Most people find talking to plants to be amusing, as though conversing with a tomato could coax it into heavier production. We also smile at reports of music being played to plants, mostly soothing in nature, under the assumption that a calm, happy plant is a productive plant.
Can plants really hear? Should we spend time in the yard talking to our trees, shrubs and vegetables, or possibly singing to the zinnias?
Investigating whether plants respond to certain genres of music or tones of speech makes for fun school science projects, but those quick tests aren’t intended to demonstrate the effects of sound on plants like a replicated controlled scientific research study can do.
One of the earliest such studies was done in 1962 at India’s Annamalai University, where balsam plants exposed to classical music reportedly had a 20% increase in growth rate, with a 72% increase in biomass. After experimenting with various instruments, researchers concluded the violin was the most effective. Similar results were found by Canadian engineer Eugene Canby, whose wheat fields experienced a 66% yield increase when exposed to recordings of Bach’s "Violin Sonata."
So why isn’t Bach being broadcast over every wheat field in the Upper Midwest? Many plant scientists have criticized previous experiments as being scientifically flawed, with too many variables that weren’t properly managed, such as light, water, air pressure and soil conditions. If the results can’t be reliably duplicated, then musical recommendations are pointless.
Other interesting projects include a 2014 study at India’s Osmania University that demonstrated improved production on 30 rose bushes exposed to classical music as compared to silence or other music genres. In 2007, South Korea’s National Institute of Agricultural Biotechnology identified plant genes that respond to music after rice plants responded favorably to Beethoven’s "Moonlight Sonata."
Scientists have barely scratched the surface, and research is beginning to show that plants are more high-tech than simply enjoying pleasant sounds. Research at Israel’s Tel Aviv University showed that when primrose flowers were exposed to recorded sounds of a flying bee, the flowers produced 20% sweeter nectar within three minutes. The increased sweetness was thought to be a deliberate, timed action to persuade a visit by a nearby bee, which then accomplishes pollination for the inventive flower.
A 2014 study reported in Scientific American showed that when rockcress plants were exposed to a recording of a caterpillar chewing on rockcress leaves, the plants produced a chemical that made the leaves less palatable. The possibility exists in nature that when a rockcress plant “hears” a neighboring plant being consumed by a caterpillar, it produces toxins in self-preservation.
Without ears, how do plants hear sounds? Researchers believe plants respond to sound wave vibrations, but studying the exact mechanism has been difficult with plants because they don’t have a hearing organ, as animals and humans do.
Such research could be used to improve plant growth in the future. In a recent article published in Frontiers in Plant Science, the journal of the National Center for Biotechnology Information, scientists say sound recordings can be used to promote plant growth in several ways. Recordings can stimulate growth hormones to produce larger plants and can enhance photosynthesis genes.
Some sounds can help plants defend against pathogens by activating internal chemicals. Sound can even be used to encourage drought tolerance in plants by changing the elasticity and flexibility of the cell wall to reduce water loss and wilting.
What about talking to our plants? Researchers and horticulturists suggest that people who offer verbal affection to their plants are probably more likely to care for the plants in other important ways, such as by remembering to water them and give them light and fertilizer, and tend to them attentively.
Don Kinzler, a lifelong gardener, is the horticulturist with North Dakota State University Extension for Cass County. Readers can reach him at email@example.com.