We all think of plants as silent, but they're not. 🌱

Plant bioacoustics is the study of how plants generate and respond to sound. Turns out, plants aren't silent at all. It's just that the sounds they make are outside our hearing range, mostly being ultrasound.

Plants which are distressed by lack of water even squeal at around 20-100 kHz. We can't hear that, but some animals can. Moths will even avoid these distressed plants and lay their eggs on healthier leaves.

There's also a lot of evidence that plants do respond to sound. Some seedlings grow their roots towards low frequency sounds. Other plants change their growth behaviour based on other plants nearby, even when kept completely isolated with sound as the only way of knowing that each other are there.

So maybe talking and playing music to your plants is worth doing after all. Who knows?

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Here are some other things to read:

• "Sound Garden: Can Plants Actually Talk and Hear?"

• "It Turns Out Plants Make Noise as They Grow"

• "Recordings reveal that plants make ultrasonic squeals when stressed"

• Wikipedia: Plant Bioacoustics

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@InvaderXan Do you have references for these interesting facts?

do lettuce plants scream when being harvested? omg, I'll become a fruitarian

@StroomAfwaarts I suspect most plants have some reaction to being harvested, even when picking fruit. As I tell everyone else, the important part is having respect for the plant while it's still growing. And remembering that it's still alive even after you bring it to your kitchen.

@InvaderXan That is very interesting, but also quite depressing... Now I feel even sorry-er for the times when I forgot to give them water :blobnervous:

@shad Gives you a reason to remember next time though!

@InvaderXan plants is just very slow cause theyre solar powered and have to be energy efficient

@InvaderXan slow in the relative sense :p do u wonder if they percieve time the same as us, or even at all?

@nohomosuperior Now that's an interesting question. It's hard to know how or if plants *perceive* time, but they definitely have day-night rhythms. Some plants do "sleep" at night.

Sensitive plants are interesting this way. At night, they fold their leaves up. The lights in my apartment are on daily timers. I used to have a plant which would go to sleep sometimes, even if the lights were still on for whatever reason.

@InvaderXan just sleepy i guess! And oh right thats true hmm
Ive been thinking about plant and fungus aliens for a while is all lol

@InvaderXan what!!? Really!!? Holy cow that’s awesome, I had no idea. I wonder how that could be recorded without special fancy expensive gear...

@cb In theory, all you'd need is a microphone with response at the right frequencies (though I have no idea how much they would cost). Then you could use software to pitch shift anything they recorded down to audible frequencies. Audacity is free software which can do that, though I'm not sure how well it works at those frequencies.

@InvaderXan can we apply this knowledge to developing a mechanism that can sense my potted green babies saying they're thirsty, and automatically watering them and logging the frequency & timestamps of noises and waterings?

@maidofclay You know, I'm sure this is possible. Or, more simply, just so you can hear them and know when they need to be watered. It would be interesting being able to hear all the plants in my apartment!

@InvaderXan but also, tuned so as to not hear all the plants outside. I don't want to set it too sensitive and just hear an endless chorus of screaming trees and grass.

@maidofclay Should't be too difficult with the right kind of microphone, I think? Assuming the ultrasonic ones work the same way as stage mics. Which admittedly, I have no idea about!

@InvaderXan Why does everyone hate on The Happening? It’s not amazing or anything, but it’s not as bad as people say.

@InvaderXan As someone who used to be able to hear ~22khz in a sufficiently quiet environment, this explains some of my experiences during a drought one summer as a child.

(By the time my hearing range was tested I topped out at 22khz, but that was when I was about 13, and it wouldn't surprise me if it had been even higher when I was a child.)

@artsyhonker Oh, that's interesting. So you could actually hear them? I'm curious, would you mind telling me a little more?

I grew up in the countryside so every day was constantly full of the sounds of birds and insects during warmer months. Thinking back, I wonder if I ever heard plants without realising what I was hearing.

@InvaderXan I remember a few times being absolutely certain that the trees were fizzing. It was only that summer, and only on very still, very hot days, and it was pretty quiet.

When I told my father about it he thought I was being poetic.

@InvaderXan It could well have been an insect or something. It didn't sound like the ones I know, but I don't know very many insect sounds.

@artsyhonker So I'm really quite late replying to this, but one of the mechanisms we know of which lets plants make sound is the formation of bubbles inside their veins. Bubbles make noise as they form and as they collapse. Apparently, some people use this as a way of assessing plant health. So there's a good chance that you absolutely did hear the trees fizzing!

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