and expanding the
footprint of the tree, sometimes gaining it in the colloquial
name of a walking tree. While Kolkatta's Great Banyon is
by far the greatest of them all. A Banyons as

(02:29):
a species dominate size wise, at least in broadness. They're
the world's biggest trees in terms of the area they cover.
When it comes to overall volume, however, they lose to
the giant Sequoia. We've talked on the show before about
the two thousand year old tree named General Sherman living
in California's Sequoia National Park. That's about fifty two thousand,

(02:49):
five hundred cubic feet and volume or about one thousand,
five hundred cubic meters. The banyan is considered a particularly
meaningful tree in cultures around India and other parts of
the world, with rich historical and spiritual ties. In Hinduism,
the banyan is associated with the god of death, Yama,
and is often planted near crematoriums outside of villages, and

(03:13):
stories say that the god Krishna stood beneath the banyan
tree when he delivered the teachings of the Scripture. The
Bagavad Gida Hindu texts written over two thousand, five hundred
years ago, describe a cosmic world tree an upside down
growing banyan that has roots in heaven and extends new
growth from trunks and branches down toward earth to deliver blessings.

(03:35):
Over the centuries, the banyan tree took on significance as
a symbol of fertility, life, and resurrection. A word got
around about them, and the poet John Milton wrote about
Adam and Eve making their first clothes out of banyan
leaves in his epic Paradise Lost. The banyan has also
served as a source of medicine and food for centuries,
and the bark and roots are still used today to

(03:57):
treat a variety of maladies in Aurvedic medicine. When the
British invaded India, the tree was twisted to a newly
dark purpose, often used as gallows to execute rebels who
resisted their rule. When India gained independence, the people reclaimed
the banyan as well, making it their national tree. A

(04:18):
Banyans are native to and thrive in what's now India, Bangladesh,
and Pakistan, but these days variations of the majestic trees
can be found in other tropical regions, such as areas
of Florida. In some places, they've even become invasive. There's
also one famous species representative on the Hawaiian island of Maui,
the Lahina banyan tree, planted in eighteen seventy three and

(04:41):
presented to the sheriff in town by missionaries from India.
Now forty feet or twelve meters tall, the Lahina banyan
has a canopy circumference spanning a quarter mile that's about
four hundred meters. Today's banyans aren't just beautiful and symbolic.
The species also comes in handy for practical purposes. Alvarez

(05:03):
and Shutsmen said this ability of tiny picus roots to
become trunk like structures is used by the people of Megalaya,
India to create footbridges across streams that become raging rivers
during the monsoon season. They weave the tiny roots of
our well known rubber tree another Ficus together to cross
the streams. They enlarge and form sturdy structures that can

(05:25):
live five hundred years or more and do not get
washed away during the storms. However, although you may be
tempted to grow your very own great banyan tree now
that you know the unique magic of their aerial roots,
they need some pretty specific conditions. Alvarez and Shutsmen said
the best way to care for them is to give

(05:45):
them plenty of space and warm, wet, humid weather. So
most banyans don't make very good plants for regular home gardens.
A few species have adapted to indoor environments and can
be grown in bright in direct light with regular watering. However,
they are not as long long lived as their relatives
in the wild. Today's episode is based on the article

(06:08):
the mighty Banyan tree can walk and live for centuries
on how Stuffworks dot Com, written by Michelle Constantinofsky. Brain
Stuff is production of iHeartRadio in partnership with how Stuffworks
dot Com and is produced by Tyler Klang. Four more
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