Wednesday, May 06, 2015

Home News Why leaves really fall off trees

Why leaves really fall off trees

Trees & Ornamentals

You think you know why leaves fall off trees. Well, you're wrong. It's not the wind. It's not the cold.

National Public Radio | December 7, 2009

You think you know why leaves fall off trees. Well, you're wrong. It's not the wind. It's not the cold. It's because trees use "scissors" to cut their leaves off.

We call this season the "fall" because all around us right now (if you live near leaf-dropping trees in a temporal zone), leaves are turning yellow and looking a little dry and crusty. So when a stiff breeze comes along, those leaves seem to "fall" off, thus justifying the name "fall."

Sounds reasonable, no?

But the truth is much more interesting.

According to Peter Raven, president of the Missouri Botanical Garden and a renowned botanist, the wind doesn't gently pull leaves off trees. Trees are more proactive than that. They throw their leaves off. Instead of calling this season "The Fall," if trees could talk they'd call this the "Get Off Me" season.

Here's why.

Around this time of year in the Northern Hemisphere, as the days grow shorter and colder, those changes trigger a hormone in leaf-dropping trees that sends a chemical message to every leaf that says, in essence, "Time to go! Let's part company!"

Once the message is received, says Raven, little cells appear at the place where the leaf stem meets the branch. They are called "abscission" cells. They have the same root as the word scissors, meaning they are designed, like scissors, to make a cut.

And within a few days or weeks, every leaf on these deciduous trees develops a thin bumpy line of cells that push the leaf, bit by bit, away from the stem. You can't see this without a microscope, but if you looked through one, you'd see those scissors cells lined right up.

Read more at NPR.org.

Top news

Get the most out of mulch

Keep your crew moving smoothly during application.

New turf and ornamental brand announced

Koch Turf & Ornamental will be dedicated to the golf, lawn care, ornamental and turf markets.

Volunteers take care of "Witness Trees"

The trees at Oak Ridge Cemetery were present 150 years ago at President Lincoln's funeral.

NALP board president named

Scott Jamieson took over the role on May 1.

Tips from the top: Dale Elkins

Dale Elkins talks about why it's important to keep your eye on the ball.

x