Tuesday, April 21, 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

New equipment and facility for Caterpillar

The products were on display at the company’s newest production facility.

H-2B receives extension

The Department of Labor will continue processing applications through May 15.

Wheelchair-bound man receives new snow blower

Ariens replaced Kellermeier's older model after a photo of him went viral on Facebook.

Fun facts about natural grass lawns

For National Lawn Care Month, heighten your customers' awareness of the benefits of natural grass.

Project EverGreen renovates Georgia park

The "Healthy Turf. Healthy Kids." project enhanced the park's entranceway.

x