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.
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.
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.
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.
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.
Watching my 4-month-old grandson delight in standing in his new walker, I am reminded that there are no “overnight successes” or “quick fixes” in the real world. Babies take months to learn how to stand and walk. Gardens take years to fulfill their creators’ dreams. Every success we experience, be it in our professions, health and fitness, or in the garden, all happen because of baby steps taken over and over again.
Little steps add up
In 2016, my son and I walked across Spain. That was a one-month, 500-mile walk. It was a wonderful experience, and not just because I got to do it with him. Learning first-hand that taking one step after another, no matter how casually, will eventually add up to something significantly bigger. Your garden and landscape work the same way.
Plans, passions, and reality
Most gardeners, especially those new to gardening, would love to have that picture-perfect, trouble-free, highly productive piece of earth seen in movies and magazines. The reality is, elegant botanical gardens have dozens of professional gardeners and countless volunteers who work every day to create those masterpieces. For us home gardeners, getting help like that is nearly impossible. It’s hard enough to find someone to help dispose of an old couch. [And many of those magazine garden, plant, and flower pictures are photoshopped.]
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.
“Natural is better.”
“Natural is safer.”
These words are easy to say and they sound good, but they can be very wrong. You can’t assume that just because something is natural means it is safe.
Natural pesticides can be just as deadly as chemical concoctions. Mushrooms may be natural and organic, but some of them can kill you. Even the seeds and skins of some of our common foods can cause illness or death when eaten to excess.
Chemical warfare may be banned in the human world (and with good reason), but plants regularly employ chemicals to defend against insect and herbivore feeding and in response the injury and environmental stresses. Some of the chemicals they use can hurt us, too.
Today we are looking at some of the natural toxins growing in our gardens and lurking in our crisper drawers.
Apples, barley, and stone fruits
The seeds of apples and the pits of stone fruits contain cyanogenic glycoside. When plants feel they are being attacked, they remove the sugar molecule from these compounds, converting them into hydrogen cyanide. Barley, flax, and sorghum do the same thing. Raw cassava (tapioca) and bamboo shoots also contain hydrogen cyanide. Hydrogen cyanide is a blood agent that halts cellular respiration. It will kill you if you eat too much.
Cereals, dried fruits, nuts, and spices
Have you ever nibbled raw cookie dough? I have. And I’ve heard that I shouldn’t. I always thought that was because of the raw eggs, but it ends up that bird poop residue is the real reason. Another problem with this food group is more serious than a short-term belly ache. Cereals, dried fruits, nuts, and spices can harbor certain molds, called mycotoxins, that can cause severe illness. Long-term exposure, while rare, can cause immune deficiency and some cancers.
Herbs, honey, and sunflowers
Herbs, honey, and members of the sunflower family all contain something called pyrrolizidine alkaloids. Milk, eggs, and cereal grains also contain these chemicals, which are known to cause liver damage. Borage leaf, coltsfoot, and comfrey contain particularly high levels of this natural toxin. Remember, the damage is in the dose.
Raw kidney beans are dangerous. There, I’ve said it. I didn’t even know it until I wrote this post. It ends up that all raw beans contain chemicals called lectins. Lectins can cause severe digestive upset. Raw kidney beans contain more lectins than other beans. Low and slow cooking may be great for that pot roast, but those temperatures may not be high enough to destroy lectins, so be sure to crank up the heat for at least part of your bean cooking regime.
Some people can forage safely for mushrooms and others cannot. I’m in the latter group. Because some mushroom species can kill you, I opt for the grocery store. Unlike some other toxins, those found in mushrooms are not destroyed by cooking.
Parsnips have a chemical arsenal of their own. When they feel threatened, they produce chemicals known as furocoumarins. These chemicals can cause stomachache and skin rashes. To avoid these problems, peel your parsnips and discard any damaged bits. And pour the cooking water down the drain, rather than adding it to your soup stock. By the way, carrots, parsley, celery root, and citrus contain furocoumarins, too.
We’ve all seen it. Just under the brown skin of a potato, you see green. These green areas occur when a potato is sprouting and when the plant feels stressed. Along with that green tinge are chemicals known as glycoalkaloids. All members of the nightshade family contain these chemicals. Mostly found in the leaves, glycoalkaloids can give you a bad belly ache. They can also kill you. Be sure to remove any green or damaged bits before cooking your potatoes. If they taste bitter, toss them in the trash.
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 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.
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.
The plants you see on TV and in magazines always look amazing and perfect and it’s not real. Real plants rarely have perfectly rounded shapes or masses of fruit and flowers wherever you look. In real life, plants often have one side that looks and performs better. Things are uneven. The movie star plants, like their human counterparts, are often airbrushed and staged by professionals.
Imperfections are perfectly normal in the plant (and human) world. Failing to thrive is something else altogether.
Failure to thrive is not a disease. It is a symptom. And most of us have seen it happen in our gardens or on our patios. Scraggly stems, too few leaves, little or no fruit or flowers, and overall weakness are all signs of failing to thrive. In many cases, you can correct the problem and help your plant return to good health. Failure to thrive can be caused by environmental conditions or biological characteristics.
Biological causes of failure to thrive
Some plants are born weak. This can be because the seed was old, or germination occurred too early in the season while temperatures were too cold. In both cases, the seedling had to put out more energy than it could afford early in its growth and may never recover fully. Other biologic causes of failure to thrive include bacterial, fungal, and viral diseases, girdling roots,
You can prevent many problems with these tips:
Environmental causes behind failure to thrive
Plants cannot leave their environment, so they have to deal with wherever they are. There are several environmental conditions that keep plants from thriving:
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.
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!
Kate Russell, writer, gardener, and so much more.