How Big Can a Tree Grow?

There's actually a natural limit on how tall trees can grow -- but what about circumference? Or total mass? Learn more in this episode of BrainStuff, based on this article: https://science.howstuffworks.com/life/botany/tree-grow.htm

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Episode Transcript

Speaker 1 (00:01):
Welcome to Brainstuff, a production of iHeartRadio, Hey brain Stuff
Lorn Vogel bomb here. Back in two thousand and eight,
a study proposed that the maximum height for a Douglas Fir,
one of the world's tallest types of trees, is right
about at four hundred and fifty three feet. That's one
hundred and thirty eight meters. But why is there a

(00:24):
specific limit. Trees are nature's skyscrapers, but as it turns out,
nature has hemmed them in. That's because trees can only
physically pull water so far up their trunks. The transporters
in question are a type of dead cells called tray kids,
with deep pits that help move water from one long,

(00:45):
skinny cell to the next. The diameter of these all
important pits shrinks as you ascend into a tree's upper reaches,
complicating water transport. Eventually, the flow of water reaching the
leaves and branches near the top dwindles or stops entirely,
and the struggling sections experience drought stress and they become

(01:05):
dehydrated and die, establishing a de facto maximum height for
that tree. Researchers think these progressively narrowing pits actually help
trees survive. A height poses the problem of air bubbles.
The taller the tree, the more likely it will develop
a xylum embolism, which is when air bubbles get in

(01:26):
and block the passage of water through the xylum, which
is the tissue that makes up a tree's vascular system
and allows it to transport water and minerals from the
roots to the rest of the plant. A xylum embolism
is similar to a human air embolism, in which air
enters the bloodstream and causes potentially severe complications. The trachid's
chain shape near the top of the tree to try

(01:48):
to prevent such air bubbles and withstand the increased pressure
of water being pulled three hundred feet up in the air,
but that protection comes at a price less water and
as the ree searchers suggest, a cap on how tall
trees can grow. Another tree height study positive the maximum
height of all trees at four hundred and twenty six

(02:10):
and a half feet or one hundred and thirty meters.
The study examined coast redwoods, currently the world's tallest trees,
and based projection on factors like existing weather conditions, photosynthesis levels,
water flow, and carbon dioxide levels. And not surprising. Health
factors like water flow and photosynthesis decreased in the higher

(02:30):
portions of the massive trees, while unhealthy factors like carbon
dioxide increased, But ultimately, as with the furs, it all
comes down to xylum. These redwoods pull water up through
their trunks as other trees do, although they can absorb
some water from the fog that often surrounds them in
their native California and Oregon environments. Before attaining their maximum height,

(02:53):
they shoot up about ten inches that's twenty five centimeters
every year. But of course, tree size is more than
just height. The world's heaviest and most voluminous tree is
General Sherman, a giant sequoia, one of two types of
redwood found in California, the other being the taller, skinnier
Coast redwood that we just mentioned. General Sherman is estimated

(03:17):
to weigh over six thousand tons and encompass fifty two
thousand cubic feet that's about one thousand, five hundred cubic meters.
Located in California's Sequoia National Park, General Sherman is two
hundred and seventy five feet tall that's eighty four meters
but it's not the world's tallest tree. That honor belongs
to a coast redwood named Hyperion, which clocks in at

(03:39):
three hundred and seventy nine feet tall that's one hundred
and fifteen meters. A general Sherman also isn't the world's
widest tree. It has a trunk circumference of one hundred
and two feet or thirty one meters, but it's beat
out by l Arbol de Tule in Wajaca, Mexico, which
has a maximum circumference of one hundred and seventy eight
feet or fifty four meters. So there are different ways

(04:03):
of considering tree size, just as there are various ways
of considering what might be the world's largest living organism.
Some scientists consider massive reefs like Australia's Great Barrier reef,
to be giant singular organisms. There are also huge fungi
out there, such as a fungus discovered in Washington State
that spans one five hundred acres that's six hundred hectares.

(04:27):
But we are talking about trees here, and the world's
most massive living organism may be one group of quaking
aspen trees located in the mountains of Utah and nicknamed
Pando Latin for I spread. A Pando is considered one
organism because the trees in the group share an identical
genetic code and a common interconnected root system. The Pando

(04:51):
trees are basically clones of one another, and new trees
are made as stems spread out as far as one
hundred feet or thirty meters from the base of the
original tree and then periodically take root, creating new genetically identical,
interconnected trees. The process, known as vegetative reproduction, is also
how strawberries and many other plants reproduce. Pando is made

(05:15):
up of some forty seven thousand trees spread across one
hundred acres or forty hectors, and maybe up to eighty
thousand years old, but in testament to the massive size
of California's redwoods, this batch of forty seven thousand trees
weighs only about six thousand, six hundred tons, only a
little bit more in total than General Sherman. Today's episode

(05:41):
is based on the article how Tall can a Tree Grow?
On HowStuffWorks dot com, written by Jacob Silverman. Brainstuff is
production by Heart Radio in partnership with Hostiff Works dot
com and is produced by Tyler Klang. Four more podcasts
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