You have probably heard the story that grass is greener after a lightning storm, but is this really true?
How can lightning affect the color of your lawn? Let’s shed some light on this story.
The Story – Greener Grass After Lightning
The story goes something like this. The air contains 78% nitrogen and during lightning, some of this is converted to nitrogen dioxide, which dissolves in rain drops, and falls on your lawn. This extra nitrogen works just like a fertilizer; grass absorbs it and becomes greener.
Others say that the darker green color is created from wet grass sparkling in the sun. It’s all just an optical illusion.
Does Lightning Produce Nitrates?
We know that adding nitrate fertilizer to a lawn will make it greener and we know plants absorb nitrates. If lightning produces nitrates then it is quite possible the story is true.
The air does contain 78% nitrogen, and the energy of lightning is high enough to break apart the nitrogen gas creating reactive nitrogen molecules, which capture oxygen molecules to form nitrogen dioxide. This dissolves in rain droplets forming nitric acid, which is hydrogen nitrate.
The chemical part of the story is quite true.
How Green Does The Grass Get?
I had no problem finding lots of online posts about grass getting greener, but I did not find a single post that actually measured the color.
Without actual measurements or some kind of controls, we don’t really have any data confirming greener grass.
If you find some data, add a link in the comments.
Rain Washes Nitrates Away
A lightning storm may add nitrates to soil, but the rain washes nitrates that already exist in the soil to deeper levels, reducing the amount of nitrate in the soil. Extensive rain can reduce the nitrogen available to plants which would make grass less green.
Where Does The Rain Fall
This may seem like an odd question to ask, but meteorologists report that the rain falling during a lightning storm actually falls a great distance from the lightning itself.
So if there is lighting above you, the nitrogen produced does not fall on the grass below you, which means your grass does not get greener. For your grass to be affected, the lightning has to be far enough away so that by the time the rain reaches the ground, it is in your backyard. This distance depends very much on the prevailing winds.
It is almost impossible for a gardener to know that the rain falling on their lawn passed through a lightning strike, so how can they accurately report any color changes in their lawn and relate it back to lightning?
How Much Nitrogen Does Lightning Produce?
The science is clear, lighting produces nitrogen, but does it produce enough to make grass greener?
According to Dr. John Lauzon, an assistant professor in the Land Resource Science department at the University of Guelph, Ontario, receives about 20kg of N per hectare per year from the atmosphere. “That number is made up of two components, and roughly half of it is related to atmospheric losses of ammonia, with the other half related to the lightning strikes”. Lighting is adding 10 Kg/hectare/year or 1 g/m2. Let’s say there are 5 lightning storms a year. That is 2 Kg/hectare (1.8 lb/acre), or 0.2 g/sq m (0.006 oz/sq yd) of nitrogen being produced from one lightning storm.
According to Fertilizer for Dummies, a single application of fertilizer for lawns should be 4.9 g/sq m (0.15 oz/sq yd), or 20 times what the lightning storm adds.
Would 1/20 of the normal fertilizer you add to lawns make it green enough so that you could spot the difference? Not likely.
The Journal of Geophysics Research reports that lightning adds 100Tg/yr globally, which is 0.2 g/m2/yr – the same as the above number (Earth’s surface area is 5 E8 sq Km). NASA also calculated the amount of nitrogen produced by lightning and came up with 9 Tg/yr. If anything, the 1/20 value is on the high side.
The estimates for the amount of nitrogen from lightning range from 1 to 0.02 g/m2/y. The amount from a single rain event will be much lower.
Does Lightning Make Grass Greener?
Lightning does add nitrogen to the soil, but the amount is unlikely to show up as greener grass unless you live in an area with a very high number of lightning storms.
Why Do People Think The Grass is Greener?
It is quite possible that the grass is never greener. People just think it greens up because they have heard the story before. Knowing it gets greener convinces them it got greener.
It might look greener in full sunlight, after a rain.
The most likely scenario, assuming grass does green up, is that the water from the rain increases root activity, which in turn absorbs more nitrogen from the soil, causing greener leaves. If this were true, the grass would get greener after any heavy rain, even when lightning was not part of the storm. That is not what people report.
But let’s not forget that there seems to be no data supporting the idea that the grass is actually greener after a lightning storm. The whole story is most likely a fabrication of people’s imagination.
I’m a hay farmer. The nitrates in rain are absorbed into the plants through the stomata in leaves, not the nodules on the roots. The absorption is much more efficient requiring less total nitrogen for the same effect. Fertilizer you spread on your lawn is not 100% ortho, meaning it is not readily absorbable into the plant. It’s time released. Factor in runoff and you only get a fraction of the nitrogen you spread when you put it down. Nitrates in rain are immediately absorbed having a higher initial impact, but without as lasting an effect. Check out foliar feeding vs soil applied fertilizer.
Foliar fe3eding provides the nutrients faster, can can not provide nearly enough nitrogen for plants to grow. Most is absorbed by the roots.
https://www.gardenmyths.com/foliar-feeding-gardeners/
Someone should come up with a controlled experiment on that – but that said – there’s an observable difference between “after a heavy rain” and “after a thunderstorm” – so while it may not be the lighting, it’s *something*. My mother was a artist with an amazing eye for color, and she agreed. So I’ve checked it out every time I think of it, and close lightning/actual strikes make an observable difference. Also a bluer tone to the green. But I’m certainly not going to make a guess as to why.
Added data – my current lawn is pretty much sand – was just watching it for greening up (just came through a humdinger of an electrical storm) – and very little change – but it’s like grass in a desert. At my folks place when I was growing up – vastly better soil – I could see the difference. So maybe another data point there.
Hi Robert,
Thanks again for you valuable research.
I think what we have all noticed is that gardens look nicer after a decent rain coming at the end of a long summer drought. We recently had exactly that here along the east coast of Australia. It wasn’t just a storm and rain – the temperature dropped from unpleasantly hot to several weeks of pleasant temperatures – the humidity went from dry to moist. And the gardens improved dramatically with such favourable weather. I suppose lightning often comes with such weather.
It’s been over 60 years since my grade 6 class learned about the nitrogen cycle. As I recall, we were taught about nitrogen-fixing bacteria in the roots of legumes as well as ‘bonus nitrogen’ released during electrical storms. I remember our teacher saying that lawns and other plants would temporarily be greener afterwards. Something about ozone . . .
I don’t think I ever bothered to check if the world was greener after a thunderstorm in those days when I lived on the lower mainland of BC and storms were fairly frequent but now, where I live on the east coast of Vancouver Island, there are virtually no thunderstorms.
I miss the drama if nothing else.
I have read multiple articles stating the lightening would free up the Nitrogen in the air and it would fall to the ground with the rain drops to fertilize the grass.
That said, I will offer another explanation as to why the grass is greener after a storm. If you look around, everything seems more clear, more vibrant – not just the green grass, but all colors. As a photographer, I can tell you the best time to photograph anything outside is after a storm because the rain takes the dust out of the air. It’s a simple experiment to prove it to yourself, and these days, everyone has a camera on their cell phone. Take a few pics of flowers, your grass, even a person on a bright sunny day. Then, take those same shots, from the same vantage point, after a good rain. You will be amazed at the difference! Enjoy! 🙂
I love this stuff keep it up
I haven’t noticed any greener color but I have noticed that plants look a bit better after rain than if I just watered them with the hose. But then, my neighbor keeps dumping chemicals on the ground that goes into my well water and messes with my plants’ health and mine too. 🙁
I read somewhere that there is hydrogen peroxide in rain so could that also help the plants with extra oxygen?
Rain does contain hydrogen peroxide, but it is unlikely to give plants extra oxygen.
Elements in the soil over time become less available for the grass to use. A bolt of lightning is a high charge of positive and negative electrons, when it strikes the ground it cause a magnetic effect that seperates the elements that are locking together making them more available for the plant to use. *This could be complete bs, but it’s my theory.
Maybe its ozone? Or the thunder and lightening helps the rain wash more dust off leaves and things more efficiently. Just some crazy wild guesses. The air does smell cleaner and fresh after a good T storm.
Then there is the myth that the grass is greener on the other side of the fence. But how is “greener” measured? And what causes the extra nitrogen needed to always be on the other side of the fence? Lightning maybe? But why does the Lightning always strike on the other side of the fence? Man, gardening is a complex subject. Thank you for your myth busting posts 😉