How Trees Communicate: Chemical Signals, Fungi and Electrical Activity
Trees do not speak, at least not in the human sense, but they exchange information through biochemical and physical signals. These mechanisms can influence nutrient transfers, defence responses and coordinated reactions within plant communities.
These complex signalling systems allow trees to interact with their environment and with many other living organisms. Let us take a closer look at what science has discovered.
Volatile organic compounds (VOCs)
One important form of plant signalling involves volatile organic compounds (VOCs): carbon-based organic molecules that readily evaporate into the air. Trees and other plants release many such compounds. Isoprene, for example, is emitted by numerous tree species and can help protect leaf function under heat stress, including by helping maintain photosynthetic performance.
Terpenes are another major class of VOCs, especially abundant in conifers. They serve many ecological functions, including defence against herbivores and interactions with pollinators; atmospheric terpenes can also contribute to aerosol and cloud formation. During herbivore attacks, neighbouring plants exposed to certain volatile signals may activate defence mechanisms, such as producing compounds that make their tissues less palatable. Some forest VOCs are often discussed under the broad term phytoncides, which I explore further in the dedicated article on this blog.
This leads us to the concept of allelopathy, in which organisms release biochemicals that can affect other organisms. Plant signalling compounds can also originate below ground through root exudates or from decomposing plant material. Such compounds can have a range of positive or negative effects on germination, growth and survival.
As the French National Research Institute for Agriculture, Food and Environment (INRAE) noted in a 2022 publication, trees are not the only organisms that emit and detect volatile compounds. Chemical signalling of this kind is widespread among terrestrial organisms. Examples include insect pheromones, which can attract mates, and kairomones released by one organism and detected by another, for example when insects use plant odours to locate food or shelter.
Volatile compounds are also present in mammalian breath, sweat and urine and may contribute to social and territorial chemical communication.
Below-ground interactions: mycorrhizal networks
Perhaps the most famous form of below-ground interaction involves mycorrhizal networks, popularly nicknamed the forest’s underground internet or the “Wood Wide Web”. Their defining feature is a symbiotic relationship between fungi and plant roots.
In this symbiosis, fungi receive carbon compounds produced through photosynthesis, while plants gain access to fungal networks that can improve uptake of water and mineral nutrients from the soil.
I explore these remarkable networks in more detail in a dedicated article on this blog. They remain an active field of research, including the work of US evolutionary biologist Toby Kiers. In early 2026, Kiers received the Tyler Prize for Environmental Achievement, sometimes described as the environmental equivalent of a Nobel Prize. Her work emphasises that mycorrhizal fungi are not merely useful partners of plants but part of one of the planet’s major biological circulation systems.
Research involving Kiers and colleagues has helped quantify how much plant-derived carbon moves below ground into mycorrhizal fungi. One global estimate suggested around 13.12 billion tonnes of CO₂-equivalent carbon flow per year, illustrating the enormous scale of below-ground carbon allocation. Such estimates carry uncertainty and should not be interpreted as a simple permanent carbon sink.
Electrical signals
VOCs and mycorrhizal networks are not the only signalling mechanisms in plants. Trees and other plants also produce measurable electrical signals within their tissues.
These include slow biological electrical signals, generated by ion movements that temporarily change membrane potential. Plant electrophysiology studies how such signals travel through tissues and contribute to rapid responses to external stimuli, particularly environmental stress.
Plant electrophysiology draws on techniques also used in animal physiology and, over the past decades, has opened the door to practical applications, as discussed in work by Alexander Volkov of Oakwood College in Huntsville, United States, published in the field of plant electrophysiology in 2006.
This field contributes to research on plant-based biosensors and environmental monitoring, including detection of responses to pollutants, pesticides and other stresses, climate-related monitoring and plant–insect interactions. In agriculture, electrical and physiological signals are also being explored as tools for crop monitoring.
Trees still have so much to teach us
Reading about nature is one step. Experiencing it through the body and the senses is another. Direct contact with trees can create space to slow down, feel grounded and look at our own lives with greater clarity.
If this article has made you want to go further, I invite you to discover my forest therapy walks: immersive experiences designed to slow down, reconnect and pay closer attention to the intelligence of living systems.
And for those drawn to a deeper, more spiritual approach, the spiritual forest therapy training offers a unique learning space: a sensory, symbolic and energetic exploration of the relationship between people and trees, both for personal experience and for guiding others.
The trees are there. Sometimes all it takes is one step to find our way back towards the plant world.
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