Back when I was young and lacking enough sense to research facts before spouting Old Wives Tales, I used to tell everyone that plants grown around classical music would thrive while their twins, who had been exposed to heavy metal, would wither and die. It’s simply not true.


What is true is far more fascinating.


The sound of silence

We expect plants to be quiet. We’re not surprised when a seedling silently reaches for the sun. [Corn and bamboo can be exceptions to that quiet.] No matter how closely we listen, we cannot hear roots as they reach deep into the soil.


You can track down videos and products that translate these biological processes of plants into sounds and music, but that’s not what we’re talking about here. Today’s topic is about the perception and production of actual sounds.


Responding to sounds

Somehow, without brains, ears, eyes, noses, or nervous systems, plants can perceive, respond to, and communicate visual cues, aromas, gravity, and sounds to other plants. [Did you know that even bacteria communicate with one another through sound vibrations? I didn’t either.]


Many plants respond to the sound of caterpillars and other herbivores feeding by producing protective chemicals. Sound waves have also been shown to increase growth rates within some plants. One study found that sound wave treatments of 125 and 250 Hz increased drought tolerance in rice (Jeong, et al 2008). Detecting certain frequencies can also cause plants to produce growth hormones and protect themselves against microbial pathogens.


Plant bioacoustics

The technical term for a plant’s ability to perceive and produce sounds is ‘plant bioacoustics’. They can produce sounds in the 10–240 Hz range, as well as ultrasonic acoustic emissions (UAE) within 20–300 kHz. [We hear sounds in the 20 to 20,000 Hz range.] The sound frequencies plants produce vary, depending on the cause behind the need to communicate. These sounds are produced in the xylem, where water and bubbles of air are moved around. Scientists believe that plants produce sounds by manipulating these bubbles, something my fellow barbershop chorus friends will appreciate. In the plant world, this bubbling is called cavitation.


It ends up that plants really do “scream” when they are damaged. Did you know that tomato plants stressed by drought produce an average of 35 sounds each hour? The same plants produce 11 sounds an hour when stressed by stem damage. And those sounds are different, in both volume and frequency, depending on the cause and the species of the affected plant. Apparently, drought stress is grounds for louder communication.


Social interactions

We know that plants can detect neighboring plants by touch. We also know that they use chemical messaging to orchestrate exchanges with soil microorganisms, trading sugars produced through photosynthesis for specific nutrients. Trees and other plants recognize family members and create social networks.


If you had the proper equipment, and many mammals and insects do, you’d be able to hear those tomato plants from up to 16 feet away. It’s much noisier in my garden than I ever realized. And it’s happening underground, too.


Root signaling

It ends up that it takes very little energy to send sound waves through the soil. When root cells are damaged, plants generate sounds that can be detected by neighboring plants, warning them that danger may be at hand. Plants also produce sounds in the 100–300 Hz range that tell their neighbors where good food and water can be found. Your pea plant roots are actively listening for the sound of water in the soil.


Buzz pollination

Some insects use sound vibrations to make plants release their pollen. This is called buzz pollination or sonication. You can test this with a tuning fork. Depending on the plant species, sound waves between 40 to 1000 Hz cause flowers to expel small doses of pollen into the air. Other flowers detect the frequencies of certain bee wingbeats and respond by producing nectar that contains more sugar.


We still don’t know how plants perceive sound.


But researchers are currently exploring ways of using sound waves to help plants be more productive while protecting them from insect feeding. One study used sound to increase tomato crops by 13%. Wouldn’t it be nice if we could keep aphids, stink bugs, and weeds away while encouraging bigger, sweeter tomatoes? It just might happen. They are also exploring ways of use sound to reduce ethylene production so that produce is less likely to rot on the way to market.


Can plants hear? They sure can. Does talking to them make them grow better? It just might.

But you can take your passion for gardening and your ideals and get them moving in the right direction by identifying and performing short-term goals regularly and consistently. Baby steps. Say you want a lush, productive blueberry hedge? Start by identifying the best location. Clear away the weeds. Top-dress the area with aged manure and compost. Protect the space with mulch. Conduct research about the best varieties for your microclimate. Eventually, you will install your blueberry plants. And, after a few years and regular care, your blueberry hedge will become a reality. It won’t happen overnight, but those baby steps can and will get you there.


Little doesn’t mean insignificant

Unless we’re talking about diamonds (and babies), small things are often seen as less-than. The truth is, it’s the little things, done repeatedly, that create practically every success. None of us is perfectly fit two months after our New Year's’ resolutions are made. But try adding squats while your microwave is running, or 10 little jumping jacks each time you use the bathroom and see just how much these tiny acts of fitness add up over time. The trick is making these baby steps easy enough to do that there’s no desire to avoid them.


Trying to rid your yard of every weed in a single day is a Herculean task that may make you throw up your hands in despair and quit gardening altogether. Weeding your garden on a regular rotation will never get rid of all your weeds (nothing can do that short of Agent Oranging the neighborhood). What it will do is ensure that you are checking on each area of your garden regularly and removing most of the weeds. Over time, the weeds will be less of a problem and you won’t experience burn-out.

Rhubarb

I’m only including rhubarb because everyone seems to have heard how toxic their leaves are. They do contain oxalic acid. It’s also true that oxalic acid can cause cramps and interfere with breathing and heartbeats. It can also cause coma and death, but you’d have to eat a profound amount of rhubarb leaves to have a problem.


Sweet potatoes

Sweet potatoes can produce toxins used in defense against injury, insect feeding, and other stresses. One of these toxins, ipomeamarone, makes your sweet potatoes taste bitter. It can also kill you, so don’t eat bitter-tasting sweet potatoes and always cut out and discard damaged areas.


Zucchini

Bitter-tasting zucchinis may contain chemicals known as cucurbitacins. Cucurbitacins cause something called “toxic squash syndrome”. Symptoms of this condition include severe digestive upset followed by hair loss, weeks after the fact. How weird is that?


With all these potential toxins in our food, what’s a gardener to do?

First of all, recognize that you would have to eat an awful lot of most of these plants to cause any real harm. Second, keeping your plants healthy with proper fertilizing, irrigation, and pest and disease control reduces their need for self-defense.


You can protect yourself and your family by discarding any produce that is badly damaged or moldy and cooking your food properly.

Drastic measures

In some cases, drastic measures are called for. After all your other treatments and corrections have failed, it is time to dig up or unpot your plants and get to the root of the problem. You will want to work over a tarp or very large container. Either dig up your problem plant or remove it from its container. Then, shake the soil from the roots and wash them. Root washing is an excellent way to see what, exactly, has been going on underground. Prune out any damaged, mushy, broken, or infected roots. Set the root ball in a bucket of water and examine the soil. Look for signs of insect pupae, grubs, root maggots, root weevils, wireworms, cutworms, and other soil-dwelling pests.


Smell the soil. Does it smell rich and earthy? Or it smell funky, like old gym socks? Healthy soil contains earthworms and zillions of microorganisms and it smells like good earth. Less than ideal soil smells like something went bad. If that’s the case, toss it out and give your patient some fresh potting soil. Until your plant is thriving, if possible, it is best to keep it in a container during its recovery.

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Do you have a plant that’s failing to thrive? Tell us about it in the comment and let’s see if we can help it get better!