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Why you should be seeing red if you want to understand your yard’s health

Paul Cappiello Ph.D.

Paul Cappiello Ph.D.

Yew Dell Botanical Gardens Executive Director

It’s finally June…

We slogged through the grays of winter. The visual cacophony of spring has come and gone. We’re not yet in the Dog Days. It’s a magical time in Kentucky and a good time to do a bit of homage paying to all that is green in the garden.

Growing up in suburban New York City we were surrounded by woods – mostly big old beech trees and giant oaks – and we had a large yard that was about half lawn and half garden. Being the oldest boy in the Cappiello clan meant that mowing the lawn was on my weekly chore list. And with my siblings I also spent countless hours pulling up sod strips to make way for new gardens. 

Back then, whether I was walking among the beech trees, pushing the old Craftsman mower over the lawn or yanking strips of turf from the ground I would often pass the time by imagining what was going on in all those green leaves. I’d imagine that one day I’d peer deeply into a leaf and it would magically spell out all the answers right then and there. Little did I know then that it would take a lifetime of peering deeply into leaves and after 60 years I’d still have a long list of questions.

But what I lack for answers today (because the deeper you look the more questions you find) doesn’t by any means dampen my endless wonder and appreciation for that ubiquitous green matter that quite frankly is responsible for our very existence. 

Green... It’s a funny thing right at the outset.

Ask anyone to identify the part of the visible light spectrum that is most important for sustaining life on earth – and most of us would quickly respond, “green!” But of course if you paid any attention at all to your freshman biology class you’ll know that our much favored green is actually the least useful color in the world’s ecological rainbow. Leaves look green because that’s the light wavelength that is mostly reflected back at our eyes! Indeed, the GREEN movement, if we really think about it, should actually be the RED movement – red being a far more important color of light when it comes to making and keeping our planet habitable by living and breathing organisms. (Of course I’m guessing any grassroots movement to promote a Reddening of America would likely go over like a lead balloon on an icy cold day!) 

Something like 2.7 billion years ago our planet was completely uninhabitable – oxygen, at least in a breathable form, was completely absent from our atmosphere (ok, there’s some evidence out there that this happened about a billion years earlier but we won’t get into that…) But the arrival of blue-green algae – the first significant photosynthesizing organisms – changed all that. Their supercharged photosynthetic apparatus sucked carbon dioxide out of the early atmosphere and pumped out oxygen gas. It took a while… and a few gazillion little algae engines… but the oxygen in the atmosphere gradually rose to a level that could support larger and more complex lifeforms. Without the photosynthesis going on in those little algae, we wouldn’t be here to scalp the lawn, volcano mulch the trees and otherwise make mayhem with the planet…

But here’s the question. What exactly is going on in those green leaves? While the answer is quite complex in the details, in summary it’s elegantly simple. Here’s the process…

1- Absorb Sun’s Energy

Chlorophyll (the “green” pigment in most leaves) and other pigments absorb the sun’s energy and use it to push electrons to a high energy state

2- Split Water Molecules

The high energy electrons work in a system that splits water molecules and in turn release the oxygen that is then available for us to breathe

3- Store Chemical Energy

Two molecules (ATP and NADPH) are formed and act somewhat like batteries, storing the energy released from the splitting of the water molecules.

4- Make Sugars

Finally, the energy stored in both ATP and NADPH is used to combine carbon atoms (from the carbon dioxide plants absorb) into sugars that we eat with pancakes and stir into our coffee. Oh, and the sugars can also be linked into starch and cellulose structures that are essential to plant development.

There. Now you’re ready for Jeopardy! 

Now at this point I could go into the quantum mechanics of the whole photosynthesis thing but I’d have to consult with my physics research department and last I checked he and his fiancé were driving across the Mohave Desert and either sun spots or the di-lithium crystals in the Nevada hills were interfering with cell service. So my simplified version will have to suffice for now… 

Or I suppose you could go out for a walk and look at the leaves. It’s always worked for me…

This article was originally submitted to the Courier Journal on June 8, 2022.

About the Author

Blurb about Paul here.

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