Does microwaved water kill plants?

“I saw a picture of a plant having grown better when watered with purified water vs. microwaved water. Is this real?”

The myth of microwaved waters effect on plants has been circulating for quite some time. The picture (apparently) came from a child who investigated the effects of microwaved water on plants for a science fair – which should ring the ol’ sceptical alarm bells.Construction Plant by Taz-Voll, on Flickr

Let’s start with what is true about this debate. Purified water or distilled water is better for plants (compared to tap water) as it removes the heavy metals, pollutants, chlorine and fluoride which affect the pH level of the soil. It’s a double edged sword because it rids the water of minerals necessary for a healthy and strong plant. So green thumbs worldwide recommend using distilled water with added fertiliser.  However, if your plant is an outdoor dweller then none of this information applies to you – rain knows how to do its job.

Right, let’s get down to the fun, sceptical side of science.  A lot of online science bloggers have investigated whether microwaved water does kill plants – some even believe that it does! One problem with drawing conclusions from a picture posted online is how can we know what they claim the picture to depict is actually true?  Whoever put the picture up could have had two plants and only watered one. We can go even further with our scepticism: if you only use two plants in an experiment, how can you draw any conclusions? What if the plant watered with microwaved water grew better?

But before I leave you with your answer, let me quickly explain why so many self-respecting scientists and science enthusiasts believed this claim. It’s commonly known that, however quick the microwave can make a pot noodle, the microwave itself is fairly dangerous. If we were to put our faces inside the microwave screen as it slowly revolved the food around, we would be get enough energy to boil our brains. So we’ve applied this same logic to the water, believing that it too will be harmed, or altered by the microwave. Now you know the answer, it’s your responsibility to tell others that this ‘science experiment’ is a myth.

Answer by Matt Powell

Question from Claire via Facebook

Article by Matthew Powell

June 19, 2013

Matt is a graduate from Oxford, who is interested in the universe and has spent many a night in the bar trying to explain space to disgruntled students. Besides being the meanest ukulele player to grace the English countryside, Matt spends his time reading, writing and walking. He’s also the intern…

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5 thoughts on “Does microwaved water kill plants?”

  1. “If we were to put our faces inside the microwave screen as it slowly revolved the food around, we would be getting an uppercut of very harmful, cancer causing radiation.”

    That isn’t true in the slightest. The wavelengths of EM used in microwaves is not capable of causing DNA damage. It wouldn’t be good for you, as your head would eventually be boiled and explode, but it certainly wouldn’t give you cancer.

  2. Microwave water does NOT kill plants. Purified or distilled water and tap water is not harmful but not much better than microwaved water

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