Wild About Plant Communication

If a tree speaks in the forest, can anybody hear?

When it comes to communication, we tend to think of species on a continuum. We view ourselves as the ‘best’ communicators at one of a scale that moves through apes, dolphins, and the other mammals before landing on species such as plants and fungi on the opposite side. When it comes to language, our main means of communication, this assumption is probably correct. However, in the past few years, new evidence has emerged that suggests that we need to change the way we think about communication in plants.

While they may not have language in the way that we understand it, plants are complex communicators. One of the key ways that plants communicate is through the release of chemicals, known as volatile organic compounds. These chemicals are often released when a plant is under duress, such as when it’s being attacked by pests or predators. The smell of cut grass when you mow your lawn? It’s not mulched pieces of grass you’re smelling. It’s compounds released by your lawn, telling other species it’s in distress.

A lawn mower on a partially cut lawn.
The smell of fresh-cut grass is a distress signal. Photo by Prasannanossam3, CC BY-SA 4.0, via Wikimedia Commons

These chemicals are more than a warning system. They also attract beneficial insects. When maize is attacked by a certain type of worm, the compounds it releases attract the worm’s natural predator. Similarly, the fragrance emitted from flowers also acts to attract pollinators, another form of communication that benefits the plants.

There is also scientific evidence that trees use fungal networks to communicate. Working in the coastal Douglas-fir forests of British Columbia, Dr. Suzanne Simard discovered that trees communicate using a vast matrix of fungi beneath the soil. Simard’s research confirmed what Indigenous peoples already knew: that these trees are part of a complex, interconnected system. 

A forest of coastal Douglas-fir trees. The tree trunks are covered in moss. In the foreground, a fallen tree lies amid a bed of ferns.
Coastal Douglas-fir forests communicate through vast fungal networks. Photo by Sang Trinh, CC BY 2.0, via Wikimedia Commons

A concept that underpins traditional indigenous knowledge but that is often missing from Western science, is the idea that everything is connected. Western science often seeks to understand complex ecosystems by taking them apart and analyzing the discrete components in a reductionist fashion rather than trying to understand the whole. It’s rather like dismantling a car and using the parts to try to understand a road network without looking at a map. If we step back, it seems like common sense to know that a tree grown in a lab will respond differently than a tree in a natural forest or that a 500-year-old cedar will interact differently within its environment. Despite this, Western science often insists on isolation as the pathway to the natural world. 

Research about plant communication is controversial. Even today, Western science relies on a hierarchical view of nature that assumes humans are exceptional and casts doubt on concepts such as communication in plants or emotions in animals. Perhaps our desire to isolate plants to force them to speak is getting in the way of our ability to see the communication within a complex system. 

Our understanding of plants continues to evolve. A South American vine (Boquila trifoliolata) was discovered to be able to shape-shift, changing its leaves to match those of the surrounding vegetation. Which begs an obvious question. How does this plant know what the other leaves look like? Initial theories suggested that Boquila was receiving chemical cues from its neighbours – an advanced form of interspecies communication. However, a recent lab experiment threw that theory, plus many of our assumptions about plants, into question when Boquila shifted its leaves to mimic an artificial plant. More research is needed, but Boquila may force us to grapple with a ground-breaking question. What if plants can’t only talk, what if they can see?

A vine with three-lobed leaves climbs a small tree trunk.
Boquila in its natural form. Photo by Inao, CC BY-SA 2.0, via Wikimedia Commons